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![Linus Torvalds](/assets/img/avatar_default.png)
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6: fs: simplify iget & friends fs: pull inode->i_lock up out of writeback_single_inode fs: rename inode_lock to inode_hash_lock fs: move i_wb_list out from under inode_lock fs: move i_sb_list out from under inode_lock fs: remove inode_lock from iput_final and prune_icache fs: Lock the inode LRU list separately fs: factor inode disposal fs: protect inode->i_state with inode->i_lock autofs4: Do not potentially dereference NULL pointer returned by fget() in autofs_dev_ioctl_setpipefd() autofs4 - remove autofs4_lock autofs4 - fix d_manage() return on rcu-walk autofs4 - fix autofs4_expire_indirect() traversal autofs4 - fix dentry leak in autofs4_expire_direct() autofs4 - reinstate last used update on access vfs - check non-mountpoint dentry might block in __follow_mount_rcu()
3295 lines
86 KiB
C
3295 lines
86 KiB
C
/*
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* linux/fs/buffer.c
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*
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* Copyright (C) 1991, 1992, 2002 Linus Torvalds
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*/
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/*
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* Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
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*
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* Removed a lot of unnecessary code and simplified things now that
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* the buffer cache isn't our primary cache - Andrew Tridgell 12/96
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*
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* Speed up hash, lru, and free list operations. Use gfp() for allocating
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* hash table, use SLAB cache for buffer heads. SMP threading. -DaveM
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*
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* Added 32k buffer block sizes - these are required older ARM systems. - RMK
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*
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* async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
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*/
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#include <linux/kernel.h>
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#include <linux/syscalls.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/percpu.h>
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#include <linux/slab.h>
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#include <linux/capability.h>
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#include <linux/blkdev.h>
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#include <linux/file.h>
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#include <linux/quotaops.h>
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#include <linux/highmem.h>
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#include <linux/module.h>
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#include <linux/writeback.h>
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#include <linux/hash.h>
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#include <linux/suspend.h>
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#include <linux/buffer_head.h>
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#include <linux/task_io_accounting_ops.h>
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#include <linux/bio.h>
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#include <linux/notifier.h>
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#include <linux/cpu.h>
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#include <linux/bitops.h>
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#include <linux/mpage.h>
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#include <linux/bit_spinlock.h>
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static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
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#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
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inline void
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init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
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{
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bh->b_end_io = handler;
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bh->b_private = private;
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}
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EXPORT_SYMBOL(init_buffer);
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static int sleep_on_buffer(void *word)
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{
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io_schedule();
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return 0;
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}
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void __lock_buffer(struct buffer_head *bh)
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{
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wait_on_bit_lock(&bh->b_state, BH_Lock, sleep_on_buffer,
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TASK_UNINTERRUPTIBLE);
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}
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EXPORT_SYMBOL(__lock_buffer);
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void unlock_buffer(struct buffer_head *bh)
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{
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clear_bit_unlock(BH_Lock, &bh->b_state);
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smp_mb__after_clear_bit();
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wake_up_bit(&bh->b_state, BH_Lock);
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}
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EXPORT_SYMBOL(unlock_buffer);
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/*
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* Block until a buffer comes unlocked. This doesn't stop it
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* from becoming locked again - you have to lock it yourself
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* if you want to preserve its state.
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*/
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void __wait_on_buffer(struct buffer_head * bh)
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{
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wait_on_bit(&bh->b_state, BH_Lock, sleep_on_buffer, TASK_UNINTERRUPTIBLE);
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}
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EXPORT_SYMBOL(__wait_on_buffer);
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static void
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__clear_page_buffers(struct page *page)
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{
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ClearPagePrivate(page);
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set_page_private(page, 0);
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page_cache_release(page);
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}
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static int quiet_error(struct buffer_head *bh)
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{
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if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit())
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return 0;
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return 1;
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}
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static void buffer_io_error(struct buffer_head *bh)
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{
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char b[BDEVNAME_SIZE];
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printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
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bdevname(bh->b_bdev, b),
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(unsigned long long)bh->b_blocknr);
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}
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/*
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* End-of-IO handler helper function which does not touch the bh after
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* unlocking it.
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* Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
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* a race there is benign: unlock_buffer() only use the bh's address for
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* hashing after unlocking the buffer, so it doesn't actually touch the bh
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* itself.
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*/
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static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
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{
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if (uptodate) {
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set_buffer_uptodate(bh);
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} else {
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/* This happens, due to failed READA attempts. */
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clear_buffer_uptodate(bh);
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}
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unlock_buffer(bh);
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}
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/*
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* Default synchronous end-of-IO handler.. Just mark it up-to-date and
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* unlock the buffer. This is what ll_rw_block uses too.
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*/
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void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
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{
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__end_buffer_read_notouch(bh, uptodate);
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put_bh(bh);
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}
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EXPORT_SYMBOL(end_buffer_read_sync);
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void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
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{
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char b[BDEVNAME_SIZE];
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if (uptodate) {
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set_buffer_uptodate(bh);
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} else {
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if (!quiet_error(bh)) {
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buffer_io_error(bh);
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printk(KERN_WARNING "lost page write due to "
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"I/O error on %s\n",
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bdevname(bh->b_bdev, b));
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}
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set_buffer_write_io_error(bh);
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clear_buffer_uptodate(bh);
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}
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unlock_buffer(bh);
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put_bh(bh);
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}
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EXPORT_SYMBOL(end_buffer_write_sync);
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/*
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* Various filesystems appear to want __find_get_block to be non-blocking.
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* But it's the page lock which protects the buffers. To get around this,
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* we get exclusion from try_to_free_buffers with the blockdev mapping's
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* private_lock.
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*
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* Hack idea: for the blockdev mapping, i_bufferlist_lock contention
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* may be quite high. This code could TryLock the page, and if that
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* succeeds, there is no need to take private_lock. (But if
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* private_lock is contended then so is mapping->tree_lock).
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*/
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static struct buffer_head *
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__find_get_block_slow(struct block_device *bdev, sector_t block)
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{
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struct inode *bd_inode = bdev->bd_inode;
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struct address_space *bd_mapping = bd_inode->i_mapping;
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struct buffer_head *ret = NULL;
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pgoff_t index;
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struct buffer_head *bh;
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struct buffer_head *head;
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struct page *page;
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int all_mapped = 1;
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index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
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page = find_get_page(bd_mapping, index);
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if (!page)
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goto out;
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spin_lock(&bd_mapping->private_lock);
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if (!page_has_buffers(page))
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goto out_unlock;
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head = page_buffers(page);
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bh = head;
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do {
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if (!buffer_mapped(bh))
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all_mapped = 0;
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else if (bh->b_blocknr == block) {
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ret = bh;
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get_bh(bh);
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goto out_unlock;
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}
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bh = bh->b_this_page;
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} while (bh != head);
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/* we might be here because some of the buffers on this page are
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* not mapped. This is due to various races between
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* file io on the block device and getblk. It gets dealt with
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* elsewhere, don't buffer_error if we had some unmapped buffers
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*/
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if (all_mapped) {
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printk("__find_get_block_slow() failed. "
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"block=%llu, b_blocknr=%llu\n",
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(unsigned long long)block,
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(unsigned long long)bh->b_blocknr);
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printk("b_state=0x%08lx, b_size=%zu\n",
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bh->b_state, bh->b_size);
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printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits);
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}
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out_unlock:
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spin_unlock(&bd_mapping->private_lock);
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page_cache_release(page);
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out:
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return ret;
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}
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/* If invalidate_buffers() will trash dirty buffers, it means some kind
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of fs corruption is going on. Trashing dirty data always imply losing
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information that was supposed to be just stored on the physical layer
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by the user.
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Thus invalidate_buffers in general usage is not allwowed to trash
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dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to
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be preserved. These buffers are simply skipped.
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We also skip buffers which are still in use. For example this can
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happen if a userspace program is reading the block device.
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NOTE: In the case where the user removed a removable-media-disk even if
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there's still dirty data not synced on disk (due a bug in the device driver
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or due an error of the user), by not destroying the dirty buffers we could
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generate corruption also on the next media inserted, thus a parameter is
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necessary to handle this case in the most safe way possible (trying
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to not corrupt also the new disk inserted with the data belonging to
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the old now corrupted disk). Also for the ramdisk the natural thing
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to do in order to release the ramdisk memory is to destroy dirty buffers.
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These are two special cases. Normal usage imply the device driver
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to issue a sync on the device (without waiting I/O completion) and
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then an invalidate_buffers call that doesn't trash dirty buffers.
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For handling cache coherency with the blkdev pagecache the 'update' case
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is been introduced. It is needed to re-read from disk any pinned
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buffer. NOTE: re-reading from disk is destructive so we can do it only
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when we assume nobody is changing the buffercache under our I/O and when
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we think the disk contains more recent information than the buffercache.
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The update == 1 pass marks the buffers we need to update, the update == 2
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pass does the actual I/O. */
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void invalidate_bdev(struct block_device *bdev)
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{
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struct address_space *mapping = bdev->bd_inode->i_mapping;
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if (mapping->nrpages == 0)
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return;
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invalidate_bh_lrus();
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lru_add_drain_all(); /* make sure all lru add caches are flushed */
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invalidate_mapping_pages(mapping, 0, -1);
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}
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EXPORT_SYMBOL(invalidate_bdev);
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/*
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* Kick the writeback threads then try to free up some ZONE_NORMAL memory.
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*/
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static void free_more_memory(void)
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{
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struct zone *zone;
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int nid;
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wakeup_flusher_threads(1024);
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yield();
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for_each_online_node(nid) {
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(void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
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gfp_zone(GFP_NOFS), NULL,
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&zone);
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if (zone)
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try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
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GFP_NOFS, NULL);
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}
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}
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/*
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* I/O completion handler for block_read_full_page() - pages
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* which come unlocked at the end of I/O.
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*/
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static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
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{
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unsigned long flags;
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struct buffer_head *first;
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struct buffer_head *tmp;
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struct page *page;
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int page_uptodate = 1;
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BUG_ON(!buffer_async_read(bh));
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page = bh->b_page;
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if (uptodate) {
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set_buffer_uptodate(bh);
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} else {
|
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clear_buffer_uptodate(bh);
|
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if (!quiet_error(bh))
|
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buffer_io_error(bh);
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SetPageError(page);
|
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}
|
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|
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/*
|
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* Be _very_ careful from here on. Bad things can happen if
|
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* two buffer heads end IO at almost the same time and both
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* decide that the page is now completely done.
|
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*/
|
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first = page_buffers(page);
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local_irq_save(flags);
|
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bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
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clear_buffer_async_read(bh);
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unlock_buffer(bh);
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tmp = bh;
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do {
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if (!buffer_uptodate(tmp))
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page_uptodate = 0;
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if (buffer_async_read(tmp)) {
|
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BUG_ON(!buffer_locked(tmp));
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goto still_busy;
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}
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tmp = tmp->b_this_page;
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} while (tmp != bh);
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bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
|
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local_irq_restore(flags);
|
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|
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/*
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* If none of the buffers had errors and they are all
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* uptodate then we can set the page uptodate.
|
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*/
|
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if (page_uptodate && !PageError(page))
|
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SetPageUptodate(page);
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unlock_page(page);
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return;
|
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still_busy:
|
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bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
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local_irq_restore(flags);
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return;
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}
|
|
|
|
/*
|
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* Completion handler for block_write_full_page() - pages which are unlocked
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* during I/O, and which have PageWriteback cleared upon I/O completion.
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*/
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void end_buffer_async_write(struct buffer_head *bh, int uptodate)
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{
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char b[BDEVNAME_SIZE];
|
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unsigned long flags;
|
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struct buffer_head *first;
|
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struct buffer_head *tmp;
|
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struct page *page;
|
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|
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BUG_ON(!buffer_async_write(bh));
|
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|
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page = bh->b_page;
|
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if (uptodate) {
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set_buffer_uptodate(bh);
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} else {
|
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if (!quiet_error(bh)) {
|
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buffer_io_error(bh);
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printk(KERN_WARNING "lost page write due to "
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"I/O error on %s\n",
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bdevname(bh->b_bdev, b));
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}
|
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set_bit(AS_EIO, &page->mapping->flags);
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set_buffer_write_io_error(bh);
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clear_buffer_uptodate(bh);
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SetPageError(page);
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}
|
|
|
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first = page_buffers(page);
|
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local_irq_save(flags);
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bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
|
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|
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clear_buffer_async_write(bh);
|
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unlock_buffer(bh);
|
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tmp = bh->b_this_page;
|
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while (tmp != bh) {
|
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if (buffer_async_write(tmp)) {
|
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BUG_ON(!buffer_locked(tmp));
|
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goto still_busy;
|
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}
|
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tmp = tmp->b_this_page;
|
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}
|
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bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
|
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local_irq_restore(flags);
|
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end_page_writeback(page);
|
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return;
|
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|
|
still_busy:
|
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bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
|
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local_irq_restore(flags);
|
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return;
|
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}
|
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EXPORT_SYMBOL(end_buffer_async_write);
|
|
|
|
/*
|
|
* If a page's buffers are under async readin (end_buffer_async_read
|
|
* completion) then there is a possibility that another thread of
|
|
* control could lock one of the buffers after it has completed
|
|
* but while some of the other buffers have not completed. This
|
|
* locked buffer would confuse end_buffer_async_read() into not unlocking
|
|
* the page. So the absence of BH_Async_Read tells end_buffer_async_read()
|
|
* that this buffer is not under async I/O.
|
|
*
|
|
* The page comes unlocked when it has no locked buffer_async buffers
|
|
* left.
|
|
*
|
|
* PageLocked prevents anyone starting new async I/O reads any of
|
|
* the buffers.
|
|
*
|
|
* PageWriteback is used to prevent simultaneous writeout of the same
|
|
* page.
|
|
*
|
|
* PageLocked prevents anyone from starting writeback of a page which is
|
|
* under read I/O (PageWriteback is only ever set against a locked page).
|
|
*/
|
|
static void mark_buffer_async_read(struct buffer_head *bh)
|
|
{
|
|
bh->b_end_io = end_buffer_async_read;
|
|
set_buffer_async_read(bh);
|
|
}
|
|
|
|
static void mark_buffer_async_write_endio(struct buffer_head *bh,
|
|
bh_end_io_t *handler)
|
|
{
|
|
bh->b_end_io = handler;
|
|
set_buffer_async_write(bh);
|
|
}
|
|
|
|
void mark_buffer_async_write(struct buffer_head *bh)
|
|
{
|
|
mark_buffer_async_write_endio(bh, end_buffer_async_write);
|
|
}
|
|
EXPORT_SYMBOL(mark_buffer_async_write);
|
|
|
|
|
|
/*
|
|
* fs/buffer.c contains helper functions for buffer-backed address space's
|
|
* fsync functions. A common requirement for buffer-based filesystems is
|
|
* that certain data from the backing blockdev needs to be written out for
|
|
* a successful fsync(). For example, ext2 indirect blocks need to be
|
|
* written back and waited upon before fsync() returns.
|
|
*
|
|
* The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
|
|
* inode_has_buffers() and invalidate_inode_buffers() are provided for the
|
|
* management of a list of dependent buffers at ->i_mapping->private_list.
|
|
*
|
|
* Locking is a little subtle: try_to_free_buffers() will remove buffers
|
|
* from their controlling inode's queue when they are being freed. But
|
|
* try_to_free_buffers() will be operating against the *blockdev* mapping
|
|
* at the time, not against the S_ISREG file which depends on those buffers.
|
|
* So the locking for private_list is via the private_lock in the address_space
|
|
* which backs the buffers. Which is different from the address_space
|
|
* against which the buffers are listed. So for a particular address_space,
|
|
* mapping->private_lock does *not* protect mapping->private_list! In fact,
|
|
* mapping->private_list will always be protected by the backing blockdev's
|
|
* ->private_lock.
|
|
*
|
|
* Which introduces a requirement: all buffers on an address_space's
|
|
* ->private_list must be from the same address_space: the blockdev's.
|
|
*
|
|
* address_spaces which do not place buffers at ->private_list via these
|
|
* utility functions are free to use private_lock and private_list for
|
|
* whatever they want. The only requirement is that list_empty(private_list)
|
|
* be true at clear_inode() time.
|
|
*
|
|
* FIXME: clear_inode should not call invalidate_inode_buffers(). The
|
|
* filesystems should do that. invalidate_inode_buffers() should just go
|
|
* BUG_ON(!list_empty).
|
|
*
|
|
* FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
|
|
* take an address_space, not an inode. And it should be called
|
|
* mark_buffer_dirty_fsync() to clearly define why those buffers are being
|
|
* queued up.
|
|
*
|
|
* FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
|
|
* list if it is already on a list. Because if the buffer is on a list,
|
|
* it *must* already be on the right one. If not, the filesystem is being
|
|
* silly. This will save a ton of locking. But first we have to ensure
|
|
* that buffers are taken *off* the old inode's list when they are freed
|
|
* (presumably in truncate). That requires careful auditing of all
|
|
* filesystems (do it inside bforget()). It could also be done by bringing
|
|
* b_inode back.
|
|
*/
|
|
|
|
/*
|
|
* The buffer's backing address_space's private_lock must be held
|
|
*/
|
|
static void __remove_assoc_queue(struct buffer_head *bh)
|
|
{
|
|
list_del_init(&bh->b_assoc_buffers);
|
|
WARN_ON(!bh->b_assoc_map);
|
|
if (buffer_write_io_error(bh))
|
|
set_bit(AS_EIO, &bh->b_assoc_map->flags);
|
|
bh->b_assoc_map = NULL;
|
|
}
|
|
|
|
int inode_has_buffers(struct inode *inode)
|
|
{
|
|
return !list_empty(&inode->i_data.private_list);
|
|
}
|
|
|
|
/*
|
|
* osync is designed to support O_SYNC io. It waits synchronously for
|
|
* all already-submitted IO to complete, but does not queue any new
|
|
* writes to the disk.
|
|
*
|
|
* To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
|
|
* you dirty the buffers, and then use osync_inode_buffers to wait for
|
|
* completion. Any other dirty buffers which are not yet queued for
|
|
* write will not be flushed to disk by the osync.
|
|
*/
|
|
static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
|
|
{
|
|
struct buffer_head *bh;
|
|
struct list_head *p;
|
|
int err = 0;
|
|
|
|
spin_lock(lock);
|
|
repeat:
|
|
list_for_each_prev(p, list) {
|
|
bh = BH_ENTRY(p);
|
|
if (buffer_locked(bh)) {
|
|
get_bh(bh);
|
|
spin_unlock(lock);
|
|
wait_on_buffer(bh);
|
|
if (!buffer_uptodate(bh))
|
|
err = -EIO;
|
|
brelse(bh);
|
|
spin_lock(lock);
|
|
goto repeat;
|
|
}
|
|
}
|
|
spin_unlock(lock);
|
|
return err;
|
|
}
|
|
|
|
static void do_thaw_one(struct super_block *sb, void *unused)
|
|
{
|
|
char b[BDEVNAME_SIZE];
|
|
while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
|
|
printk(KERN_WARNING "Emergency Thaw on %s\n",
|
|
bdevname(sb->s_bdev, b));
|
|
}
|
|
|
|
static void do_thaw_all(struct work_struct *work)
|
|
{
|
|
iterate_supers(do_thaw_one, NULL);
|
|
kfree(work);
|
|
printk(KERN_WARNING "Emergency Thaw complete\n");
|
|
}
|
|
|
|
/**
|
|
* emergency_thaw_all -- forcibly thaw every frozen filesystem
|
|
*
|
|
* Used for emergency unfreeze of all filesystems via SysRq
|
|
*/
|
|
void emergency_thaw_all(void)
|
|
{
|
|
struct work_struct *work;
|
|
|
|
work = kmalloc(sizeof(*work), GFP_ATOMIC);
|
|
if (work) {
|
|
INIT_WORK(work, do_thaw_all);
|
|
schedule_work(work);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
|
|
* @mapping: the mapping which wants those buffers written
|
|
*
|
|
* Starts I/O against the buffers at mapping->private_list, and waits upon
|
|
* that I/O.
|
|
*
|
|
* Basically, this is a convenience function for fsync().
|
|
* @mapping is a file or directory which needs those buffers to be written for
|
|
* a successful fsync().
|
|
*/
|
|
int sync_mapping_buffers(struct address_space *mapping)
|
|
{
|
|
struct address_space *buffer_mapping = mapping->assoc_mapping;
|
|
|
|
if (buffer_mapping == NULL || list_empty(&mapping->private_list))
|
|
return 0;
|
|
|
|
return fsync_buffers_list(&buffer_mapping->private_lock,
|
|
&mapping->private_list);
|
|
}
|
|
EXPORT_SYMBOL(sync_mapping_buffers);
|
|
|
|
/*
|
|
* Called when we've recently written block `bblock', and it is known that
|
|
* `bblock' was for a buffer_boundary() buffer. This means that the block at
|
|
* `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
|
|
* dirty, schedule it for IO. So that indirects merge nicely with their data.
|
|
*/
|
|
void write_boundary_block(struct block_device *bdev,
|
|
sector_t bblock, unsigned blocksize)
|
|
{
|
|
struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
|
|
if (bh) {
|
|
if (buffer_dirty(bh))
|
|
ll_rw_block(WRITE, 1, &bh);
|
|
put_bh(bh);
|
|
}
|
|
}
|
|
|
|
void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
|
|
{
|
|
struct address_space *mapping = inode->i_mapping;
|
|
struct address_space *buffer_mapping = bh->b_page->mapping;
|
|
|
|
mark_buffer_dirty(bh);
|
|
if (!mapping->assoc_mapping) {
|
|
mapping->assoc_mapping = buffer_mapping;
|
|
} else {
|
|
BUG_ON(mapping->assoc_mapping != buffer_mapping);
|
|
}
|
|
if (!bh->b_assoc_map) {
|
|
spin_lock(&buffer_mapping->private_lock);
|
|
list_move_tail(&bh->b_assoc_buffers,
|
|
&mapping->private_list);
|
|
bh->b_assoc_map = mapping;
|
|
spin_unlock(&buffer_mapping->private_lock);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(mark_buffer_dirty_inode);
|
|
|
|
/*
|
|
* Mark the page dirty, and set it dirty in the radix tree, and mark the inode
|
|
* dirty.
|
|
*
|
|
* If warn is true, then emit a warning if the page is not uptodate and has
|
|
* not been truncated.
|
|
*/
|
|
static void __set_page_dirty(struct page *page,
|
|
struct address_space *mapping, int warn)
|
|
{
|
|
spin_lock_irq(&mapping->tree_lock);
|
|
if (page->mapping) { /* Race with truncate? */
|
|
WARN_ON_ONCE(warn && !PageUptodate(page));
|
|
account_page_dirtied(page, mapping);
|
|
radix_tree_tag_set(&mapping->page_tree,
|
|
page_index(page), PAGECACHE_TAG_DIRTY);
|
|
}
|
|
spin_unlock_irq(&mapping->tree_lock);
|
|
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
|
|
}
|
|
|
|
/*
|
|
* Add a page to the dirty page list.
|
|
*
|
|
* It is a sad fact of life that this function is called from several places
|
|
* deeply under spinlocking. It may not sleep.
|
|
*
|
|
* If the page has buffers, the uptodate buffers are set dirty, to preserve
|
|
* dirty-state coherency between the page and the buffers. It the page does
|
|
* not have buffers then when they are later attached they will all be set
|
|
* dirty.
|
|
*
|
|
* The buffers are dirtied before the page is dirtied. There's a small race
|
|
* window in which a writepage caller may see the page cleanness but not the
|
|
* buffer dirtiness. That's fine. If this code were to set the page dirty
|
|
* before the buffers, a concurrent writepage caller could clear the page dirty
|
|
* bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
|
|
* page on the dirty page list.
|
|
*
|
|
* We use private_lock to lock against try_to_free_buffers while using the
|
|
* page's buffer list. Also use this to protect against clean buffers being
|
|
* added to the page after it was set dirty.
|
|
*
|
|
* FIXME: may need to call ->reservepage here as well. That's rather up to the
|
|
* address_space though.
|
|
*/
|
|
int __set_page_dirty_buffers(struct page *page)
|
|
{
|
|
int newly_dirty;
|
|
struct address_space *mapping = page_mapping(page);
|
|
|
|
if (unlikely(!mapping))
|
|
return !TestSetPageDirty(page);
|
|
|
|
spin_lock(&mapping->private_lock);
|
|
if (page_has_buffers(page)) {
|
|
struct buffer_head *head = page_buffers(page);
|
|
struct buffer_head *bh = head;
|
|
|
|
do {
|
|
set_buffer_dirty(bh);
|
|
bh = bh->b_this_page;
|
|
} while (bh != head);
|
|
}
|
|
newly_dirty = !TestSetPageDirty(page);
|
|
spin_unlock(&mapping->private_lock);
|
|
|
|
if (newly_dirty)
|
|
__set_page_dirty(page, mapping, 1);
|
|
return newly_dirty;
|
|
}
|
|
EXPORT_SYMBOL(__set_page_dirty_buffers);
|
|
|
|
/*
|
|
* Write out and wait upon a list of buffers.
|
|
*
|
|
* We have conflicting pressures: we want to make sure that all
|
|
* initially dirty buffers get waited on, but that any subsequently
|
|
* dirtied buffers don't. After all, we don't want fsync to last
|
|
* forever if somebody is actively writing to the file.
|
|
*
|
|
* Do this in two main stages: first we copy dirty buffers to a
|
|
* temporary inode list, queueing the writes as we go. Then we clean
|
|
* up, waiting for those writes to complete.
|
|
*
|
|
* During this second stage, any subsequent updates to the file may end
|
|
* up refiling the buffer on the original inode's dirty list again, so
|
|
* there is a chance we will end up with a buffer queued for write but
|
|
* not yet completed on that list. So, as a final cleanup we go through
|
|
* the osync code to catch these locked, dirty buffers without requeuing
|
|
* any newly dirty buffers for write.
|
|
*/
|
|
static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
|
|
{
|
|
struct buffer_head *bh;
|
|
struct list_head tmp;
|
|
struct address_space *mapping;
|
|
int err = 0, err2;
|
|
struct blk_plug plug;
|
|
|
|
INIT_LIST_HEAD(&tmp);
|
|
blk_start_plug(&plug);
|
|
|
|
spin_lock(lock);
|
|
while (!list_empty(list)) {
|
|
bh = BH_ENTRY(list->next);
|
|
mapping = bh->b_assoc_map;
|
|
__remove_assoc_queue(bh);
|
|
/* Avoid race with mark_buffer_dirty_inode() which does
|
|
* a lockless check and we rely on seeing the dirty bit */
|
|
smp_mb();
|
|
if (buffer_dirty(bh) || buffer_locked(bh)) {
|
|
list_add(&bh->b_assoc_buffers, &tmp);
|
|
bh->b_assoc_map = mapping;
|
|
if (buffer_dirty(bh)) {
|
|
get_bh(bh);
|
|
spin_unlock(lock);
|
|
/*
|
|
* Ensure any pending I/O completes so that
|
|
* write_dirty_buffer() actually writes the
|
|
* current contents - it is a noop if I/O is
|
|
* still in flight on potentially older
|
|
* contents.
|
|
*/
|
|
write_dirty_buffer(bh, WRITE_SYNC);
|
|
|
|
/*
|
|
* Kick off IO for the previous mapping. Note
|
|
* that we will not run the very last mapping,
|
|
* wait_on_buffer() will do that for us
|
|
* through sync_buffer().
|
|
*/
|
|
brelse(bh);
|
|
spin_lock(lock);
|
|
}
|
|
}
|
|
}
|
|
|
|
spin_unlock(lock);
|
|
blk_finish_plug(&plug);
|
|
spin_lock(lock);
|
|
|
|
while (!list_empty(&tmp)) {
|
|
bh = BH_ENTRY(tmp.prev);
|
|
get_bh(bh);
|
|
mapping = bh->b_assoc_map;
|
|
__remove_assoc_queue(bh);
|
|
/* Avoid race with mark_buffer_dirty_inode() which does
|
|
* a lockless check and we rely on seeing the dirty bit */
|
|
smp_mb();
|
|
if (buffer_dirty(bh)) {
|
|
list_add(&bh->b_assoc_buffers,
|
|
&mapping->private_list);
|
|
bh->b_assoc_map = mapping;
|
|
}
|
|
spin_unlock(lock);
|
|
wait_on_buffer(bh);
|
|
if (!buffer_uptodate(bh))
|
|
err = -EIO;
|
|
brelse(bh);
|
|
spin_lock(lock);
|
|
}
|
|
|
|
spin_unlock(lock);
|
|
err2 = osync_buffers_list(lock, list);
|
|
if (err)
|
|
return err;
|
|
else
|
|
return err2;
|
|
}
|
|
|
|
/*
|
|
* Invalidate any and all dirty buffers on a given inode. We are
|
|
* probably unmounting the fs, but that doesn't mean we have already
|
|
* done a sync(). Just drop the buffers from the inode list.
|
|
*
|
|
* NOTE: we take the inode's blockdev's mapping's private_lock. Which
|
|
* assumes that all the buffers are against the blockdev. Not true
|
|
* for reiserfs.
|
|
*/
|
|
void invalidate_inode_buffers(struct inode *inode)
|
|
{
|
|
if (inode_has_buffers(inode)) {
|
|
struct address_space *mapping = &inode->i_data;
|
|
struct list_head *list = &mapping->private_list;
|
|
struct address_space *buffer_mapping = mapping->assoc_mapping;
|
|
|
|
spin_lock(&buffer_mapping->private_lock);
|
|
while (!list_empty(list))
|
|
__remove_assoc_queue(BH_ENTRY(list->next));
|
|
spin_unlock(&buffer_mapping->private_lock);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(invalidate_inode_buffers);
|
|
|
|
/*
|
|
* Remove any clean buffers from the inode's buffer list. This is called
|
|
* when we're trying to free the inode itself. Those buffers can pin it.
|
|
*
|
|
* Returns true if all buffers were removed.
|
|
*/
|
|
int remove_inode_buffers(struct inode *inode)
|
|
{
|
|
int ret = 1;
|
|
|
|
if (inode_has_buffers(inode)) {
|
|
struct address_space *mapping = &inode->i_data;
|
|
struct list_head *list = &mapping->private_list;
|
|
struct address_space *buffer_mapping = mapping->assoc_mapping;
|
|
|
|
spin_lock(&buffer_mapping->private_lock);
|
|
while (!list_empty(list)) {
|
|
struct buffer_head *bh = BH_ENTRY(list->next);
|
|
if (buffer_dirty(bh)) {
|
|
ret = 0;
|
|
break;
|
|
}
|
|
__remove_assoc_queue(bh);
|
|
}
|
|
spin_unlock(&buffer_mapping->private_lock);
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Create the appropriate buffers when given a page for data area and
|
|
* the size of each buffer.. Use the bh->b_this_page linked list to
|
|
* follow the buffers created. Return NULL if unable to create more
|
|
* buffers.
|
|
*
|
|
* The retry flag is used to differentiate async IO (paging, swapping)
|
|
* which may not fail from ordinary buffer allocations.
|
|
*/
|
|
struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
|
|
int retry)
|
|
{
|
|
struct buffer_head *bh, *head;
|
|
long offset;
|
|
|
|
try_again:
|
|
head = NULL;
|
|
offset = PAGE_SIZE;
|
|
while ((offset -= size) >= 0) {
|
|
bh = alloc_buffer_head(GFP_NOFS);
|
|
if (!bh)
|
|
goto no_grow;
|
|
|
|
bh->b_bdev = NULL;
|
|
bh->b_this_page = head;
|
|
bh->b_blocknr = -1;
|
|
head = bh;
|
|
|
|
bh->b_state = 0;
|
|
atomic_set(&bh->b_count, 0);
|
|
bh->b_size = size;
|
|
|
|
/* Link the buffer to its page */
|
|
set_bh_page(bh, page, offset);
|
|
|
|
init_buffer(bh, NULL, NULL);
|
|
}
|
|
return head;
|
|
/*
|
|
* In case anything failed, we just free everything we got.
|
|
*/
|
|
no_grow:
|
|
if (head) {
|
|
do {
|
|
bh = head;
|
|
head = head->b_this_page;
|
|
free_buffer_head(bh);
|
|
} while (head);
|
|
}
|
|
|
|
/*
|
|
* Return failure for non-async IO requests. Async IO requests
|
|
* are not allowed to fail, so we have to wait until buffer heads
|
|
* become available. But we don't want tasks sleeping with
|
|
* partially complete buffers, so all were released above.
|
|
*/
|
|
if (!retry)
|
|
return NULL;
|
|
|
|
/* We're _really_ low on memory. Now we just
|
|
* wait for old buffer heads to become free due to
|
|
* finishing IO. Since this is an async request and
|
|
* the reserve list is empty, we're sure there are
|
|
* async buffer heads in use.
|
|
*/
|
|
free_more_memory();
|
|
goto try_again;
|
|
}
|
|
EXPORT_SYMBOL_GPL(alloc_page_buffers);
|
|
|
|
static inline void
|
|
link_dev_buffers(struct page *page, struct buffer_head *head)
|
|
{
|
|
struct buffer_head *bh, *tail;
|
|
|
|
bh = head;
|
|
do {
|
|
tail = bh;
|
|
bh = bh->b_this_page;
|
|
} while (bh);
|
|
tail->b_this_page = head;
|
|
attach_page_buffers(page, head);
|
|
}
|
|
|
|
/*
|
|
* Initialise the state of a blockdev page's buffers.
|
|
*/
|
|
static void
|
|
init_page_buffers(struct page *page, struct block_device *bdev,
|
|
sector_t block, int size)
|
|
{
|
|
struct buffer_head *head = page_buffers(page);
|
|
struct buffer_head *bh = head;
|
|
int uptodate = PageUptodate(page);
|
|
|
|
do {
|
|
if (!buffer_mapped(bh)) {
|
|
init_buffer(bh, NULL, NULL);
|
|
bh->b_bdev = bdev;
|
|
bh->b_blocknr = block;
|
|
if (uptodate)
|
|
set_buffer_uptodate(bh);
|
|
set_buffer_mapped(bh);
|
|
}
|
|
block++;
|
|
bh = bh->b_this_page;
|
|
} while (bh != head);
|
|
}
|
|
|
|
/*
|
|
* Create the page-cache page that contains the requested block.
|
|
*
|
|
* This is user purely for blockdev mappings.
|
|
*/
|
|
static struct page *
|
|
grow_dev_page(struct block_device *bdev, sector_t block,
|
|
pgoff_t index, int size)
|
|
{
|
|
struct inode *inode = bdev->bd_inode;
|
|
struct page *page;
|
|
struct buffer_head *bh;
|
|
|
|
page = find_or_create_page(inode->i_mapping, index,
|
|
(mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
|
|
if (!page)
|
|
return NULL;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
|
|
if (page_has_buffers(page)) {
|
|
bh = page_buffers(page);
|
|
if (bh->b_size == size) {
|
|
init_page_buffers(page, bdev, block, size);
|
|
return page;
|
|
}
|
|
if (!try_to_free_buffers(page))
|
|
goto failed;
|
|
}
|
|
|
|
/*
|
|
* Allocate some buffers for this page
|
|
*/
|
|
bh = alloc_page_buffers(page, size, 0);
|
|
if (!bh)
|
|
goto failed;
|
|
|
|
/*
|
|
* Link the page to the buffers and initialise them. Take the
|
|
* lock to be atomic wrt __find_get_block(), which does not
|
|
* run under the page lock.
|
|
*/
|
|
spin_lock(&inode->i_mapping->private_lock);
|
|
link_dev_buffers(page, bh);
|
|
init_page_buffers(page, bdev, block, size);
|
|
spin_unlock(&inode->i_mapping->private_lock);
|
|
return page;
|
|
|
|
failed:
|
|
BUG();
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* Create buffers for the specified block device block's page. If
|
|
* that page was dirty, the buffers are set dirty also.
|
|
*/
|
|
static int
|
|
grow_buffers(struct block_device *bdev, sector_t block, int size)
|
|
{
|
|
struct page *page;
|
|
pgoff_t index;
|
|
int sizebits;
|
|
|
|
sizebits = -1;
|
|
do {
|
|
sizebits++;
|
|
} while ((size << sizebits) < PAGE_SIZE);
|
|
|
|
index = block >> sizebits;
|
|
|
|
/*
|
|
* Check for a block which wants to lie outside our maximum possible
|
|
* pagecache index. (this comparison is done using sector_t types).
|
|
*/
|
|
if (unlikely(index != block >> sizebits)) {
|
|
char b[BDEVNAME_SIZE];
|
|
|
|
printk(KERN_ERR "%s: requested out-of-range block %llu for "
|
|
"device %s\n",
|
|
__func__, (unsigned long long)block,
|
|
bdevname(bdev, b));
|
|
return -EIO;
|
|
}
|
|
block = index << sizebits;
|
|
/* Create a page with the proper size buffers.. */
|
|
page = grow_dev_page(bdev, block, index, size);
|
|
if (!page)
|
|
return 0;
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
return 1;
|
|
}
|
|
|
|
static struct buffer_head *
|
|
__getblk_slow(struct block_device *bdev, sector_t block, int size)
|
|
{
|
|
/* Size must be multiple of hard sectorsize */
|
|
if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
|
|
(size < 512 || size > PAGE_SIZE))) {
|
|
printk(KERN_ERR "getblk(): invalid block size %d requested\n",
|
|
size);
|
|
printk(KERN_ERR "logical block size: %d\n",
|
|
bdev_logical_block_size(bdev));
|
|
|
|
dump_stack();
|
|
return NULL;
|
|
}
|
|
|
|
for (;;) {
|
|
struct buffer_head * bh;
|
|
int ret;
|
|
|
|
bh = __find_get_block(bdev, block, size);
|
|
if (bh)
|
|
return bh;
|
|
|
|
ret = grow_buffers(bdev, block, size);
|
|
if (ret < 0)
|
|
return NULL;
|
|
if (ret == 0)
|
|
free_more_memory();
|
|
}
|
|
}
|
|
|
|
/*
|
|
* The relationship between dirty buffers and dirty pages:
|
|
*
|
|
* Whenever a page has any dirty buffers, the page's dirty bit is set, and
|
|
* the page is tagged dirty in its radix tree.
|
|
*
|
|
* At all times, the dirtiness of the buffers represents the dirtiness of
|
|
* subsections of the page. If the page has buffers, the page dirty bit is
|
|
* merely a hint about the true dirty state.
|
|
*
|
|
* When a page is set dirty in its entirety, all its buffers are marked dirty
|
|
* (if the page has buffers).
|
|
*
|
|
* When a buffer is marked dirty, its page is dirtied, but the page's other
|
|
* buffers are not.
|
|
*
|
|
* Also. When blockdev buffers are explicitly read with bread(), they
|
|
* individually become uptodate. But their backing page remains not
|
|
* uptodate - even if all of its buffers are uptodate. A subsequent
|
|
* block_read_full_page() against that page will discover all the uptodate
|
|
* buffers, will set the page uptodate and will perform no I/O.
|
|
*/
|
|
|
|
/**
|
|
* mark_buffer_dirty - mark a buffer_head as needing writeout
|
|
* @bh: the buffer_head to mark dirty
|
|
*
|
|
* mark_buffer_dirty() will set the dirty bit against the buffer, then set its
|
|
* backing page dirty, then tag the page as dirty in its address_space's radix
|
|
* tree and then attach the address_space's inode to its superblock's dirty
|
|
* inode list.
|
|
*
|
|
* mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
|
|
* mapping->tree_lock and mapping->host->i_lock.
|
|
*/
|
|
void mark_buffer_dirty(struct buffer_head *bh)
|
|
{
|
|
WARN_ON_ONCE(!buffer_uptodate(bh));
|
|
|
|
/*
|
|
* Very *carefully* optimize the it-is-already-dirty case.
|
|
*
|
|
* Don't let the final "is it dirty" escape to before we
|
|
* perhaps modified the buffer.
|
|
*/
|
|
if (buffer_dirty(bh)) {
|
|
smp_mb();
|
|
if (buffer_dirty(bh))
|
|
return;
|
|
}
|
|
|
|
if (!test_set_buffer_dirty(bh)) {
|
|
struct page *page = bh->b_page;
|
|
if (!TestSetPageDirty(page)) {
|
|
struct address_space *mapping = page_mapping(page);
|
|
if (mapping)
|
|
__set_page_dirty(page, mapping, 0);
|
|
}
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(mark_buffer_dirty);
|
|
|
|
/*
|
|
* Decrement a buffer_head's reference count. If all buffers against a page
|
|
* have zero reference count, are clean and unlocked, and if the page is clean
|
|
* and unlocked then try_to_free_buffers() may strip the buffers from the page
|
|
* in preparation for freeing it (sometimes, rarely, buffers are removed from
|
|
* a page but it ends up not being freed, and buffers may later be reattached).
|
|
*/
|
|
void __brelse(struct buffer_head * buf)
|
|
{
|
|
if (atomic_read(&buf->b_count)) {
|
|
put_bh(buf);
|
|
return;
|
|
}
|
|
WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
|
|
}
|
|
EXPORT_SYMBOL(__brelse);
|
|
|
|
/*
|
|
* bforget() is like brelse(), except it discards any
|
|
* potentially dirty data.
|
|
*/
|
|
void __bforget(struct buffer_head *bh)
|
|
{
|
|
clear_buffer_dirty(bh);
|
|
if (bh->b_assoc_map) {
|
|
struct address_space *buffer_mapping = bh->b_page->mapping;
|
|
|
|
spin_lock(&buffer_mapping->private_lock);
|
|
list_del_init(&bh->b_assoc_buffers);
|
|
bh->b_assoc_map = NULL;
|
|
spin_unlock(&buffer_mapping->private_lock);
|
|
}
|
|
__brelse(bh);
|
|
}
|
|
EXPORT_SYMBOL(__bforget);
|
|
|
|
static struct buffer_head *__bread_slow(struct buffer_head *bh)
|
|
{
|
|
lock_buffer(bh);
|
|
if (buffer_uptodate(bh)) {
|
|
unlock_buffer(bh);
|
|
return bh;
|
|
} else {
|
|
get_bh(bh);
|
|
bh->b_end_io = end_buffer_read_sync;
|
|
submit_bh(READ, bh);
|
|
wait_on_buffer(bh);
|
|
if (buffer_uptodate(bh))
|
|
return bh;
|
|
}
|
|
brelse(bh);
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
|
|
* The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
|
|
* refcount elevated by one when they're in an LRU. A buffer can only appear
|
|
* once in a particular CPU's LRU. A single buffer can be present in multiple
|
|
* CPU's LRUs at the same time.
|
|
*
|
|
* This is a transparent caching front-end to sb_bread(), sb_getblk() and
|
|
* sb_find_get_block().
|
|
*
|
|
* The LRUs themselves only need locking against invalidate_bh_lrus. We use
|
|
* a local interrupt disable for that.
|
|
*/
|
|
|
|
#define BH_LRU_SIZE 8
|
|
|
|
struct bh_lru {
|
|
struct buffer_head *bhs[BH_LRU_SIZE];
|
|
};
|
|
|
|
static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
|
|
|
|
#ifdef CONFIG_SMP
|
|
#define bh_lru_lock() local_irq_disable()
|
|
#define bh_lru_unlock() local_irq_enable()
|
|
#else
|
|
#define bh_lru_lock() preempt_disable()
|
|
#define bh_lru_unlock() preempt_enable()
|
|
#endif
|
|
|
|
static inline void check_irqs_on(void)
|
|
{
|
|
#ifdef irqs_disabled
|
|
BUG_ON(irqs_disabled());
|
|
#endif
|
|
}
|
|
|
|
/*
|
|
* The LRU management algorithm is dopey-but-simple. Sorry.
|
|
*/
|
|
static void bh_lru_install(struct buffer_head *bh)
|
|
{
|
|
struct buffer_head *evictee = NULL;
|
|
|
|
check_irqs_on();
|
|
bh_lru_lock();
|
|
if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
|
|
struct buffer_head *bhs[BH_LRU_SIZE];
|
|
int in;
|
|
int out = 0;
|
|
|
|
get_bh(bh);
|
|
bhs[out++] = bh;
|
|
for (in = 0; in < BH_LRU_SIZE; in++) {
|
|
struct buffer_head *bh2 =
|
|
__this_cpu_read(bh_lrus.bhs[in]);
|
|
|
|
if (bh2 == bh) {
|
|
__brelse(bh2);
|
|
} else {
|
|
if (out >= BH_LRU_SIZE) {
|
|
BUG_ON(evictee != NULL);
|
|
evictee = bh2;
|
|
} else {
|
|
bhs[out++] = bh2;
|
|
}
|
|
}
|
|
}
|
|
while (out < BH_LRU_SIZE)
|
|
bhs[out++] = NULL;
|
|
memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
|
|
}
|
|
bh_lru_unlock();
|
|
|
|
if (evictee)
|
|
__brelse(evictee);
|
|
}
|
|
|
|
/*
|
|
* Look up the bh in this cpu's LRU. If it's there, move it to the head.
|
|
*/
|
|
static struct buffer_head *
|
|
lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
|
|
{
|
|
struct buffer_head *ret = NULL;
|
|
unsigned int i;
|
|
|
|
check_irqs_on();
|
|
bh_lru_lock();
|
|
for (i = 0; i < BH_LRU_SIZE; i++) {
|
|
struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
|
|
|
|
if (bh && bh->b_bdev == bdev &&
|
|
bh->b_blocknr == block && bh->b_size == size) {
|
|
if (i) {
|
|
while (i) {
|
|
__this_cpu_write(bh_lrus.bhs[i],
|
|
__this_cpu_read(bh_lrus.bhs[i - 1]));
|
|
i--;
|
|
}
|
|
__this_cpu_write(bh_lrus.bhs[0], bh);
|
|
}
|
|
get_bh(bh);
|
|
ret = bh;
|
|
break;
|
|
}
|
|
}
|
|
bh_lru_unlock();
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Perform a pagecache lookup for the matching buffer. If it's there, refresh
|
|
* it in the LRU and mark it as accessed. If it is not present then return
|
|
* NULL
|
|
*/
|
|
struct buffer_head *
|
|
__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
|
|
{
|
|
struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
|
|
|
|
if (bh == NULL) {
|
|
bh = __find_get_block_slow(bdev, block);
|
|
if (bh)
|
|
bh_lru_install(bh);
|
|
}
|
|
if (bh)
|
|
touch_buffer(bh);
|
|
return bh;
|
|
}
|
|
EXPORT_SYMBOL(__find_get_block);
|
|
|
|
/*
|
|
* __getblk will locate (and, if necessary, create) the buffer_head
|
|
* which corresponds to the passed block_device, block and size. The
|
|
* returned buffer has its reference count incremented.
|
|
*
|
|
* __getblk() cannot fail - it just keeps trying. If you pass it an
|
|
* illegal block number, __getblk() will happily return a buffer_head
|
|
* which represents the non-existent block. Very weird.
|
|
*
|
|
* __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
|
|
* attempt is failing. FIXME, perhaps?
|
|
*/
|
|
struct buffer_head *
|
|
__getblk(struct block_device *bdev, sector_t block, unsigned size)
|
|
{
|
|
struct buffer_head *bh = __find_get_block(bdev, block, size);
|
|
|
|
might_sleep();
|
|
if (bh == NULL)
|
|
bh = __getblk_slow(bdev, block, size);
|
|
return bh;
|
|
}
|
|
EXPORT_SYMBOL(__getblk);
|
|
|
|
/*
|
|
* Do async read-ahead on a buffer..
|
|
*/
|
|
void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
|
|
{
|
|
struct buffer_head *bh = __getblk(bdev, block, size);
|
|
if (likely(bh)) {
|
|
ll_rw_block(READA, 1, &bh);
|
|
brelse(bh);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(__breadahead);
|
|
|
|
/**
|
|
* __bread() - reads a specified block and returns the bh
|
|
* @bdev: the block_device to read from
|
|
* @block: number of block
|
|
* @size: size (in bytes) to read
|
|
*
|
|
* Reads a specified block, and returns buffer head that contains it.
|
|
* It returns NULL if the block was unreadable.
|
|
*/
|
|
struct buffer_head *
|
|
__bread(struct block_device *bdev, sector_t block, unsigned size)
|
|
{
|
|
struct buffer_head *bh = __getblk(bdev, block, size);
|
|
|
|
if (likely(bh) && !buffer_uptodate(bh))
|
|
bh = __bread_slow(bh);
|
|
return bh;
|
|
}
|
|
EXPORT_SYMBOL(__bread);
|
|
|
|
/*
|
|
* invalidate_bh_lrus() is called rarely - but not only at unmount.
|
|
* This doesn't race because it runs in each cpu either in irq
|
|
* or with preempt disabled.
|
|
*/
|
|
static void invalidate_bh_lru(void *arg)
|
|
{
|
|
struct bh_lru *b = &get_cpu_var(bh_lrus);
|
|
int i;
|
|
|
|
for (i = 0; i < BH_LRU_SIZE; i++) {
|
|
brelse(b->bhs[i]);
|
|
b->bhs[i] = NULL;
|
|
}
|
|
put_cpu_var(bh_lrus);
|
|
}
|
|
|
|
void invalidate_bh_lrus(void)
|
|
{
|
|
on_each_cpu(invalidate_bh_lru, NULL, 1);
|
|
}
|
|
EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
|
|
|
|
void set_bh_page(struct buffer_head *bh,
|
|
struct page *page, unsigned long offset)
|
|
{
|
|
bh->b_page = page;
|
|
BUG_ON(offset >= PAGE_SIZE);
|
|
if (PageHighMem(page))
|
|
/*
|
|
* This catches illegal uses and preserves the offset:
|
|
*/
|
|
bh->b_data = (char *)(0 + offset);
|
|
else
|
|
bh->b_data = page_address(page) + offset;
|
|
}
|
|
EXPORT_SYMBOL(set_bh_page);
|
|
|
|
/*
|
|
* Called when truncating a buffer on a page completely.
|
|
*/
|
|
static void discard_buffer(struct buffer_head * bh)
|
|
{
|
|
lock_buffer(bh);
|
|
clear_buffer_dirty(bh);
|
|
bh->b_bdev = NULL;
|
|
clear_buffer_mapped(bh);
|
|
clear_buffer_req(bh);
|
|
clear_buffer_new(bh);
|
|
clear_buffer_delay(bh);
|
|
clear_buffer_unwritten(bh);
|
|
unlock_buffer(bh);
|
|
}
|
|
|
|
/**
|
|
* block_invalidatepage - invalidate part of all of a buffer-backed page
|
|
*
|
|
* @page: the page which is affected
|
|
* @offset: the index of the truncation point
|
|
*
|
|
* block_invalidatepage() is called when all or part of the page has become
|
|
* invalidatedby a truncate operation.
|
|
*
|
|
* block_invalidatepage() does not have to release all buffers, but it must
|
|
* ensure that no dirty buffer is left outside @offset and that no I/O
|
|
* is underway against any of the blocks which are outside the truncation
|
|
* point. Because the caller is about to free (and possibly reuse) those
|
|
* blocks on-disk.
|
|
*/
|
|
void block_invalidatepage(struct page *page, unsigned long offset)
|
|
{
|
|
struct buffer_head *head, *bh, *next;
|
|
unsigned int curr_off = 0;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
if (!page_has_buffers(page))
|
|
goto out;
|
|
|
|
head = page_buffers(page);
|
|
bh = head;
|
|
do {
|
|
unsigned int next_off = curr_off + bh->b_size;
|
|
next = bh->b_this_page;
|
|
|
|
/*
|
|
* is this block fully invalidated?
|
|
*/
|
|
if (offset <= curr_off)
|
|
discard_buffer(bh);
|
|
curr_off = next_off;
|
|
bh = next;
|
|
} while (bh != head);
|
|
|
|
/*
|
|
* We release buffers only if the entire page is being invalidated.
|
|
* The get_block cached value has been unconditionally invalidated,
|
|
* so real IO is not possible anymore.
|
|
*/
|
|
if (offset == 0)
|
|
try_to_release_page(page, 0);
|
|
out:
|
|
return;
|
|
}
|
|
EXPORT_SYMBOL(block_invalidatepage);
|
|
|
|
/*
|
|
* We attach and possibly dirty the buffers atomically wrt
|
|
* __set_page_dirty_buffers() via private_lock. try_to_free_buffers
|
|
* is already excluded via the page lock.
|
|
*/
|
|
void create_empty_buffers(struct page *page,
|
|
unsigned long blocksize, unsigned long b_state)
|
|
{
|
|
struct buffer_head *bh, *head, *tail;
|
|
|
|
head = alloc_page_buffers(page, blocksize, 1);
|
|
bh = head;
|
|
do {
|
|
bh->b_state |= b_state;
|
|
tail = bh;
|
|
bh = bh->b_this_page;
|
|
} while (bh);
|
|
tail->b_this_page = head;
|
|
|
|
spin_lock(&page->mapping->private_lock);
|
|
if (PageUptodate(page) || PageDirty(page)) {
|
|
bh = head;
|
|
do {
|
|
if (PageDirty(page))
|
|
set_buffer_dirty(bh);
|
|
if (PageUptodate(page))
|
|
set_buffer_uptodate(bh);
|
|
bh = bh->b_this_page;
|
|
} while (bh != head);
|
|
}
|
|
attach_page_buffers(page, head);
|
|
spin_unlock(&page->mapping->private_lock);
|
|
}
|
|
EXPORT_SYMBOL(create_empty_buffers);
|
|
|
|
/*
|
|
* We are taking a block for data and we don't want any output from any
|
|
* buffer-cache aliases starting from return from that function and
|
|
* until the moment when something will explicitly mark the buffer
|
|
* dirty (hopefully that will not happen until we will free that block ;-)
|
|
* We don't even need to mark it not-uptodate - nobody can expect
|
|
* anything from a newly allocated buffer anyway. We used to used
|
|
* unmap_buffer() for such invalidation, but that was wrong. We definitely
|
|
* don't want to mark the alias unmapped, for example - it would confuse
|
|
* anyone who might pick it with bread() afterwards...
|
|
*
|
|
* Also.. Note that bforget() doesn't lock the buffer. So there can
|
|
* be writeout I/O going on against recently-freed buffers. We don't
|
|
* wait on that I/O in bforget() - it's more efficient to wait on the I/O
|
|
* only if we really need to. That happens here.
|
|
*/
|
|
void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
|
|
{
|
|
struct buffer_head *old_bh;
|
|
|
|
might_sleep();
|
|
|
|
old_bh = __find_get_block_slow(bdev, block);
|
|
if (old_bh) {
|
|
clear_buffer_dirty(old_bh);
|
|
wait_on_buffer(old_bh);
|
|
clear_buffer_req(old_bh);
|
|
__brelse(old_bh);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(unmap_underlying_metadata);
|
|
|
|
/*
|
|
* NOTE! All mapped/uptodate combinations are valid:
|
|
*
|
|
* Mapped Uptodate Meaning
|
|
*
|
|
* No No "unknown" - must do get_block()
|
|
* No Yes "hole" - zero-filled
|
|
* Yes No "allocated" - allocated on disk, not read in
|
|
* Yes Yes "valid" - allocated and up-to-date in memory.
|
|
*
|
|
* "Dirty" is valid only with the last case (mapped+uptodate).
|
|
*/
|
|
|
|
/*
|
|
* While block_write_full_page is writing back the dirty buffers under
|
|
* the page lock, whoever dirtied the buffers may decide to clean them
|
|
* again at any time. We handle that by only looking at the buffer
|
|
* state inside lock_buffer().
|
|
*
|
|
* If block_write_full_page() is called for regular writeback
|
|
* (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
|
|
* locked buffer. This only can happen if someone has written the buffer
|
|
* directly, with submit_bh(). At the address_space level PageWriteback
|
|
* prevents this contention from occurring.
|
|
*
|
|
* If block_write_full_page() is called with wbc->sync_mode ==
|
|
* WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
|
|
* causes the writes to be flagged as synchronous writes.
|
|
*/
|
|
static int __block_write_full_page(struct inode *inode, struct page *page,
|
|
get_block_t *get_block, struct writeback_control *wbc,
|
|
bh_end_io_t *handler)
|
|
{
|
|
int err;
|
|
sector_t block;
|
|
sector_t last_block;
|
|
struct buffer_head *bh, *head;
|
|
const unsigned blocksize = 1 << inode->i_blkbits;
|
|
int nr_underway = 0;
|
|
int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
|
|
WRITE_SYNC : WRITE);
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
|
|
last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
|
|
|
|
if (!page_has_buffers(page)) {
|
|
create_empty_buffers(page, blocksize,
|
|
(1 << BH_Dirty)|(1 << BH_Uptodate));
|
|
}
|
|
|
|
/*
|
|
* Be very careful. We have no exclusion from __set_page_dirty_buffers
|
|
* here, and the (potentially unmapped) buffers may become dirty at
|
|
* any time. If a buffer becomes dirty here after we've inspected it
|
|
* then we just miss that fact, and the page stays dirty.
|
|
*
|
|
* Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
|
|
* handle that here by just cleaning them.
|
|
*/
|
|
|
|
block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
|
|
head = page_buffers(page);
|
|
bh = head;
|
|
|
|
/*
|
|
* Get all the dirty buffers mapped to disk addresses and
|
|
* handle any aliases from the underlying blockdev's mapping.
|
|
*/
|
|
do {
|
|
if (block > last_block) {
|
|
/*
|
|
* mapped buffers outside i_size will occur, because
|
|
* this page can be outside i_size when there is a
|
|
* truncate in progress.
|
|
*/
|
|
/*
|
|
* The buffer was zeroed by block_write_full_page()
|
|
*/
|
|
clear_buffer_dirty(bh);
|
|
set_buffer_uptodate(bh);
|
|
} else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
|
|
buffer_dirty(bh)) {
|
|
WARN_ON(bh->b_size != blocksize);
|
|
err = get_block(inode, block, bh, 1);
|
|
if (err)
|
|
goto recover;
|
|
clear_buffer_delay(bh);
|
|
if (buffer_new(bh)) {
|
|
/* blockdev mappings never come here */
|
|
clear_buffer_new(bh);
|
|
unmap_underlying_metadata(bh->b_bdev,
|
|
bh->b_blocknr);
|
|
}
|
|
}
|
|
bh = bh->b_this_page;
|
|
block++;
|
|
} while (bh != head);
|
|
|
|
do {
|
|
if (!buffer_mapped(bh))
|
|
continue;
|
|
/*
|
|
* If it's a fully non-blocking write attempt and we cannot
|
|
* lock the buffer then redirty the page. Note that this can
|
|
* potentially cause a busy-wait loop from writeback threads
|
|
* and kswapd activity, but those code paths have their own
|
|
* higher-level throttling.
|
|
*/
|
|
if (wbc->sync_mode != WB_SYNC_NONE) {
|
|
lock_buffer(bh);
|
|
} else if (!trylock_buffer(bh)) {
|
|
redirty_page_for_writepage(wbc, page);
|
|
continue;
|
|
}
|
|
if (test_clear_buffer_dirty(bh)) {
|
|
mark_buffer_async_write_endio(bh, handler);
|
|
} else {
|
|
unlock_buffer(bh);
|
|
}
|
|
} while ((bh = bh->b_this_page) != head);
|
|
|
|
/*
|
|
* The page and its buffers are protected by PageWriteback(), so we can
|
|
* drop the bh refcounts early.
|
|
*/
|
|
BUG_ON(PageWriteback(page));
|
|
set_page_writeback(page);
|
|
|
|
do {
|
|
struct buffer_head *next = bh->b_this_page;
|
|
if (buffer_async_write(bh)) {
|
|
submit_bh(write_op, bh);
|
|
nr_underway++;
|
|
}
|
|
bh = next;
|
|
} while (bh != head);
|
|
unlock_page(page);
|
|
|
|
err = 0;
|
|
done:
|
|
if (nr_underway == 0) {
|
|
/*
|
|
* The page was marked dirty, but the buffers were
|
|
* clean. Someone wrote them back by hand with
|
|
* ll_rw_block/submit_bh. A rare case.
|
|
*/
|
|
end_page_writeback(page);
|
|
|
|
/*
|
|
* The page and buffer_heads can be released at any time from
|
|
* here on.
|
|
*/
|
|
}
|
|
return err;
|
|
|
|
recover:
|
|
/*
|
|
* ENOSPC, or some other error. We may already have added some
|
|
* blocks to the file, so we need to write these out to avoid
|
|
* exposing stale data.
|
|
* The page is currently locked and not marked for writeback
|
|
*/
|
|
bh = head;
|
|
/* Recovery: lock and submit the mapped buffers */
|
|
do {
|
|
if (buffer_mapped(bh) && buffer_dirty(bh) &&
|
|
!buffer_delay(bh)) {
|
|
lock_buffer(bh);
|
|
mark_buffer_async_write_endio(bh, handler);
|
|
} else {
|
|
/*
|
|
* The buffer may have been set dirty during
|
|
* attachment to a dirty page.
|
|
*/
|
|
clear_buffer_dirty(bh);
|
|
}
|
|
} while ((bh = bh->b_this_page) != head);
|
|
SetPageError(page);
|
|
BUG_ON(PageWriteback(page));
|
|
mapping_set_error(page->mapping, err);
|
|
set_page_writeback(page);
|
|
do {
|
|
struct buffer_head *next = bh->b_this_page;
|
|
if (buffer_async_write(bh)) {
|
|
clear_buffer_dirty(bh);
|
|
submit_bh(write_op, bh);
|
|
nr_underway++;
|
|
}
|
|
bh = next;
|
|
} while (bh != head);
|
|
unlock_page(page);
|
|
goto done;
|
|
}
|
|
|
|
/*
|
|
* If a page has any new buffers, zero them out here, and mark them uptodate
|
|
* and dirty so they'll be written out (in order to prevent uninitialised
|
|
* block data from leaking). And clear the new bit.
|
|
*/
|
|
void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
|
|
{
|
|
unsigned int block_start, block_end;
|
|
struct buffer_head *head, *bh;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
if (!page_has_buffers(page))
|
|
return;
|
|
|
|
bh = head = page_buffers(page);
|
|
block_start = 0;
|
|
do {
|
|
block_end = block_start + bh->b_size;
|
|
|
|
if (buffer_new(bh)) {
|
|
if (block_end > from && block_start < to) {
|
|
if (!PageUptodate(page)) {
|
|
unsigned start, size;
|
|
|
|
start = max(from, block_start);
|
|
size = min(to, block_end) - start;
|
|
|
|
zero_user(page, start, size);
|
|
set_buffer_uptodate(bh);
|
|
}
|
|
|
|
clear_buffer_new(bh);
|
|
mark_buffer_dirty(bh);
|
|
}
|
|
}
|
|
|
|
block_start = block_end;
|
|
bh = bh->b_this_page;
|
|
} while (bh != head);
|
|
}
|
|
EXPORT_SYMBOL(page_zero_new_buffers);
|
|
|
|
int __block_write_begin(struct page *page, loff_t pos, unsigned len,
|
|
get_block_t *get_block)
|
|
{
|
|
unsigned from = pos & (PAGE_CACHE_SIZE - 1);
|
|
unsigned to = from + len;
|
|
struct inode *inode = page->mapping->host;
|
|
unsigned block_start, block_end;
|
|
sector_t block;
|
|
int err = 0;
|
|
unsigned blocksize, bbits;
|
|
struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
BUG_ON(from > PAGE_CACHE_SIZE);
|
|
BUG_ON(to > PAGE_CACHE_SIZE);
|
|
BUG_ON(from > to);
|
|
|
|
blocksize = 1 << inode->i_blkbits;
|
|
if (!page_has_buffers(page))
|
|
create_empty_buffers(page, blocksize, 0);
|
|
head = page_buffers(page);
|
|
|
|
bbits = inode->i_blkbits;
|
|
block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
|
|
|
|
for(bh = head, block_start = 0; bh != head || !block_start;
|
|
block++, block_start=block_end, bh = bh->b_this_page) {
|
|
block_end = block_start + blocksize;
|
|
if (block_end <= from || block_start >= to) {
|
|
if (PageUptodate(page)) {
|
|
if (!buffer_uptodate(bh))
|
|
set_buffer_uptodate(bh);
|
|
}
|
|
continue;
|
|
}
|
|
if (buffer_new(bh))
|
|
clear_buffer_new(bh);
|
|
if (!buffer_mapped(bh)) {
|
|
WARN_ON(bh->b_size != blocksize);
|
|
err = get_block(inode, block, bh, 1);
|
|
if (err)
|
|
break;
|
|
if (buffer_new(bh)) {
|
|
unmap_underlying_metadata(bh->b_bdev,
|
|
bh->b_blocknr);
|
|
if (PageUptodate(page)) {
|
|
clear_buffer_new(bh);
|
|
set_buffer_uptodate(bh);
|
|
mark_buffer_dirty(bh);
|
|
continue;
|
|
}
|
|
if (block_end > to || block_start < from)
|
|
zero_user_segments(page,
|
|
to, block_end,
|
|
block_start, from);
|
|
continue;
|
|
}
|
|
}
|
|
if (PageUptodate(page)) {
|
|
if (!buffer_uptodate(bh))
|
|
set_buffer_uptodate(bh);
|
|
continue;
|
|
}
|
|
if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
|
|
!buffer_unwritten(bh) &&
|
|
(block_start < from || block_end > to)) {
|
|
ll_rw_block(READ, 1, &bh);
|
|
*wait_bh++=bh;
|
|
}
|
|
}
|
|
/*
|
|
* If we issued read requests - let them complete.
|
|
*/
|
|
while(wait_bh > wait) {
|
|
wait_on_buffer(*--wait_bh);
|
|
if (!buffer_uptodate(*wait_bh))
|
|
err = -EIO;
|
|
}
|
|
if (unlikely(err)) {
|
|
page_zero_new_buffers(page, from, to);
|
|
ClearPageUptodate(page);
|
|
}
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL(__block_write_begin);
|
|
|
|
static int __block_commit_write(struct inode *inode, struct page *page,
|
|
unsigned from, unsigned to)
|
|
{
|
|
unsigned block_start, block_end;
|
|
int partial = 0;
|
|
unsigned blocksize;
|
|
struct buffer_head *bh, *head;
|
|
|
|
blocksize = 1 << inode->i_blkbits;
|
|
|
|
for(bh = head = page_buffers(page), block_start = 0;
|
|
bh != head || !block_start;
|
|
block_start=block_end, bh = bh->b_this_page) {
|
|
block_end = block_start + blocksize;
|
|
if (block_end <= from || block_start >= to) {
|
|
if (!buffer_uptodate(bh))
|
|
partial = 1;
|
|
} else {
|
|
set_buffer_uptodate(bh);
|
|
mark_buffer_dirty(bh);
|
|
}
|
|
clear_buffer_new(bh);
|
|
}
|
|
|
|
/*
|
|
* If this is a partial write which happened to make all buffers
|
|
* uptodate then we can optimize away a bogus readpage() for
|
|
* the next read(). Here we 'discover' whether the page went
|
|
* uptodate as a result of this (potentially partial) write.
|
|
*/
|
|
if (!partial)
|
|
SetPageUptodate(page);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* block_write_begin takes care of the basic task of block allocation and
|
|
* bringing partial write blocks uptodate first.
|
|
*
|
|
* The filesystem needs to handle block truncation upon failure.
|
|
*/
|
|
int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
|
|
unsigned flags, struct page **pagep, get_block_t *get_block)
|
|
{
|
|
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
|
|
struct page *page;
|
|
int status;
|
|
|
|
page = grab_cache_page_write_begin(mapping, index, flags);
|
|
if (!page)
|
|
return -ENOMEM;
|
|
|
|
status = __block_write_begin(page, pos, len, get_block);
|
|
if (unlikely(status)) {
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
page = NULL;
|
|
}
|
|
|
|
*pagep = page;
|
|
return status;
|
|
}
|
|
EXPORT_SYMBOL(block_write_begin);
|
|
|
|
int block_write_end(struct file *file, struct address_space *mapping,
|
|
loff_t pos, unsigned len, unsigned copied,
|
|
struct page *page, void *fsdata)
|
|
{
|
|
struct inode *inode = mapping->host;
|
|
unsigned start;
|
|
|
|
start = pos & (PAGE_CACHE_SIZE - 1);
|
|
|
|
if (unlikely(copied < len)) {
|
|
/*
|
|
* The buffers that were written will now be uptodate, so we
|
|
* don't have to worry about a readpage reading them and
|
|
* overwriting a partial write. However if we have encountered
|
|
* a short write and only partially written into a buffer, it
|
|
* will not be marked uptodate, so a readpage might come in and
|
|
* destroy our partial write.
|
|
*
|
|
* Do the simplest thing, and just treat any short write to a
|
|
* non uptodate page as a zero-length write, and force the
|
|
* caller to redo the whole thing.
|
|
*/
|
|
if (!PageUptodate(page))
|
|
copied = 0;
|
|
|
|
page_zero_new_buffers(page, start+copied, start+len);
|
|
}
|
|
flush_dcache_page(page);
|
|
|
|
/* This could be a short (even 0-length) commit */
|
|
__block_commit_write(inode, page, start, start+copied);
|
|
|
|
return copied;
|
|
}
|
|
EXPORT_SYMBOL(block_write_end);
|
|
|
|
int generic_write_end(struct file *file, struct address_space *mapping,
|
|
loff_t pos, unsigned len, unsigned copied,
|
|
struct page *page, void *fsdata)
|
|
{
|
|
struct inode *inode = mapping->host;
|
|
int i_size_changed = 0;
|
|
|
|
copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
|
|
|
|
/*
|
|
* No need to use i_size_read() here, the i_size
|
|
* cannot change under us because we hold i_mutex.
|
|
*
|
|
* But it's important to update i_size while still holding page lock:
|
|
* page writeout could otherwise come in and zero beyond i_size.
|
|
*/
|
|
if (pos+copied > inode->i_size) {
|
|
i_size_write(inode, pos+copied);
|
|
i_size_changed = 1;
|
|
}
|
|
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
|
|
/*
|
|
* Don't mark the inode dirty under page lock. First, it unnecessarily
|
|
* makes the holding time of page lock longer. Second, it forces lock
|
|
* ordering of page lock and transaction start for journaling
|
|
* filesystems.
|
|
*/
|
|
if (i_size_changed)
|
|
mark_inode_dirty(inode);
|
|
|
|
return copied;
|
|
}
|
|
EXPORT_SYMBOL(generic_write_end);
|
|
|
|
/*
|
|
* block_is_partially_uptodate checks whether buffers within a page are
|
|
* uptodate or not.
|
|
*
|
|
* Returns true if all buffers which correspond to a file portion
|
|
* we want to read are uptodate.
|
|
*/
|
|
int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
|
|
unsigned long from)
|
|
{
|
|
struct inode *inode = page->mapping->host;
|
|
unsigned block_start, block_end, blocksize;
|
|
unsigned to;
|
|
struct buffer_head *bh, *head;
|
|
int ret = 1;
|
|
|
|
if (!page_has_buffers(page))
|
|
return 0;
|
|
|
|
blocksize = 1 << inode->i_blkbits;
|
|
to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
|
|
to = from + to;
|
|
if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
|
|
return 0;
|
|
|
|
head = page_buffers(page);
|
|
bh = head;
|
|
block_start = 0;
|
|
do {
|
|
block_end = block_start + blocksize;
|
|
if (block_end > from && block_start < to) {
|
|
if (!buffer_uptodate(bh)) {
|
|
ret = 0;
|
|
break;
|
|
}
|
|
if (block_end >= to)
|
|
break;
|
|
}
|
|
block_start = block_end;
|
|
bh = bh->b_this_page;
|
|
} while (bh != head);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(block_is_partially_uptodate);
|
|
|
|
/*
|
|
* Generic "read page" function for block devices that have the normal
|
|
* get_block functionality. This is most of the block device filesystems.
|
|
* Reads the page asynchronously --- the unlock_buffer() and
|
|
* set/clear_buffer_uptodate() functions propagate buffer state into the
|
|
* page struct once IO has completed.
|
|
*/
|
|
int block_read_full_page(struct page *page, get_block_t *get_block)
|
|
{
|
|
struct inode *inode = page->mapping->host;
|
|
sector_t iblock, lblock;
|
|
struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
|
|
unsigned int blocksize;
|
|
int nr, i;
|
|
int fully_mapped = 1;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
blocksize = 1 << inode->i_blkbits;
|
|
if (!page_has_buffers(page))
|
|
create_empty_buffers(page, blocksize, 0);
|
|
head = page_buffers(page);
|
|
|
|
iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
|
|
lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
|
|
bh = head;
|
|
nr = 0;
|
|
i = 0;
|
|
|
|
do {
|
|
if (buffer_uptodate(bh))
|
|
continue;
|
|
|
|
if (!buffer_mapped(bh)) {
|
|
int err = 0;
|
|
|
|
fully_mapped = 0;
|
|
if (iblock < lblock) {
|
|
WARN_ON(bh->b_size != blocksize);
|
|
err = get_block(inode, iblock, bh, 0);
|
|
if (err)
|
|
SetPageError(page);
|
|
}
|
|
if (!buffer_mapped(bh)) {
|
|
zero_user(page, i * blocksize, blocksize);
|
|
if (!err)
|
|
set_buffer_uptodate(bh);
|
|
continue;
|
|
}
|
|
/*
|
|
* get_block() might have updated the buffer
|
|
* synchronously
|
|
*/
|
|
if (buffer_uptodate(bh))
|
|
continue;
|
|
}
|
|
arr[nr++] = bh;
|
|
} while (i++, iblock++, (bh = bh->b_this_page) != head);
|
|
|
|
if (fully_mapped)
|
|
SetPageMappedToDisk(page);
|
|
|
|
if (!nr) {
|
|
/*
|
|
* All buffers are uptodate - we can set the page uptodate
|
|
* as well. But not if get_block() returned an error.
|
|
*/
|
|
if (!PageError(page))
|
|
SetPageUptodate(page);
|
|
unlock_page(page);
|
|
return 0;
|
|
}
|
|
|
|
/* Stage two: lock the buffers */
|
|
for (i = 0; i < nr; i++) {
|
|
bh = arr[i];
|
|
lock_buffer(bh);
|
|
mark_buffer_async_read(bh);
|
|
}
|
|
|
|
/*
|
|
* Stage 3: start the IO. Check for uptodateness
|
|
* inside the buffer lock in case another process reading
|
|
* the underlying blockdev brought it uptodate (the sct fix).
|
|
*/
|
|
for (i = 0; i < nr; i++) {
|
|
bh = arr[i];
|
|
if (buffer_uptodate(bh))
|
|
end_buffer_async_read(bh, 1);
|
|
else
|
|
submit_bh(READ, bh);
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(block_read_full_page);
|
|
|
|
/* utility function for filesystems that need to do work on expanding
|
|
* truncates. Uses filesystem pagecache writes to allow the filesystem to
|
|
* deal with the hole.
|
|
*/
|
|
int generic_cont_expand_simple(struct inode *inode, loff_t size)
|
|
{
|
|
struct address_space *mapping = inode->i_mapping;
|
|
struct page *page;
|
|
void *fsdata;
|
|
int err;
|
|
|
|
err = inode_newsize_ok(inode, size);
|
|
if (err)
|
|
goto out;
|
|
|
|
err = pagecache_write_begin(NULL, mapping, size, 0,
|
|
AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
|
|
&page, &fsdata);
|
|
if (err)
|
|
goto out;
|
|
|
|
err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
|
|
BUG_ON(err > 0);
|
|
|
|
out:
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL(generic_cont_expand_simple);
|
|
|
|
static int cont_expand_zero(struct file *file, struct address_space *mapping,
|
|
loff_t pos, loff_t *bytes)
|
|
{
|
|
struct inode *inode = mapping->host;
|
|
unsigned blocksize = 1 << inode->i_blkbits;
|
|
struct page *page;
|
|
void *fsdata;
|
|
pgoff_t index, curidx;
|
|
loff_t curpos;
|
|
unsigned zerofrom, offset, len;
|
|
int err = 0;
|
|
|
|
index = pos >> PAGE_CACHE_SHIFT;
|
|
offset = pos & ~PAGE_CACHE_MASK;
|
|
|
|
while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
|
|
zerofrom = curpos & ~PAGE_CACHE_MASK;
|
|
if (zerofrom & (blocksize-1)) {
|
|
*bytes |= (blocksize-1);
|
|
(*bytes)++;
|
|
}
|
|
len = PAGE_CACHE_SIZE - zerofrom;
|
|
|
|
err = pagecache_write_begin(file, mapping, curpos, len,
|
|
AOP_FLAG_UNINTERRUPTIBLE,
|
|
&page, &fsdata);
|
|
if (err)
|
|
goto out;
|
|
zero_user(page, zerofrom, len);
|
|
err = pagecache_write_end(file, mapping, curpos, len, len,
|
|
page, fsdata);
|
|
if (err < 0)
|
|
goto out;
|
|
BUG_ON(err != len);
|
|
err = 0;
|
|
|
|
balance_dirty_pages_ratelimited(mapping);
|
|
}
|
|
|
|
/* page covers the boundary, find the boundary offset */
|
|
if (index == curidx) {
|
|
zerofrom = curpos & ~PAGE_CACHE_MASK;
|
|
/* if we will expand the thing last block will be filled */
|
|
if (offset <= zerofrom) {
|
|
goto out;
|
|
}
|
|
if (zerofrom & (blocksize-1)) {
|
|
*bytes |= (blocksize-1);
|
|
(*bytes)++;
|
|
}
|
|
len = offset - zerofrom;
|
|
|
|
err = pagecache_write_begin(file, mapping, curpos, len,
|
|
AOP_FLAG_UNINTERRUPTIBLE,
|
|
&page, &fsdata);
|
|
if (err)
|
|
goto out;
|
|
zero_user(page, zerofrom, len);
|
|
err = pagecache_write_end(file, mapping, curpos, len, len,
|
|
page, fsdata);
|
|
if (err < 0)
|
|
goto out;
|
|
BUG_ON(err != len);
|
|
err = 0;
|
|
}
|
|
out:
|
|
return err;
|
|
}
|
|
|
|
/*
|
|
* For moronic filesystems that do not allow holes in file.
|
|
* We may have to extend the file.
|
|
*/
|
|
int cont_write_begin(struct file *file, struct address_space *mapping,
|
|
loff_t pos, unsigned len, unsigned flags,
|
|
struct page **pagep, void **fsdata,
|
|
get_block_t *get_block, loff_t *bytes)
|
|
{
|
|
struct inode *inode = mapping->host;
|
|
unsigned blocksize = 1 << inode->i_blkbits;
|
|
unsigned zerofrom;
|
|
int err;
|
|
|
|
err = cont_expand_zero(file, mapping, pos, bytes);
|
|
if (err)
|
|
return err;
|
|
|
|
zerofrom = *bytes & ~PAGE_CACHE_MASK;
|
|
if (pos+len > *bytes && zerofrom & (blocksize-1)) {
|
|
*bytes |= (blocksize-1);
|
|
(*bytes)++;
|
|
}
|
|
|
|
return block_write_begin(mapping, pos, len, flags, pagep, get_block);
|
|
}
|
|
EXPORT_SYMBOL(cont_write_begin);
|
|
|
|
int block_commit_write(struct page *page, unsigned from, unsigned to)
|
|
{
|
|
struct inode *inode = page->mapping->host;
|
|
__block_commit_write(inode,page,from,to);
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(block_commit_write);
|
|
|
|
/*
|
|
* block_page_mkwrite() is not allowed to change the file size as it gets
|
|
* called from a page fault handler when a page is first dirtied. Hence we must
|
|
* be careful to check for EOF conditions here. We set the page up correctly
|
|
* for a written page which means we get ENOSPC checking when writing into
|
|
* holes and correct delalloc and unwritten extent mapping on filesystems that
|
|
* support these features.
|
|
*
|
|
* We are not allowed to take the i_mutex here so we have to play games to
|
|
* protect against truncate races as the page could now be beyond EOF. Because
|
|
* truncate writes the inode size before removing pages, once we have the
|
|
* page lock we can determine safely if the page is beyond EOF. If it is not
|
|
* beyond EOF, then the page is guaranteed safe against truncation until we
|
|
* unlock the page.
|
|
*/
|
|
int
|
|
block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
|
|
get_block_t get_block)
|
|
{
|
|
struct page *page = vmf->page;
|
|
struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
|
|
unsigned long end;
|
|
loff_t size;
|
|
int ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */
|
|
|
|
lock_page(page);
|
|
size = i_size_read(inode);
|
|
if ((page->mapping != inode->i_mapping) ||
|
|
(page_offset(page) > size)) {
|
|
/* page got truncated out from underneath us */
|
|
unlock_page(page);
|
|
goto out;
|
|
}
|
|
|
|
/* page is wholly or partially inside EOF */
|
|
if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
|
|
end = size & ~PAGE_CACHE_MASK;
|
|
else
|
|
end = PAGE_CACHE_SIZE;
|
|
|
|
ret = __block_write_begin(page, 0, end, get_block);
|
|
if (!ret)
|
|
ret = block_commit_write(page, 0, end);
|
|
|
|
if (unlikely(ret)) {
|
|
unlock_page(page);
|
|
if (ret == -ENOMEM)
|
|
ret = VM_FAULT_OOM;
|
|
else /* -ENOSPC, -EIO, etc */
|
|
ret = VM_FAULT_SIGBUS;
|
|
} else
|
|
ret = VM_FAULT_LOCKED;
|
|
|
|
out:
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(block_page_mkwrite);
|
|
|
|
/*
|
|
* nobh_write_begin()'s prereads are special: the buffer_heads are freed
|
|
* immediately, while under the page lock. So it needs a special end_io
|
|
* handler which does not touch the bh after unlocking it.
|
|
*/
|
|
static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
|
|
{
|
|
__end_buffer_read_notouch(bh, uptodate);
|
|
}
|
|
|
|
/*
|
|
* Attach the singly-linked list of buffers created by nobh_write_begin, to
|
|
* the page (converting it to circular linked list and taking care of page
|
|
* dirty races).
|
|
*/
|
|
static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
|
|
{
|
|
struct buffer_head *bh;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
|
|
spin_lock(&page->mapping->private_lock);
|
|
bh = head;
|
|
do {
|
|
if (PageDirty(page))
|
|
set_buffer_dirty(bh);
|
|
if (!bh->b_this_page)
|
|
bh->b_this_page = head;
|
|
bh = bh->b_this_page;
|
|
} while (bh != head);
|
|
attach_page_buffers(page, head);
|
|
spin_unlock(&page->mapping->private_lock);
|
|
}
|
|
|
|
/*
|
|
* On entry, the page is fully not uptodate.
|
|
* On exit the page is fully uptodate in the areas outside (from,to)
|
|
* The filesystem needs to handle block truncation upon failure.
|
|
*/
|
|
int nobh_write_begin(struct address_space *mapping,
|
|
loff_t pos, unsigned len, unsigned flags,
|
|
struct page **pagep, void **fsdata,
|
|
get_block_t *get_block)
|
|
{
|
|
struct inode *inode = mapping->host;
|
|
const unsigned blkbits = inode->i_blkbits;
|
|
const unsigned blocksize = 1 << blkbits;
|
|
struct buffer_head *head, *bh;
|
|
struct page *page;
|
|
pgoff_t index;
|
|
unsigned from, to;
|
|
unsigned block_in_page;
|
|
unsigned block_start, block_end;
|
|
sector_t block_in_file;
|
|
int nr_reads = 0;
|
|
int ret = 0;
|
|
int is_mapped_to_disk = 1;
|
|
|
|
index = pos >> PAGE_CACHE_SHIFT;
|
|
from = pos & (PAGE_CACHE_SIZE - 1);
|
|
to = from + len;
|
|
|
|
page = grab_cache_page_write_begin(mapping, index, flags);
|
|
if (!page)
|
|
return -ENOMEM;
|
|
*pagep = page;
|
|
*fsdata = NULL;
|
|
|
|
if (page_has_buffers(page)) {
|
|
ret = __block_write_begin(page, pos, len, get_block);
|
|
if (unlikely(ret))
|
|
goto out_release;
|
|
return ret;
|
|
}
|
|
|
|
if (PageMappedToDisk(page))
|
|
return 0;
|
|
|
|
/*
|
|
* Allocate buffers so that we can keep track of state, and potentially
|
|
* attach them to the page if an error occurs. In the common case of
|
|
* no error, they will just be freed again without ever being attached
|
|
* to the page (which is all OK, because we're under the page lock).
|
|
*
|
|
* Be careful: the buffer linked list is a NULL terminated one, rather
|
|
* than the circular one we're used to.
|
|
*/
|
|
head = alloc_page_buffers(page, blocksize, 0);
|
|
if (!head) {
|
|
ret = -ENOMEM;
|
|
goto out_release;
|
|
}
|
|
|
|
block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
|
|
|
|
/*
|
|
* We loop across all blocks in the page, whether or not they are
|
|
* part of the affected region. This is so we can discover if the
|
|
* page is fully mapped-to-disk.
|
|
*/
|
|
for (block_start = 0, block_in_page = 0, bh = head;
|
|
block_start < PAGE_CACHE_SIZE;
|
|
block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
|
|
int create;
|
|
|
|
block_end = block_start + blocksize;
|
|
bh->b_state = 0;
|
|
create = 1;
|
|
if (block_start >= to)
|
|
create = 0;
|
|
ret = get_block(inode, block_in_file + block_in_page,
|
|
bh, create);
|
|
if (ret)
|
|
goto failed;
|
|
if (!buffer_mapped(bh))
|
|
is_mapped_to_disk = 0;
|
|
if (buffer_new(bh))
|
|
unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
|
|
if (PageUptodate(page)) {
|
|
set_buffer_uptodate(bh);
|
|
continue;
|
|
}
|
|
if (buffer_new(bh) || !buffer_mapped(bh)) {
|
|
zero_user_segments(page, block_start, from,
|
|
to, block_end);
|
|
continue;
|
|
}
|
|
if (buffer_uptodate(bh))
|
|
continue; /* reiserfs does this */
|
|
if (block_start < from || block_end > to) {
|
|
lock_buffer(bh);
|
|
bh->b_end_io = end_buffer_read_nobh;
|
|
submit_bh(READ, bh);
|
|
nr_reads++;
|
|
}
|
|
}
|
|
|
|
if (nr_reads) {
|
|
/*
|
|
* The page is locked, so these buffers are protected from
|
|
* any VM or truncate activity. Hence we don't need to care
|
|
* for the buffer_head refcounts.
|
|
*/
|
|
for (bh = head; bh; bh = bh->b_this_page) {
|
|
wait_on_buffer(bh);
|
|
if (!buffer_uptodate(bh))
|
|
ret = -EIO;
|
|
}
|
|
if (ret)
|
|
goto failed;
|
|
}
|
|
|
|
if (is_mapped_to_disk)
|
|
SetPageMappedToDisk(page);
|
|
|
|
*fsdata = head; /* to be released by nobh_write_end */
|
|
|
|
return 0;
|
|
|
|
failed:
|
|
BUG_ON(!ret);
|
|
/*
|
|
* Error recovery is a bit difficult. We need to zero out blocks that
|
|
* were newly allocated, and dirty them to ensure they get written out.
|
|
* Buffers need to be attached to the page at this point, otherwise
|
|
* the handling of potential IO errors during writeout would be hard
|
|
* (could try doing synchronous writeout, but what if that fails too?)
|
|
*/
|
|
attach_nobh_buffers(page, head);
|
|
page_zero_new_buffers(page, from, to);
|
|
|
|
out_release:
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
*pagep = NULL;
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(nobh_write_begin);
|
|
|
|
int nobh_write_end(struct file *file, struct address_space *mapping,
|
|
loff_t pos, unsigned len, unsigned copied,
|
|
struct page *page, void *fsdata)
|
|
{
|
|
struct inode *inode = page->mapping->host;
|
|
struct buffer_head *head = fsdata;
|
|
struct buffer_head *bh;
|
|
BUG_ON(fsdata != NULL && page_has_buffers(page));
|
|
|
|
if (unlikely(copied < len) && head)
|
|
attach_nobh_buffers(page, head);
|
|
if (page_has_buffers(page))
|
|
return generic_write_end(file, mapping, pos, len,
|
|
copied, page, fsdata);
|
|
|
|
SetPageUptodate(page);
|
|
set_page_dirty(page);
|
|
if (pos+copied > inode->i_size) {
|
|
i_size_write(inode, pos+copied);
|
|
mark_inode_dirty(inode);
|
|
}
|
|
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
|
|
while (head) {
|
|
bh = head;
|
|
head = head->b_this_page;
|
|
free_buffer_head(bh);
|
|
}
|
|
|
|
return copied;
|
|
}
|
|
EXPORT_SYMBOL(nobh_write_end);
|
|
|
|
/*
|
|
* nobh_writepage() - based on block_full_write_page() except
|
|
* that it tries to operate without attaching bufferheads to
|
|
* the page.
|
|
*/
|
|
int nobh_writepage(struct page *page, get_block_t *get_block,
|
|
struct writeback_control *wbc)
|
|
{
|
|
struct inode * const inode = page->mapping->host;
|
|
loff_t i_size = i_size_read(inode);
|
|
const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
|
|
unsigned offset;
|
|
int ret;
|
|
|
|
/* Is the page fully inside i_size? */
|
|
if (page->index < end_index)
|
|
goto out;
|
|
|
|
/* Is the page fully outside i_size? (truncate in progress) */
|
|
offset = i_size & (PAGE_CACHE_SIZE-1);
|
|
if (page->index >= end_index+1 || !offset) {
|
|
/*
|
|
* The page may have dirty, unmapped buffers. For example,
|
|
* they may have been added in ext3_writepage(). Make them
|
|
* freeable here, so the page does not leak.
|
|
*/
|
|
#if 0
|
|
/* Not really sure about this - do we need this ? */
|
|
if (page->mapping->a_ops->invalidatepage)
|
|
page->mapping->a_ops->invalidatepage(page, offset);
|
|
#endif
|
|
unlock_page(page);
|
|
return 0; /* don't care */
|
|
}
|
|
|
|
/*
|
|
* The page straddles i_size. It must be zeroed out on each and every
|
|
* writepage invocation because it may be mmapped. "A file is mapped
|
|
* in multiples of the page size. For a file that is not a multiple of
|
|
* the page size, the remaining memory is zeroed when mapped, and
|
|
* writes to that region are not written out to the file."
|
|
*/
|
|
zero_user_segment(page, offset, PAGE_CACHE_SIZE);
|
|
out:
|
|
ret = mpage_writepage(page, get_block, wbc);
|
|
if (ret == -EAGAIN)
|
|
ret = __block_write_full_page(inode, page, get_block, wbc,
|
|
end_buffer_async_write);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(nobh_writepage);
|
|
|
|
int nobh_truncate_page(struct address_space *mapping,
|
|
loff_t from, get_block_t *get_block)
|
|
{
|
|
pgoff_t index = from >> PAGE_CACHE_SHIFT;
|
|
unsigned offset = from & (PAGE_CACHE_SIZE-1);
|
|
unsigned blocksize;
|
|
sector_t iblock;
|
|
unsigned length, pos;
|
|
struct inode *inode = mapping->host;
|
|
struct page *page;
|
|
struct buffer_head map_bh;
|
|
int err;
|
|
|
|
blocksize = 1 << inode->i_blkbits;
|
|
length = offset & (blocksize - 1);
|
|
|
|
/* Block boundary? Nothing to do */
|
|
if (!length)
|
|
return 0;
|
|
|
|
length = blocksize - length;
|
|
iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
|
|
|
|
page = grab_cache_page(mapping, index);
|
|
err = -ENOMEM;
|
|
if (!page)
|
|
goto out;
|
|
|
|
if (page_has_buffers(page)) {
|
|
has_buffers:
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
return block_truncate_page(mapping, from, get_block);
|
|
}
|
|
|
|
/* Find the buffer that contains "offset" */
|
|
pos = blocksize;
|
|
while (offset >= pos) {
|
|
iblock++;
|
|
pos += blocksize;
|
|
}
|
|
|
|
map_bh.b_size = blocksize;
|
|
map_bh.b_state = 0;
|
|
err = get_block(inode, iblock, &map_bh, 0);
|
|
if (err)
|
|
goto unlock;
|
|
/* unmapped? It's a hole - nothing to do */
|
|
if (!buffer_mapped(&map_bh))
|
|
goto unlock;
|
|
|
|
/* Ok, it's mapped. Make sure it's up-to-date */
|
|
if (!PageUptodate(page)) {
|
|
err = mapping->a_ops->readpage(NULL, page);
|
|
if (err) {
|
|
page_cache_release(page);
|
|
goto out;
|
|
}
|
|
lock_page(page);
|
|
if (!PageUptodate(page)) {
|
|
err = -EIO;
|
|
goto unlock;
|
|
}
|
|
if (page_has_buffers(page))
|
|
goto has_buffers;
|
|
}
|
|
zero_user(page, offset, length);
|
|
set_page_dirty(page);
|
|
err = 0;
|
|
|
|
unlock:
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
out:
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL(nobh_truncate_page);
|
|
|
|
int block_truncate_page(struct address_space *mapping,
|
|
loff_t from, get_block_t *get_block)
|
|
{
|
|
pgoff_t index = from >> PAGE_CACHE_SHIFT;
|
|
unsigned offset = from & (PAGE_CACHE_SIZE-1);
|
|
unsigned blocksize;
|
|
sector_t iblock;
|
|
unsigned length, pos;
|
|
struct inode *inode = mapping->host;
|
|
struct page *page;
|
|
struct buffer_head *bh;
|
|
int err;
|
|
|
|
blocksize = 1 << inode->i_blkbits;
|
|
length = offset & (blocksize - 1);
|
|
|
|
/* Block boundary? Nothing to do */
|
|
if (!length)
|
|
return 0;
|
|
|
|
length = blocksize - length;
|
|
iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
|
|
|
|
page = grab_cache_page(mapping, index);
|
|
err = -ENOMEM;
|
|
if (!page)
|
|
goto out;
|
|
|
|
if (!page_has_buffers(page))
|
|
create_empty_buffers(page, blocksize, 0);
|
|
|
|
/* Find the buffer that contains "offset" */
|
|
bh = page_buffers(page);
|
|
pos = blocksize;
|
|
while (offset >= pos) {
|
|
bh = bh->b_this_page;
|
|
iblock++;
|
|
pos += blocksize;
|
|
}
|
|
|
|
err = 0;
|
|
if (!buffer_mapped(bh)) {
|
|
WARN_ON(bh->b_size != blocksize);
|
|
err = get_block(inode, iblock, bh, 0);
|
|
if (err)
|
|
goto unlock;
|
|
/* unmapped? It's a hole - nothing to do */
|
|
if (!buffer_mapped(bh))
|
|
goto unlock;
|
|
}
|
|
|
|
/* Ok, it's mapped. Make sure it's up-to-date */
|
|
if (PageUptodate(page))
|
|
set_buffer_uptodate(bh);
|
|
|
|
if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
|
|
err = -EIO;
|
|
ll_rw_block(READ, 1, &bh);
|
|
wait_on_buffer(bh);
|
|
/* Uhhuh. Read error. Complain and punt. */
|
|
if (!buffer_uptodate(bh))
|
|
goto unlock;
|
|
}
|
|
|
|
zero_user(page, offset, length);
|
|
mark_buffer_dirty(bh);
|
|
err = 0;
|
|
|
|
unlock:
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
out:
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL(block_truncate_page);
|
|
|
|
/*
|
|
* The generic ->writepage function for buffer-backed address_spaces
|
|
* this form passes in the end_io handler used to finish the IO.
|
|
*/
|
|
int block_write_full_page_endio(struct page *page, get_block_t *get_block,
|
|
struct writeback_control *wbc, bh_end_io_t *handler)
|
|
{
|
|
struct inode * const inode = page->mapping->host;
|
|
loff_t i_size = i_size_read(inode);
|
|
const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
|
|
unsigned offset;
|
|
|
|
/* Is the page fully inside i_size? */
|
|
if (page->index < end_index)
|
|
return __block_write_full_page(inode, page, get_block, wbc,
|
|
handler);
|
|
|
|
/* Is the page fully outside i_size? (truncate in progress) */
|
|
offset = i_size & (PAGE_CACHE_SIZE-1);
|
|
if (page->index >= end_index+1 || !offset) {
|
|
/*
|
|
* The page may have dirty, unmapped buffers. For example,
|
|
* they may have been added in ext3_writepage(). Make them
|
|
* freeable here, so the page does not leak.
|
|
*/
|
|
do_invalidatepage(page, 0);
|
|
unlock_page(page);
|
|
return 0; /* don't care */
|
|
}
|
|
|
|
/*
|
|
* The page straddles i_size. It must be zeroed out on each and every
|
|
* writepage invocation because it may be mmapped. "A file is mapped
|
|
* in multiples of the page size. For a file that is not a multiple of
|
|
* the page size, the remaining memory is zeroed when mapped, and
|
|
* writes to that region are not written out to the file."
|
|
*/
|
|
zero_user_segment(page, offset, PAGE_CACHE_SIZE);
|
|
return __block_write_full_page(inode, page, get_block, wbc, handler);
|
|
}
|
|
EXPORT_SYMBOL(block_write_full_page_endio);
|
|
|
|
/*
|
|
* The generic ->writepage function for buffer-backed address_spaces
|
|
*/
|
|
int block_write_full_page(struct page *page, get_block_t *get_block,
|
|
struct writeback_control *wbc)
|
|
{
|
|
return block_write_full_page_endio(page, get_block, wbc,
|
|
end_buffer_async_write);
|
|
}
|
|
EXPORT_SYMBOL(block_write_full_page);
|
|
|
|
sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
|
|
get_block_t *get_block)
|
|
{
|
|
struct buffer_head tmp;
|
|
struct inode *inode = mapping->host;
|
|
tmp.b_state = 0;
|
|
tmp.b_blocknr = 0;
|
|
tmp.b_size = 1 << inode->i_blkbits;
|
|
get_block(inode, block, &tmp, 0);
|
|
return tmp.b_blocknr;
|
|
}
|
|
EXPORT_SYMBOL(generic_block_bmap);
|
|
|
|
static void end_bio_bh_io_sync(struct bio *bio, int err)
|
|
{
|
|
struct buffer_head *bh = bio->bi_private;
|
|
|
|
if (err == -EOPNOTSUPP) {
|
|
set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
|
|
}
|
|
|
|
if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
|
|
set_bit(BH_Quiet, &bh->b_state);
|
|
|
|
bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
|
|
bio_put(bio);
|
|
}
|
|
|
|
int submit_bh(int rw, struct buffer_head * bh)
|
|
{
|
|
struct bio *bio;
|
|
int ret = 0;
|
|
|
|
BUG_ON(!buffer_locked(bh));
|
|
BUG_ON(!buffer_mapped(bh));
|
|
BUG_ON(!bh->b_end_io);
|
|
BUG_ON(buffer_delay(bh));
|
|
BUG_ON(buffer_unwritten(bh));
|
|
|
|
/*
|
|
* Only clear out a write error when rewriting
|
|
*/
|
|
if (test_set_buffer_req(bh) && (rw & WRITE))
|
|
clear_buffer_write_io_error(bh);
|
|
|
|
/*
|
|
* from here on down, it's all bio -- do the initial mapping,
|
|
* submit_bio -> generic_make_request may further map this bio around
|
|
*/
|
|
bio = bio_alloc(GFP_NOIO, 1);
|
|
|
|
bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
|
|
bio->bi_bdev = bh->b_bdev;
|
|
bio->bi_io_vec[0].bv_page = bh->b_page;
|
|
bio->bi_io_vec[0].bv_len = bh->b_size;
|
|
bio->bi_io_vec[0].bv_offset = bh_offset(bh);
|
|
|
|
bio->bi_vcnt = 1;
|
|
bio->bi_idx = 0;
|
|
bio->bi_size = bh->b_size;
|
|
|
|
bio->bi_end_io = end_bio_bh_io_sync;
|
|
bio->bi_private = bh;
|
|
|
|
bio_get(bio);
|
|
submit_bio(rw, bio);
|
|
|
|
if (bio_flagged(bio, BIO_EOPNOTSUPP))
|
|
ret = -EOPNOTSUPP;
|
|
|
|
bio_put(bio);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(submit_bh);
|
|
|
|
/**
|
|
* ll_rw_block: low-level access to block devices (DEPRECATED)
|
|
* @rw: whether to %READ or %WRITE or maybe %READA (readahead)
|
|
* @nr: number of &struct buffer_heads in the array
|
|
* @bhs: array of pointers to &struct buffer_head
|
|
*
|
|
* ll_rw_block() takes an array of pointers to &struct buffer_heads, and
|
|
* requests an I/O operation on them, either a %READ or a %WRITE. The third
|
|
* %READA option is described in the documentation for generic_make_request()
|
|
* which ll_rw_block() calls.
|
|
*
|
|
* This function drops any buffer that it cannot get a lock on (with the
|
|
* BH_Lock state bit), any buffer that appears to be clean when doing a write
|
|
* request, and any buffer that appears to be up-to-date when doing read
|
|
* request. Further it marks as clean buffers that are processed for
|
|
* writing (the buffer cache won't assume that they are actually clean
|
|
* until the buffer gets unlocked).
|
|
*
|
|
* ll_rw_block sets b_end_io to simple completion handler that marks
|
|
* the buffer up-to-date (if approriate), unlocks the buffer and wakes
|
|
* any waiters.
|
|
*
|
|
* All of the buffers must be for the same device, and must also be a
|
|
* multiple of the current approved size for the device.
|
|
*/
|
|
void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < nr; i++) {
|
|
struct buffer_head *bh = bhs[i];
|
|
|
|
if (!trylock_buffer(bh))
|
|
continue;
|
|
if (rw == WRITE) {
|
|
if (test_clear_buffer_dirty(bh)) {
|
|
bh->b_end_io = end_buffer_write_sync;
|
|
get_bh(bh);
|
|
submit_bh(WRITE, bh);
|
|
continue;
|
|
}
|
|
} else {
|
|
if (!buffer_uptodate(bh)) {
|
|
bh->b_end_io = end_buffer_read_sync;
|
|
get_bh(bh);
|
|
submit_bh(rw, bh);
|
|
continue;
|
|
}
|
|
}
|
|
unlock_buffer(bh);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(ll_rw_block);
|
|
|
|
void write_dirty_buffer(struct buffer_head *bh, int rw)
|
|
{
|
|
lock_buffer(bh);
|
|
if (!test_clear_buffer_dirty(bh)) {
|
|
unlock_buffer(bh);
|
|
return;
|
|
}
|
|
bh->b_end_io = end_buffer_write_sync;
|
|
get_bh(bh);
|
|
submit_bh(rw, bh);
|
|
}
|
|
EXPORT_SYMBOL(write_dirty_buffer);
|
|
|
|
/*
|
|
* For a data-integrity writeout, we need to wait upon any in-progress I/O
|
|
* and then start new I/O and then wait upon it. The caller must have a ref on
|
|
* the buffer_head.
|
|
*/
|
|
int __sync_dirty_buffer(struct buffer_head *bh, int rw)
|
|
{
|
|
int ret = 0;
|
|
|
|
WARN_ON(atomic_read(&bh->b_count) < 1);
|
|
lock_buffer(bh);
|
|
if (test_clear_buffer_dirty(bh)) {
|
|
get_bh(bh);
|
|
bh->b_end_io = end_buffer_write_sync;
|
|
ret = submit_bh(rw, bh);
|
|
wait_on_buffer(bh);
|
|
if (!ret && !buffer_uptodate(bh))
|
|
ret = -EIO;
|
|
} else {
|
|
unlock_buffer(bh);
|
|
}
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(__sync_dirty_buffer);
|
|
|
|
int sync_dirty_buffer(struct buffer_head *bh)
|
|
{
|
|
return __sync_dirty_buffer(bh, WRITE_SYNC);
|
|
}
|
|
EXPORT_SYMBOL(sync_dirty_buffer);
|
|
|
|
/*
|
|
* try_to_free_buffers() checks if all the buffers on this particular page
|
|
* are unused, and releases them if so.
|
|
*
|
|
* Exclusion against try_to_free_buffers may be obtained by either
|
|
* locking the page or by holding its mapping's private_lock.
|
|
*
|
|
* If the page is dirty but all the buffers are clean then we need to
|
|
* be sure to mark the page clean as well. This is because the page
|
|
* may be against a block device, and a later reattachment of buffers
|
|
* to a dirty page will set *all* buffers dirty. Which would corrupt
|
|
* filesystem data on the same device.
|
|
*
|
|
* The same applies to regular filesystem pages: if all the buffers are
|
|
* clean then we set the page clean and proceed. To do that, we require
|
|
* total exclusion from __set_page_dirty_buffers(). That is obtained with
|
|
* private_lock.
|
|
*
|
|
* try_to_free_buffers() is non-blocking.
|
|
*/
|
|
static inline int buffer_busy(struct buffer_head *bh)
|
|
{
|
|
return atomic_read(&bh->b_count) |
|
|
(bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
|
|
}
|
|
|
|
static int
|
|
drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
|
|
{
|
|
struct buffer_head *head = page_buffers(page);
|
|
struct buffer_head *bh;
|
|
|
|
bh = head;
|
|
do {
|
|
if (buffer_write_io_error(bh) && page->mapping)
|
|
set_bit(AS_EIO, &page->mapping->flags);
|
|
if (buffer_busy(bh))
|
|
goto failed;
|
|
bh = bh->b_this_page;
|
|
} while (bh != head);
|
|
|
|
do {
|
|
struct buffer_head *next = bh->b_this_page;
|
|
|
|
if (bh->b_assoc_map)
|
|
__remove_assoc_queue(bh);
|
|
bh = next;
|
|
} while (bh != head);
|
|
*buffers_to_free = head;
|
|
__clear_page_buffers(page);
|
|
return 1;
|
|
failed:
|
|
return 0;
|
|
}
|
|
|
|
int try_to_free_buffers(struct page *page)
|
|
{
|
|
struct address_space * const mapping = page->mapping;
|
|
struct buffer_head *buffers_to_free = NULL;
|
|
int ret = 0;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
if (PageWriteback(page))
|
|
return 0;
|
|
|
|
if (mapping == NULL) { /* can this still happen? */
|
|
ret = drop_buffers(page, &buffers_to_free);
|
|
goto out;
|
|
}
|
|
|
|
spin_lock(&mapping->private_lock);
|
|
ret = drop_buffers(page, &buffers_to_free);
|
|
|
|
/*
|
|
* If the filesystem writes its buffers by hand (eg ext3)
|
|
* then we can have clean buffers against a dirty page. We
|
|
* clean the page here; otherwise the VM will never notice
|
|
* that the filesystem did any IO at all.
|
|
*
|
|
* Also, during truncate, discard_buffer will have marked all
|
|
* the page's buffers clean. We discover that here and clean
|
|
* the page also.
|
|
*
|
|
* private_lock must be held over this entire operation in order
|
|
* to synchronise against __set_page_dirty_buffers and prevent the
|
|
* dirty bit from being lost.
|
|
*/
|
|
if (ret)
|
|
cancel_dirty_page(page, PAGE_CACHE_SIZE);
|
|
spin_unlock(&mapping->private_lock);
|
|
out:
|
|
if (buffers_to_free) {
|
|
struct buffer_head *bh = buffers_to_free;
|
|
|
|
do {
|
|
struct buffer_head *next = bh->b_this_page;
|
|
free_buffer_head(bh);
|
|
bh = next;
|
|
} while (bh != buffers_to_free);
|
|
}
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(try_to_free_buffers);
|
|
|
|
/*
|
|
* There are no bdflush tunables left. But distributions are
|
|
* still running obsolete flush daemons, so we terminate them here.
|
|
*
|
|
* Use of bdflush() is deprecated and will be removed in a future kernel.
|
|
* The `flush-X' kernel threads fully replace bdflush daemons and this call.
|
|
*/
|
|
SYSCALL_DEFINE2(bdflush, int, func, long, data)
|
|
{
|
|
static int msg_count;
|
|
|
|
if (!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
|
|
if (msg_count < 5) {
|
|
msg_count++;
|
|
printk(KERN_INFO
|
|
"warning: process `%s' used the obsolete bdflush"
|
|
" system call\n", current->comm);
|
|
printk(KERN_INFO "Fix your initscripts?\n");
|
|
}
|
|
|
|
if (func == 1)
|
|
do_exit(0);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Buffer-head allocation
|
|
*/
|
|
static struct kmem_cache *bh_cachep;
|
|
|
|
/*
|
|
* Once the number of bh's in the machine exceeds this level, we start
|
|
* stripping them in writeback.
|
|
*/
|
|
static int max_buffer_heads;
|
|
|
|
int buffer_heads_over_limit;
|
|
|
|
struct bh_accounting {
|
|
int nr; /* Number of live bh's */
|
|
int ratelimit; /* Limit cacheline bouncing */
|
|
};
|
|
|
|
static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
|
|
|
|
static void recalc_bh_state(void)
|
|
{
|
|
int i;
|
|
int tot = 0;
|
|
|
|
if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
|
|
return;
|
|
__this_cpu_write(bh_accounting.ratelimit, 0);
|
|
for_each_online_cpu(i)
|
|
tot += per_cpu(bh_accounting, i).nr;
|
|
buffer_heads_over_limit = (tot > max_buffer_heads);
|
|
}
|
|
|
|
struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
|
|
{
|
|
struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
|
|
if (ret) {
|
|
INIT_LIST_HEAD(&ret->b_assoc_buffers);
|
|
preempt_disable();
|
|
__this_cpu_inc(bh_accounting.nr);
|
|
recalc_bh_state();
|
|
preempt_enable();
|
|
}
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(alloc_buffer_head);
|
|
|
|
void free_buffer_head(struct buffer_head *bh)
|
|
{
|
|
BUG_ON(!list_empty(&bh->b_assoc_buffers));
|
|
kmem_cache_free(bh_cachep, bh);
|
|
preempt_disable();
|
|
__this_cpu_dec(bh_accounting.nr);
|
|
recalc_bh_state();
|
|
preempt_enable();
|
|
}
|
|
EXPORT_SYMBOL(free_buffer_head);
|
|
|
|
static void buffer_exit_cpu(int cpu)
|
|
{
|
|
int i;
|
|
struct bh_lru *b = &per_cpu(bh_lrus, cpu);
|
|
|
|
for (i = 0; i < BH_LRU_SIZE; i++) {
|
|
brelse(b->bhs[i]);
|
|
b->bhs[i] = NULL;
|
|
}
|
|
this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
|
|
per_cpu(bh_accounting, cpu).nr = 0;
|
|
}
|
|
|
|
static int buffer_cpu_notify(struct notifier_block *self,
|
|
unsigned long action, void *hcpu)
|
|
{
|
|
if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
|
|
buffer_exit_cpu((unsigned long)hcpu);
|
|
return NOTIFY_OK;
|
|
}
|
|
|
|
/**
|
|
* bh_uptodate_or_lock - Test whether the buffer is uptodate
|
|
* @bh: struct buffer_head
|
|
*
|
|
* Return true if the buffer is up-to-date and false,
|
|
* with the buffer locked, if not.
|
|
*/
|
|
int bh_uptodate_or_lock(struct buffer_head *bh)
|
|
{
|
|
if (!buffer_uptodate(bh)) {
|
|
lock_buffer(bh);
|
|
if (!buffer_uptodate(bh))
|
|
return 0;
|
|
unlock_buffer(bh);
|
|
}
|
|
return 1;
|
|
}
|
|
EXPORT_SYMBOL(bh_uptodate_or_lock);
|
|
|
|
/**
|
|
* bh_submit_read - Submit a locked buffer for reading
|
|
* @bh: struct buffer_head
|
|
*
|
|
* Returns zero on success and -EIO on error.
|
|
*/
|
|
int bh_submit_read(struct buffer_head *bh)
|
|
{
|
|
BUG_ON(!buffer_locked(bh));
|
|
|
|
if (buffer_uptodate(bh)) {
|
|
unlock_buffer(bh);
|
|
return 0;
|
|
}
|
|
|
|
get_bh(bh);
|
|
bh->b_end_io = end_buffer_read_sync;
|
|
submit_bh(READ, bh);
|
|
wait_on_buffer(bh);
|
|
if (buffer_uptodate(bh))
|
|
return 0;
|
|
return -EIO;
|
|
}
|
|
EXPORT_SYMBOL(bh_submit_read);
|
|
|
|
void __init buffer_init(void)
|
|
{
|
|
int nrpages;
|
|
|
|
bh_cachep = kmem_cache_create("buffer_head",
|
|
sizeof(struct buffer_head), 0,
|
|
(SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
|
|
SLAB_MEM_SPREAD),
|
|
NULL);
|
|
|
|
/*
|
|
* Limit the bh occupancy to 10% of ZONE_NORMAL
|
|
*/
|
|
nrpages = (nr_free_buffer_pages() * 10) / 100;
|
|
max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
|
|
hotcpu_notifier(buffer_cpu_notify, 0);
|
|
}
|