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![Linus Torvalds](/assets/img/avatar_default.png)
We had to revert the pluggin in writeback_sb_inodes() because the wb->list_lock is held, but we could easily plug at a higher level before taking that lock, and unplug after releasing it. This does that. Chris will run performance numbers, just to verify that this approach is comparable to the alternative (we could just drop and re-take the lock around the blk_finish_plug() rather than these two commits. I'd have preferred waiting for actual performance numbers before picking one approach over the other, but I don't want to release rc1 with the known "sleeping function called from invalid context" issue, so I'll pick this cleanup version for now. But if the numbers show that we really want to plug just at the writeback_sb_inodes() level, and we should just play ugly games with the spinlock, we'll switch to that. Cc: Chris Mason <clm@fb.com> Cc: Josef Bacik <jbacik@fb.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Neil Brown <neilb@suse.de> Cc: Jan Kara <jack@suse.cz> Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2325 lines
67 KiB
C
2325 lines
67 KiB
C
/*
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* fs/fs-writeback.c
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*
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* Copyright (C) 2002, Linus Torvalds.
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*
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* Contains all the functions related to writing back and waiting
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* upon dirty inodes against superblocks, and writing back dirty
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* pages against inodes. ie: data writeback. Writeout of the
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* inode itself is not handled here.
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*
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* 10Apr2002 Andrew Morton
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* Split out of fs/inode.c
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* Additions for address_space-based writeback
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*/
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#include <linux/kernel.h>
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#include <linux/export.h>
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#include <linux/spinlock.h>
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#include <linux/slab.h>
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#include <linux/sched.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/pagemap.h>
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#include <linux/kthread.h>
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#include <linux/writeback.h>
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#include <linux/blkdev.h>
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#include <linux/backing-dev.h>
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#include <linux/tracepoint.h>
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#include <linux/device.h>
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#include <linux/memcontrol.h>
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#include "internal.h"
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/*
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* 4MB minimal write chunk size
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*/
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#define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_CACHE_SHIFT - 10))
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struct wb_completion {
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atomic_t cnt;
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};
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/*
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* Passed into wb_writeback(), essentially a subset of writeback_control
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*/
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struct wb_writeback_work {
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long nr_pages;
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struct super_block *sb;
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unsigned long *older_than_this;
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enum writeback_sync_modes sync_mode;
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unsigned int tagged_writepages:1;
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unsigned int for_kupdate:1;
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unsigned int range_cyclic:1;
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unsigned int for_background:1;
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unsigned int for_sync:1; /* sync(2) WB_SYNC_ALL writeback */
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unsigned int auto_free:1; /* free on completion */
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enum wb_reason reason; /* why was writeback initiated? */
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struct list_head list; /* pending work list */
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struct wb_completion *done; /* set if the caller waits */
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};
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/*
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* If one wants to wait for one or more wb_writeback_works, each work's
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* ->done should be set to a wb_completion defined using the following
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* macro. Once all work items are issued with wb_queue_work(), the caller
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* can wait for the completion of all using wb_wait_for_completion(). Work
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* items which are waited upon aren't freed automatically on completion.
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*/
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#define DEFINE_WB_COMPLETION_ONSTACK(cmpl) \
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struct wb_completion cmpl = { \
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.cnt = ATOMIC_INIT(1), \
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}
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/*
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* If an inode is constantly having its pages dirtied, but then the
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* updates stop dirtytime_expire_interval seconds in the past, it's
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* possible for the worst case time between when an inode has its
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* timestamps updated and when they finally get written out to be two
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* dirtytime_expire_intervals. We set the default to 12 hours (in
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* seconds), which means most of the time inodes will have their
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* timestamps written to disk after 12 hours, but in the worst case a
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* few inodes might not their timestamps updated for 24 hours.
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*/
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unsigned int dirtytime_expire_interval = 12 * 60 * 60;
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static inline struct inode *wb_inode(struct list_head *head)
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{
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return list_entry(head, struct inode, i_io_list);
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}
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/*
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* Include the creation of the trace points after defining the
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* wb_writeback_work structure and inline functions so that the definition
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* remains local to this file.
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*/
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#define CREATE_TRACE_POINTS
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#include <trace/events/writeback.h>
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EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepage);
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static bool wb_io_lists_populated(struct bdi_writeback *wb)
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{
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if (wb_has_dirty_io(wb)) {
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return false;
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} else {
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set_bit(WB_has_dirty_io, &wb->state);
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WARN_ON_ONCE(!wb->avg_write_bandwidth);
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atomic_long_add(wb->avg_write_bandwidth,
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&wb->bdi->tot_write_bandwidth);
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return true;
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}
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}
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static void wb_io_lists_depopulated(struct bdi_writeback *wb)
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{
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if (wb_has_dirty_io(wb) && list_empty(&wb->b_dirty) &&
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list_empty(&wb->b_io) && list_empty(&wb->b_more_io)) {
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clear_bit(WB_has_dirty_io, &wb->state);
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WARN_ON_ONCE(atomic_long_sub_return(wb->avg_write_bandwidth,
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&wb->bdi->tot_write_bandwidth) < 0);
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}
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}
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/**
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* inode_io_list_move_locked - move an inode onto a bdi_writeback IO list
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* @inode: inode to be moved
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* @wb: target bdi_writeback
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* @head: one of @wb->b_{dirty|io|more_io}
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*
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* Move @inode->i_io_list to @list of @wb and set %WB_has_dirty_io.
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* Returns %true if @inode is the first occupant of the !dirty_time IO
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* lists; otherwise, %false.
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*/
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static bool inode_io_list_move_locked(struct inode *inode,
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struct bdi_writeback *wb,
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struct list_head *head)
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{
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assert_spin_locked(&wb->list_lock);
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list_move(&inode->i_io_list, head);
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/* dirty_time doesn't count as dirty_io until expiration */
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if (head != &wb->b_dirty_time)
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return wb_io_lists_populated(wb);
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wb_io_lists_depopulated(wb);
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return false;
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}
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/**
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* inode_io_list_del_locked - remove an inode from its bdi_writeback IO list
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* @inode: inode to be removed
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* @wb: bdi_writeback @inode is being removed from
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*
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* Remove @inode which may be on one of @wb->b_{dirty|io|more_io} lists and
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* clear %WB_has_dirty_io if all are empty afterwards.
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*/
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static void inode_io_list_del_locked(struct inode *inode,
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struct bdi_writeback *wb)
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{
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assert_spin_locked(&wb->list_lock);
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list_del_init(&inode->i_io_list);
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wb_io_lists_depopulated(wb);
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}
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static void wb_wakeup(struct bdi_writeback *wb)
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{
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spin_lock_bh(&wb->work_lock);
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if (test_bit(WB_registered, &wb->state))
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mod_delayed_work(bdi_wq, &wb->dwork, 0);
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spin_unlock_bh(&wb->work_lock);
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}
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static void wb_queue_work(struct bdi_writeback *wb,
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struct wb_writeback_work *work)
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{
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trace_writeback_queue(wb, work);
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spin_lock_bh(&wb->work_lock);
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if (!test_bit(WB_registered, &wb->state))
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goto out_unlock;
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if (work->done)
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atomic_inc(&work->done->cnt);
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list_add_tail(&work->list, &wb->work_list);
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mod_delayed_work(bdi_wq, &wb->dwork, 0);
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out_unlock:
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spin_unlock_bh(&wb->work_lock);
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}
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/**
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* wb_wait_for_completion - wait for completion of bdi_writeback_works
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* @bdi: bdi work items were issued to
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* @done: target wb_completion
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*
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* Wait for one or more work items issued to @bdi with their ->done field
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* set to @done, which should have been defined with
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* DEFINE_WB_COMPLETION_ONSTACK(). This function returns after all such
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* work items are completed. Work items which are waited upon aren't freed
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* automatically on completion.
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*/
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static void wb_wait_for_completion(struct backing_dev_info *bdi,
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struct wb_completion *done)
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{
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atomic_dec(&done->cnt); /* put down the initial count */
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wait_event(bdi->wb_waitq, !atomic_read(&done->cnt));
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}
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#ifdef CONFIG_CGROUP_WRITEBACK
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/* parameters for foreign inode detection, see wb_detach_inode() */
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#define WB_FRN_TIME_SHIFT 13 /* 1s = 2^13, upto 8 secs w/ 16bit */
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#define WB_FRN_TIME_AVG_SHIFT 3 /* avg = avg * 7/8 + new * 1/8 */
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#define WB_FRN_TIME_CUT_DIV 2 /* ignore rounds < avg / 2 */
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#define WB_FRN_TIME_PERIOD (2 * (1 << WB_FRN_TIME_SHIFT)) /* 2s */
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#define WB_FRN_HIST_SLOTS 16 /* inode->i_wb_frn_history is 16bit */
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#define WB_FRN_HIST_UNIT (WB_FRN_TIME_PERIOD / WB_FRN_HIST_SLOTS)
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/* each slot's duration is 2s / 16 */
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#define WB_FRN_HIST_THR_SLOTS (WB_FRN_HIST_SLOTS / 2)
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/* if foreign slots >= 8, switch */
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#define WB_FRN_HIST_MAX_SLOTS (WB_FRN_HIST_THR_SLOTS / 2 + 1)
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/* one round can affect upto 5 slots */
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void __inode_attach_wb(struct inode *inode, struct page *page)
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{
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struct backing_dev_info *bdi = inode_to_bdi(inode);
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struct bdi_writeback *wb = NULL;
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if (inode_cgwb_enabled(inode)) {
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struct cgroup_subsys_state *memcg_css;
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if (page) {
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memcg_css = mem_cgroup_css_from_page(page);
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wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
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} else {
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/* must pin memcg_css, see wb_get_create() */
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memcg_css = task_get_css(current, memory_cgrp_id);
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wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
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css_put(memcg_css);
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}
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}
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if (!wb)
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wb = &bdi->wb;
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/*
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* There may be multiple instances of this function racing to
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* update the same inode. Use cmpxchg() to tell the winner.
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*/
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if (unlikely(cmpxchg(&inode->i_wb, NULL, wb)))
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wb_put(wb);
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}
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/**
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* locked_inode_to_wb_and_lock_list - determine a locked inode's wb and lock it
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* @inode: inode of interest with i_lock held
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*
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* Returns @inode's wb with its list_lock held. @inode->i_lock must be
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* held on entry and is released on return. The returned wb is guaranteed
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* to stay @inode's associated wb until its list_lock is released.
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*/
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static struct bdi_writeback *
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locked_inode_to_wb_and_lock_list(struct inode *inode)
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__releases(&inode->i_lock)
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__acquires(&wb->list_lock)
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{
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while (true) {
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struct bdi_writeback *wb = inode_to_wb(inode);
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/*
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* inode_to_wb() association is protected by both
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* @inode->i_lock and @wb->list_lock but list_lock nests
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* outside i_lock. Drop i_lock and verify that the
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* association hasn't changed after acquiring list_lock.
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*/
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wb_get(wb);
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spin_unlock(&inode->i_lock);
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spin_lock(&wb->list_lock);
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wb_put(wb); /* not gonna deref it anymore */
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/* i_wb may have changed inbetween, can't use inode_to_wb() */
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if (likely(wb == inode->i_wb))
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return wb; /* @inode already has ref */
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spin_unlock(&wb->list_lock);
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cpu_relax();
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spin_lock(&inode->i_lock);
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}
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}
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/**
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* inode_to_wb_and_lock_list - determine an inode's wb and lock it
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* @inode: inode of interest
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*
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* Same as locked_inode_to_wb_and_lock_list() but @inode->i_lock isn't held
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* on entry.
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*/
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static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode)
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__acquires(&wb->list_lock)
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{
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spin_lock(&inode->i_lock);
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return locked_inode_to_wb_and_lock_list(inode);
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}
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struct inode_switch_wbs_context {
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struct inode *inode;
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struct bdi_writeback *new_wb;
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struct rcu_head rcu_head;
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struct work_struct work;
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};
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static void inode_switch_wbs_work_fn(struct work_struct *work)
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{
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struct inode_switch_wbs_context *isw =
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container_of(work, struct inode_switch_wbs_context, work);
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struct inode *inode = isw->inode;
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struct address_space *mapping = inode->i_mapping;
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struct bdi_writeback *old_wb = inode->i_wb;
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struct bdi_writeback *new_wb = isw->new_wb;
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struct radix_tree_iter iter;
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bool switched = false;
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void **slot;
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/*
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* By the time control reaches here, RCU grace period has passed
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* since I_WB_SWITCH assertion and all wb stat update transactions
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* between unlocked_inode_to_wb_begin/end() are guaranteed to be
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* synchronizing against mapping->tree_lock.
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*
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* Grabbing old_wb->list_lock, inode->i_lock and mapping->tree_lock
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* gives us exclusion against all wb related operations on @inode
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* including IO list manipulations and stat updates.
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*/
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if (old_wb < new_wb) {
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spin_lock(&old_wb->list_lock);
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spin_lock_nested(&new_wb->list_lock, SINGLE_DEPTH_NESTING);
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} else {
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spin_lock(&new_wb->list_lock);
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spin_lock_nested(&old_wb->list_lock, SINGLE_DEPTH_NESTING);
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}
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spin_lock(&inode->i_lock);
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spin_lock_irq(&mapping->tree_lock);
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/*
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* Once I_FREEING is visible under i_lock, the eviction path owns
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* the inode and we shouldn't modify ->i_io_list.
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*/
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if (unlikely(inode->i_state & I_FREEING))
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goto skip_switch;
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/*
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* Count and transfer stats. Note that PAGECACHE_TAG_DIRTY points
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* to possibly dirty pages while PAGECACHE_TAG_WRITEBACK points to
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* pages actually under underwriteback.
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*/
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radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter, 0,
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PAGECACHE_TAG_DIRTY) {
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struct page *page = radix_tree_deref_slot_protected(slot,
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&mapping->tree_lock);
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if (likely(page) && PageDirty(page)) {
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__dec_wb_stat(old_wb, WB_RECLAIMABLE);
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__inc_wb_stat(new_wb, WB_RECLAIMABLE);
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}
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}
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radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter, 0,
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PAGECACHE_TAG_WRITEBACK) {
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struct page *page = radix_tree_deref_slot_protected(slot,
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&mapping->tree_lock);
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if (likely(page)) {
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WARN_ON_ONCE(!PageWriteback(page));
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__dec_wb_stat(old_wb, WB_WRITEBACK);
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__inc_wb_stat(new_wb, WB_WRITEBACK);
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}
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}
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wb_get(new_wb);
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/*
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* Transfer to @new_wb's IO list if necessary. The specific list
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* @inode was on is ignored and the inode is put on ->b_dirty which
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* is always correct including from ->b_dirty_time. The transfer
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* preserves @inode->dirtied_when ordering.
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*/
|
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if (!list_empty(&inode->i_io_list)) {
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struct inode *pos;
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inode_io_list_del_locked(inode, old_wb);
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inode->i_wb = new_wb;
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list_for_each_entry(pos, &new_wb->b_dirty, i_io_list)
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if (time_after_eq(inode->dirtied_when,
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pos->dirtied_when))
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break;
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inode_io_list_move_locked(inode, new_wb, pos->i_io_list.prev);
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} else {
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inode->i_wb = new_wb;
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}
|
|
|
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/* ->i_wb_frn updates may race wbc_detach_inode() but doesn't matter */
|
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inode->i_wb_frn_winner = 0;
|
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inode->i_wb_frn_avg_time = 0;
|
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inode->i_wb_frn_history = 0;
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switched = true;
|
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skip_switch:
|
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/*
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* Paired with load_acquire in unlocked_inode_to_wb_begin() and
|
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* ensures that the new wb is visible if they see !I_WB_SWITCH.
|
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*/
|
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smp_store_release(&inode->i_state, inode->i_state & ~I_WB_SWITCH);
|
|
|
|
spin_unlock_irq(&mapping->tree_lock);
|
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spin_unlock(&inode->i_lock);
|
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spin_unlock(&new_wb->list_lock);
|
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spin_unlock(&old_wb->list_lock);
|
|
|
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if (switched) {
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wb_wakeup(new_wb);
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wb_put(old_wb);
|
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}
|
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wb_put(new_wb);
|
|
|
|
iput(inode);
|
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kfree(isw);
|
|
}
|
|
|
|
static void inode_switch_wbs_rcu_fn(struct rcu_head *rcu_head)
|
|
{
|
|
struct inode_switch_wbs_context *isw = container_of(rcu_head,
|
|
struct inode_switch_wbs_context, rcu_head);
|
|
|
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/* needs to grab bh-unsafe locks, bounce to work item */
|
|
INIT_WORK(&isw->work, inode_switch_wbs_work_fn);
|
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schedule_work(&isw->work);
|
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}
|
|
|
|
/**
|
|
* inode_switch_wbs - change the wb association of an inode
|
|
* @inode: target inode
|
|
* @new_wb_id: ID of the new wb
|
|
*
|
|
* Switch @inode's wb association to the wb identified by @new_wb_id. The
|
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* switching is performed asynchronously and may fail silently.
|
|
*/
|
|
static void inode_switch_wbs(struct inode *inode, int new_wb_id)
|
|
{
|
|
struct backing_dev_info *bdi = inode_to_bdi(inode);
|
|
struct cgroup_subsys_state *memcg_css;
|
|
struct inode_switch_wbs_context *isw;
|
|
|
|
/* noop if seems to be already in progress */
|
|
if (inode->i_state & I_WB_SWITCH)
|
|
return;
|
|
|
|
isw = kzalloc(sizeof(*isw), GFP_ATOMIC);
|
|
if (!isw)
|
|
return;
|
|
|
|
/* find and pin the new wb */
|
|
rcu_read_lock();
|
|
memcg_css = css_from_id(new_wb_id, &memory_cgrp_subsys);
|
|
if (memcg_css)
|
|
isw->new_wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
|
|
rcu_read_unlock();
|
|
if (!isw->new_wb)
|
|
goto out_free;
|
|
|
|
/* while holding I_WB_SWITCH, no one else can update the association */
|
|
spin_lock(&inode->i_lock);
|
|
if (inode->i_state & (I_WB_SWITCH | I_FREEING) ||
|
|
inode_to_wb(inode) == isw->new_wb) {
|
|
spin_unlock(&inode->i_lock);
|
|
goto out_free;
|
|
}
|
|
inode->i_state |= I_WB_SWITCH;
|
|
spin_unlock(&inode->i_lock);
|
|
|
|
ihold(inode);
|
|
isw->inode = inode;
|
|
|
|
/*
|
|
* In addition to synchronizing among switchers, I_WB_SWITCH tells
|
|
* the RCU protected stat update paths to grab the mapping's
|
|
* tree_lock so that stat transfer can synchronize against them.
|
|
* Let's continue after I_WB_SWITCH is guaranteed to be visible.
|
|
*/
|
|
call_rcu(&isw->rcu_head, inode_switch_wbs_rcu_fn);
|
|
return;
|
|
|
|
out_free:
|
|
if (isw->new_wb)
|
|
wb_put(isw->new_wb);
|
|
kfree(isw);
|
|
}
|
|
|
|
/**
|
|
* wbc_attach_and_unlock_inode - associate wbc with target inode and unlock it
|
|
* @wbc: writeback_control of interest
|
|
* @inode: target inode
|
|
*
|
|
* @inode is locked and about to be written back under the control of @wbc.
|
|
* Record @inode's writeback context into @wbc and unlock the i_lock. On
|
|
* writeback completion, wbc_detach_inode() should be called. This is used
|
|
* to track the cgroup writeback context.
|
|
*/
|
|
void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
|
|
struct inode *inode)
|
|
{
|
|
if (!inode_cgwb_enabled(inode)) {
|
|
spin_unlock(&inode->i_lock);
|
|
return;
|
|
}
|
|
|
|
wbc->wb = inode_to_wb(inode);
|
|
wbc->inode = inode;
|
|
|
|
wbc->wb_id = wbc->wb->memcg_css->id;
|
|
wbc->wb_lcand_id = inode->i_wb_frn_winner;
|
|
wbc->wb_tcand_id = 0;
|
|
wbc->wb_bytes = 0;
|
|
wbc->wb_lcand_bytes = 0;
|
|
wbc->wb_tcand_bytes = 0;
|
|
|
|
wb_get(wbc->wb);
|
|
spin_unlock(&inode->i_lock);
|
|
|
|
/*
|
|
* A dying wb indicates that the memcg-blkcg mapping has changed
|
|
* and a new wb is already serving the memcg. Switch immediately.
|
|
*/
|
|
if (unlikely(wb_dying(wbc->wb)))
|
|
inode_switch_wbs(inode, wbc->wb_id);
|
|
}
|
|
|
|
/**
|
|
* wbc_detach_inode - disassociate wbc from inode and perform foreign detection
|
|
* @wbc: writeback_control of the just finished writeback
|
|
*
|
|
* To be called after a writeback attempt of an inode finishes and undoes
|
|
* wbc_attach_and_unlock_inode(). Can be called under any context.
|
|
*
|
|
* As concurrent write sharing of an inode is expected to be very rare and
|
|
* memcg only tracks page ownership on first-use basis severely confining
|
|
* the usefulness of such sharing, cgroup writeback tracks ownership
|
|
* per-inode. While the support for concurrent write sharing of an inode
|
|
* is deemed unnecessary, an inode being written to by different cgroups at
|
|
* different points in time is a lot more common, and, more importantly,
|
|
* charging only by first-use can too readily lead to grossly incorrect
|
|
* behaviors (single foreign page can lead to gigabytes of writeback to be
|
|
* incorrectly attributed).
|
|
*
|
|
* To resolve this issue, cgroup writeback detects the majority dirtier of
|
|
* an inode and transfers the ownership to it. To avoid unnnecessary
|
|
* oscillation, the detection mechanism keeps track of history and gives
|
|
* out the switch verdict only if the foreign usage pattern is stable over
|
|
* a certain amount of time and/or writeback attempts.
|
|
*
|
|
* On each writeback attempt, @wbc tries to detect the majority writer
|
|
* using Boyer-Moore majority vote algorithm. In addition to the byte
|
|
* count from the majority voting, it also counts the bytes written for the
|
|
* current wb and the last round's winner wb (max of last round's current
|
|
* wb, the winner from two rounds ago, and the last round's majority
|
|
* candidate). Keeping track of the historical winner helps the algorithm
|
|
* to semi-reliably detect the most active writer even when it's not the
|
|
* absolute majority.
|
|
*
|
|
* Once the winner of the round is determined, whether the winner is
|
|
* foreign or not and how much IO time the round consumed is recorded in
|
|
* inode->i_wb_frn_history. If the amount of recorded foreign IO time is
|
|
* over a certain threshold, the switch verdict is given.
|
|
*/
|
|
void wbc_detach_inode(struct writeback_control *wbc)
|
|
{
|
|
struct bdi_writeback *wb = wbc->wb;
|
|
struct inode *inode = wbc->inode;
|
|
unsigned long avg_time, max_bytes, max_time;
|
|
u16 history;
|
|
int max_id;
|
|
|
|
if (!wb)
|
|
return;
|
|
|
|
history = inode->i_wb_frn_history;
|
|
avg_time = inode->i_wb_frn_avg_time;
|
|
|
|
/* pick the winner of this round */
|
|
if (wbc->wb_bytes >= wbc->wb_lcand_bytes &&
|
|
wbc->wb_bytes >= wbc->wb_tcand_bytes) {
|
|
max_id = wbc->wb_id;
|
|
max_bytes = wbc->wb_bytes;
|
|
} else if (wbc->wb_lcand_bytes >= wbc->wb_tcand_bytes) {
|
|
max_id = wbc->wb_lcand_id;
|
|
max_bytes = wbc->wb_lcand_bytes;
|
|
} else {
|
|
max_id = wbc->wb_tcand_id;
|
|
max_bytes = wbc->wb_tcand_bytes;
|
|
}
|
|
|
|
/*
|
|
* Calculate the amount of IO time the winner consumed and fold it
|
|
* into the running average kept per inode. If the consumed IO
|
|
* time is lower than avag / WB_FRN_TIME_CUT_DIV, ignore it for
|
|
* deciding whether to switch or not. This is to prevent one-off
|
|
* small dirtiers from skewing the verdict.
|
|
*/
|
|
max_time = DIV_ROUND_UP((max_bytes >> PAGE_SHIFT) << WB_FRN_TIME_SHIFT,
|
|
wb->avg_write_bandwidth);
|
|
if (avg_time)
|
|
avg_time += (max_time >> WB_FRN_TIME_AVG_SHIFT) -
|
|
(avg_time >> WB_FRN_TIME_AVG_SHIFT);
|
|
else
|
|
avg_time = max_time; /* immediate catch up on first run */
|
|
|
|
if (max_time >= avg_time / WB_FRN_TIME_CUT_DIV) {
|
|
int slots;
|
|
|
|
/*
|
|
* The switch verdict is reached if foreign wb's consume
|
|
* more than a certain proportion of IO time in a
|
|
* WB_FRN_TIME_PERIOD. This is loosely tracked by 16 slot
|
|
* history mask where each bit represents one sixteenth of
|
|
* the period. Determine the number of slots to shift into
|
|
* history from @max_time.
|
|
*/
|
|
slots = min(DIV_ROUND_UP(max_time, WB_FRN_HIST_UNIT),
|
|
(unsigned long)WB_FRN_HIST_MAX_SLOTS);
|
|
history <<= slots;
|
|
if (wbc->wb_id != max_id)
|
|
history |= (1U << slots) - 1;
|
|
|
|
/*
|
|
* Switch if the current wb isn't the consistent winner.
|
|
* If there are multiple closely competing dirtiers, the
|
|
* inode may switch across them repeatedly over time, which
|
|
* is okay. The main goal is avoiding keeping an inode on
|
|
* the wrong wb for an extended period of time.
|
|
*/
|
|
if (hweight32(history) > WB_FRN_HIST_THR_SLOTS)
|
|
inode_switch_wbs(inode, max_id);
|
|
}
|
|
|
|
/*
|
|
* Multiple instances of this function may race to update the
|
|
* following fields but we don't mind occassional inaccuracies.
|
|
*/
|
|
inode->i_wb_frn_winner = max_id;
|
|
inode->i_wb_frn_avg_time = min(avg_time, (unsigned long)U16_MAX);
|
|
inode->i_wb_frn_history = history;
|
|
|
|
wb_put(wbc->wb);
|
|
wbc->wb = NULL;
|
|
}
|
|
|
|
/**
|
|
* wbc_account_io - account IO issued during writeback
|
|
* @wbc: writeback_control of the writeback in progress
|
|
* @page: page being written out
|
|
* @bytes: number of bytes being written out
|
|
*
|
|
* @bytes from @page are about to written out during the writeback
|
|
* controlled by @wbc. Keep the book for foreign inode detection. See
|
|
* wbc_detach_inode().
|
|
*/
|
|
void wbc_account_io(struct writeback_control *wbc, struct page *page,
|
|
size_t bytes)
|
|
{
|
|
int id;
|
|
|
|
/*
|
|
* pageout() path doesn't attach @wbc to the inode being written
|
|
* out. This is intentional as we don't want the function to block
|
|
* behind a slow cgroup. Ultimately, we want pageout() to kick off
|
|
* regular writeback instead of writing things out itself.
|
|
*/
|
|
if (!wbc->wb)
|
|
return;
|
|
|
|
rcu_read_lock();
|
|
id = mem_cgroup_css_from_page(page)->id;
|
|
rcu_read_unlock();
|
|
|
|
if (id == wbc->wb_id) {
|
|
wbc->wb_bytes += bytes;
|
|
return;
|
|
}
|
|
|
|
if (id == wbc->wb_lcand_id)
|
|
wbc->wb_lcand_bytes += bytes;
|
|
|
|
/* Boyer-Moore majority vote algorithm */
|
|
if (!wbc->wb_tcand_bytes)
|
|
wbc->wb_tcand_id = id;
|
|
if (id == wbc->wb_tcand_id)
|
|
wbc->wb_tcand_bytes += bytes;
|
|
else
|
|
wbc->wb_tcand_bytes -= min(bytes, wbc->wb_tcand_bytes);
|
|
}
|
|
EXPORT_SYMBOL_GPL(wbc_account_io);
|
|
|
|
/**
|
|
* inode_congested - test whether an inode is congested
|
|
* @inode: inode to test for congestion (may be NULL)
|
|
* @cong_bits: mask of WB_[a]sync_congested bits to test
|
|
*
|
|
* Tests whether @inode is congested. @cong_bits is the mask of congestion
|
|
* bits to test and the return value is the mask of set bits.
|
|
*
|
|
* If cgroup writeback is enabled for @inode, the congestion state is
|
|
* determined by whether the cgwb (cgroup bdi_writeback) for the blkcg
|
|
* associated with @inode is congested; otherwise, the root wb's congestion
|
|
* state is used.
|
|
*
|
|
* @inode is allowed to be NULL as this function is often called on
|
|
* mapping->host which is NULL for the swapper space.
|
|
*/
|
|
int inode_congested(struct inode *inode, int cong_bits)
|
|
{
|
|
/*
|
|
* Once set, ->i_wb never becomes NULL while the inode is alive.
|
|
* Start transaction iff ->i_wb is visible.
|
|
*/
|
|
if (inode && inode_to_wb_is_valid(inode)) {
|
|
struct bdi_writeback *wb;
|
|
bool locked, congested;
|
|
|
|
wb = unlocked_inode_to_wb_begin(inode, &locked);
|
|
congested = wb_congested(wb, cong_bits);
|
|
unlocked_inode_to_wb_end(inode, locked);
|
|
return congested;
|
|
}
|
|
|
|
return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
|
|
}
|
|
EXPORT_SYMBOL_GPL(inode_congested);
|
|
|
|
/**
|
|
* wb_split_bdi_pages - split nr_pages to write according to bandwidth
|
|
* @wb: target bdi_writeback to split @nr_pages to
|
|
* @nr_pages: number of pages to write for the whole bdi
|
|
*
|
|
* Split @wb's portion of @nr_pages according to @wb's write bandwidth in
|
|
* relation to the total write bandwidth of all wb's w/ dirty inodes on
|
|
* @wb->bdi.
|
|
*/
|
|
static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)
|
|
{
|
|
unsigned long this_bw = wb->avg_write_bandwidth;
|
|
unsigned long tot_bw = atomic_long_read(&wb->bdi->tot_write_bandwidth);
|
|
|
|
if (nr_pages == LONG_MAX)
|
|
return LONG_MAX;
|
|
|
|
/*
|
|
* This may be called on clean wb's and proportional distribution
|
|
* may not make sense, just use the original @nr_pages in those
|
|
* cases. In general, we wanna err on the side of writing more.
|
|
*/
|
|
if (!tot_bw || this_bw >= tot_bw)
|
|
return nr_pages;
|
|
else
|
|
return DIV_ROUND_UP_ULL((u64)nr_pages * this_bw, tot_bw);
|
|
}
|
|
|
|
/**
|
|
* bdi_split_work_to_wbs - split a wb_writeback_work to all wb's of a bdi
|
|
* @bdi: target backing_dev_info
|
|
* @base_work: wb_writeback_work to issue
|
|
* @skip_if_busy: skip wb's which already have writeback in progress
|
|
*
|
|
* Split and issue @base_work to all wb's (bdi_writeback's) of @bdi which
|
|
* have dirty inodes. If @base_work->nr_page isn't %LONG_MAX, it's
|
|
* distributed to the busy wbs according to each wb's proportion in the
|
|
* total active write bandwidth of @bdi.
|
|
*/
|
|
static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
|
|
struct wb_writeback_work *base_work,
|
|
bool skip_if_busy)
|
|
{
|
|
int next_memcg_id = 0;
|
|
struct bdi_writeback *wb;
|
|
struct wb_iter iter;
|
|
|
|
might_sleep();
|
|
restart:
|
|
rcu_read_lock();
|
|
bdi_for_each_wb(wb, bdi, &iter, next_memcg_id) {
|
|
DEFINE_WB_COMPLETION_ONSTACK(fallback_work_done);
|
|
struct wb_writeback_work fallback_work;
|
|
struct wb_writeback_work *work;
|
|
long nr_pages;
|
|
|
|
/* SYNC_ALL writes out I_DIRTY_TIME too */
|
|
if (!wb_has_dirty_io(wb) &&
|
|
(base_work->sync_mode == WB_SYNC_NONE ||
|
|
list_empty(&wb->b_dirty_time)))
|
|
continue;
|
|
if (skip_if_busy && writeback_in_progress(wb))
|
|
continue;
|
|
|
|
nr_pages = wb_split_bdi_pages(wb, base_work->nr_pages);
|
|
|
|
work = kmalloc(sizeof(*work), GFP_ATOMIC);
|
|
if (work) {
|
|
*work = *base_work;
|
|
work->nr_pages = nr_pages;
|
|
work->auto_free = 1;
|
|
wb_queue_work(wb, work);
|
|
continue;
|
|
}
|
|
|
|
/* alloc failed, execute synchronously using on-stack fallback */
|
|
work = &fallback_work;
|
|
*work = *base_work;
|
|
work->nr_pages = nr_pages;
|
|
work->auto_free = 0;
|
|
work->done = &fallback_work_done;
|
|
|
|
wb_queue_work(wb, work);
|
|
|
|
next_memcg_id = wb->memcg_css->id + 1;
|
|
rcu_read_unlock();
|
|
wb_wait_for_completion(bdi, &fallback_work_done);
|
|
goto restart;
|
|
}
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
#else /* CONFIG_CGROUP_WRITEBACK */
|
|
|
|
static struct bdi_writeback *
|
|
locked_inode_to_wb_and_lock_list(struct inode *inode)
|
|
__releases(&inode->i_lock)
|
|
__acquires(&wb->list_lock)
|
|
{
|
|
struct bdi_writeback *wb = inode_to_wb(inode);
|
|
|
|
spin_unlock(&inode->i_lock);
|
|
spin_lock(&wb->list_lock);
|
|
return wb;
|
|
}
|
|
|
|
static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode)
|
|
__acquires(&wb->list_lock)
|
|
{
|
|
struct bdi_writeback *wb = inode_to_wb(inode);
|
|
|
|
spin_lock(&wb->list_lock);
|
|
return wb;
|
|
}
|
|
|
|
static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)
|
|
{
|
|
return nr_pages;
|
|
}
|
|
|
|
static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
|
|
struct wb_writeback_work *base_work,
|
|
bool skip_if_busy)
|
|
{
|
|
might_sleep();
|
|
|
|
if (!skip_if_busy || !writeback_in_progress(&bdi->wb)) {
|
|
base_work->auto_free = 0;
|
|
wb_queue_work(&bdi->wb, base_work);
|
|
}
|
|
}
|
|
|
|
#endif /* CONFIG_CGROUP_WRITEBACK */
|
|
|
|
void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
|
|
bool range_cyclic, enum wb_reason reason)
|
|
{
|
|
struct wb_writeback_work *work;
|
|
|
|
if (!wb_has_dirty_io(wb))
|
|
return;
|
|
|
|
/*
|
|
* This is WB_SYNC_NONE writeback, so if allocation fails just
|
|
* wakeup the thread for old dirty data writeback
|
|
*/
|
|
work = kzalloc(sizeof(*work), GFP_ATOMIC);
|
|
if (!work) {
|
|
trace_writeback_nowork(wb);
|
|
wb_wakeup(wb);
|
|
return;
|
|
}
|
|
|
|
work->sync_mode = WB_SYNC_NONE;
|
|
work->nr_pages = nr_pages;
|
|
work->range_cyclic = range_cyclic;
|
|
work->reason = reason;
|
|
work->auto_free = 1;
|
|
|
|
wb_queue_work(wb, work);
|
|
}
|
|
|
|
/**
|
|
* wb_start_background_writeback - start background writeback
|
|
* @wb: bdi_writback to write from
|
|
*
|
|
* Description:
|
|
* This makes sure WB_SYNC_NONE background writeback happens. When
|
|
* this function returns, it is only guaranteed that for given wb
|
|
* some IO is happening if we are over background dirty threshold.
|
|
* Caller need not hold sb s_umount semaphore.
|
|
*/
|
|
void wb_start_background_writeback(struct bdi_writeback *wb)
|
|
{
|
|
/*
|
|
* We just wake up the flusher thread. It will perform background
|
|
* writeback as soon as there is no other work to do.
|
|
*/
|
|
trace_writeback_wake_background(wb);
|
|
wb_wakeup(wb);
|
|
}
|
|
|
|
/*
|
|
* Remove the inode from the writeback list it is on.
|
|
*/
|
|
void inode_io_list_del(struct inode *inode)
|
|
{
|
|
struct bdi_writeback *wb;
|
|
|
|
wb = inode_to_wb_and_lock_list(inode);
|
|
inode_io_list_del_locked(inode, wb);
|
|
spin_unlock(&wb->list_lock);
|
|
}
|
|
|
|
/*
|
|
* Redirty an inode: set its when-it-was dirtied timestamp and move it to the
|
|
* furthest end of its superblock's dirty-inode list.
|
|
*
|
|
* Before stamping the inode's ->dirtied_when, we check to see whether it is
|
|
* already the most-recently-dirtied inode on the b_dirty list. If that is
|
|
* the case then the inode must have been redirtied while it was being written
|
|
* out and we don't reset its dirtied_when.
|
|
*/
|
|
static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
|
|
{
|
|
if (!list_empty(&wb->b_dirty)) {
|
|
struct inode *tail;
|
|
|
|
tail = wb_inode(wb->b_dirty.next);
|
|
if (time_before(inode->dirtied_when, tail->dirtied_when))
|
|
inode->dirtied_when = jiffies;
|
|
}
|
|
inode_io_list_move_locked(inode, wb, &wb->b_dirty);
|
|
}
|
|
|
|
/*
|
|
* requeue inode for re-scanning after bdi->b_io list is exhausted.
|
|
*/
|
|
static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
|
|
{
|
|
inode_io_list_move_locked(inode, wb, &wb->b_more_io);
|
|
}
|
|
|
|
static void inode_sync_complete(struct inode *inode)
|
|
{
|
|
inode->i_state &= ~I_SYNC;
|
|
/* If inode is clean an unused, put it into LRU now... */
|
|
inode_add_lru(inode);
|
|
/* Waiters must see I_SYNC cleared before being woken up */
|
|
smp_mb();
|
|
wake_up_bit(&inode->i_state, __I_SYNC);
|
|
}
|
|
|
|
static bool inode_dirtied_after(struct inode *inode, unsigned long t)
|
|
{
|
|
bool ret = time_after(inode->dirtied_when, t);
|
|
#ifndef CONFIG_64BIT
|
|
/*
|
|
* For inodes being constantly redirtied, dirtied_when can get stuck.
|
|
* It _appears_ to be in the future, but is actually in distant past.
|
|
* This test is necessary to prevent such wrapped-around relative times
|
|
* from permanently stopping the whole bdi writeback.
|
|
*/
|
|
ret = ret && time_before_eq(inode->dirtied_when, jiffies);
|
|
#endif
|
|
return ret;
|
|
}
|
|
|
|
#define EXPIRE_DIRTY_ATIME 0x0001
|
|
|
|
/*
|
|
* Move expired (dirtied before work->older_than_this) dirty inodes from
|
|
* @delaying_queue to @dispatch_queue.
|
|
*/
|
|
static int move_expired_inodes(struct list_head *delaying_queue,
|
|
struct list_head *dispatch_queue,
|
|
int flags,
|
|
struct wb_writeback_work *work)
|
|
{
|
|
unsigned long *older_than_this = NULL;
|
|
unsigned long expire_time;
|
|
LIST_HEAD(tmp);
|
|
struct list_head *pos, *node;
|
|
struct super_block *sb = NULL;
|
|
struct inode *inode;
|
|
int do_sb_sort = 0;
|
|
int moved = 0;
|
|
|
|
if ((flags & EXPIRE_DIRTY_ATIME) == 0)
|
|
older_than_this = work->older_than_this;
|
|
else if (!work->for_sync) {
|
|
expire_time = jiffies - (dirtytime_expire_interval * HZ);
|
|
older_than_this = &expire_time;
|
|
}
|
|
while (!list_empty(delaying_queue)) {
|
|
inode = wb_inode(delaying_queue->prev);
|
|
if (older_than_this &&
|
|
inode_dirtied_after(inode, *older_than_this))
|
|
break;
|
|
list_move(&inode->i_io_list, &tmp);
|
|
moved++;
|
|
if (flags & EXPIRE_DIRTY_ATIME)
|
|
set_bit(__I_DIRTY_TIME_EXPIRED, &inode->i_state);
|
|
if (sb_is_blkdev_sb(inode->i_sb))
|
|
continue;
|
|
if (sb && sb != inode->i_sb)
|
|
do_sb_sort = 1;
|
|
sb = inode->i_sb;
|
|
}
|
|
|
|
/* just one sb in list, splice to dispatch_queue and we're done */
|
|
if (!do_sb_sort) {
|
|
list_splice(&tmp, dispatch_queue);
|
|
goto out;
|
|
}
|
|
|
|
/* Move inodes from one superblock together */
|
|
while (!list_empty(&tmp)) {
|
|
sb = wb_inode(tmp.prev)->i_sb;
|
|
list_for_each_prev_safe(pos, node, &tmp) {
|
|
inode = wb_inode(pos);
|
|
if (inode->i_sb == sb)
|
|
list_move(&inode->i_io_list, dispatch_queue);
|
|
}
|
|
}
|
|
out:
|
|
return moved;
|
|
}
|
|
|
|
/*
|
|
* Queue all expired dirty inodes for io, eldest first.
|
|
* Before
|
|
* newly dirtied b_dirty b_io b_more_io
|
|
* =============> gf edc BA
|
|
* After
|
|
* newly dirtied b_dirty b_io b_more_io
|
|
* =============> g fBAedc
|
|
* |
|
|
* +--> dequeue for IO
|
|
*/
|
|
static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
|
|
{
|
|
int moved;
|
|
|
|
assert_spin_locked(&wb->list_lock);
|
|
list_splice_init(&wb->b_more_io, &wb->b_io);
|
|
moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, 0, work);
|
|
moved += move_expired_inodes(&wb->b_dirty_time, &wb->b_io,
|
|
EXPIRE_DIRTY_ATIME, work);
|
|
if (moved)
|
|
wb_io_lists_populated(wb);
|
|
trace_writeback_queue_io(wb, work, moved);
|
|
}
|
|
|
|
static int write_inode(struct inode *inode, struct writeback_control *wbc)
|
|
{
|
|
int ret;
|
|
|
|
if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) {
|
|
trace_writeback_write_inode_start(inode, wbc);
|
|
ret = inode->i_sb->s_op->write_inode(inode, wbc);
|
|
trace_writeback_write_inode(inode, wbc);
|
|
return ret;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Wait for writeback on an inode to complete. Called with i_lock held.
|
|
* Caller must make sure inode cannot go away when we drop i_lock.
|
|
*/
|
|
static void __inode_wait_for_writeback(struct inode *inode)
|
|
__releases(inode->i_lock)
|
|
__acquires(inode->i_lock)
|
|
{
|
|
DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
|
|
wait_queue_head_t *wqh;
|
|
|
|
wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
|
|
while (inode->i_state & I_SYNC) {
|
|
spin_unlock(&inode->i_lock);
|
|
__wait_on_bit(wqh, &wq, bit_wait,
|
|
TASK_UNINTERRUPTIBLE);
|
|
spin_lock(&inode->i_lock);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Wait for writeback on an inode to complete. Caller must have inode pinned.
|
|
*/
|
|
void inode_wait_for_writeback(struct inode *inode)
|
|
{
|
|
spin_lock(&inode->i_lock);
|
|
__inode_wait_for_writeback(inode);
|
|
spin_unlock(&inode->i_lock);
|
|
}
|
|
|
|
/*
|
|
* Sleep until I_SYNC is cleared. This function must be called with i_lock
|
|
* held and drops it. It is aimed for callers not holding any inode reference
|
|
* so once i_lock is dropped, inode can go away.
|
|
*/
|
|
static void inode_sleep_on_writeback(struct inode *inode)
|
|
__releases(inode->i_lock)
|
|
{
|
|
DEFINE_WAIT(wait);
|
|
wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
|
|
int sleep;
|
|
|
|
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
|
|
sleep = inode->i_state & I_SYNC;
|
|
spin_unlock(&inode->i_lock);
|
|
if (sleep)
|
|
schedule();
|
|
finish_wait(wqh, &wait);
|
|
}
|
|
|
|
/*
|
|
* Find proper writeback list for the inode depending on its current state and
|
|
* possibly also change of its state while we were doing writeback. Here we
|
|
* handle things such as livelock prevention or fairness of writeback among
|
|
* inodes. This function can be called only by flusher thread - noone else
|
|
* processes all inodes in writeback lists and requeueing inodes behind flusher
|
|
* thread's back can have unexpected consequences.
|
|
*/
|
|
static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
|
|
struct writeback_control *wbc)
|
|
{
|
|
if (inode->i_state & I_FREEING)
|
|
return;
|
|
|
|
/*
|
|
* Sync livelock prevention. Each inode is tagged and synced in one
|
|
* shot. If still dirty, it will be redirty_tail()'ed below. Update
|
|
* the dirty time to prevent enqueue and sync it again.
|
|
*/
|
|
if ((inode->i_state & I_DIRTY) &&
|
|
(wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
|
|
inode->dirtied_when = jiffies;
|
|
|
|
if (wbc->pages_skipped) {
|
|
/*
|
|
* writeback is not making progress due to locked
|
|
* buffers. Skip this inode for now.
|
|
*/
|
|
redirty_tail(inode, wb);
|
|
return;
|
|
}
|
|
|
|
if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
|
|
/*
|
|
* We didn't write back all the pages. nfs_writepages()
|
|
* sometimes bales out without doing anything.
|
|
*/
|
|
if (wbc->nr_to_write <= 0) {
|
|
/* Slice used up. Queue for next turn. */
|
|
requeue_io(inode, wb);
|
|
} else {
|
|
/*
|
|
* Writeback blocked by something other than
|
|
* congestion. Delay the inode for some time to
|
|
* avoid spinning on the CPU (100% iowait)
|
|
* retrying writeback of the dirty page/inode
|
|
* that cannot be performed immediately.
|
|
*/
|
|
redirty_tail(inode, wb);
|
|
}
|
|
} else if (inode->i_state & I_DIRTY) {
|
|
/*
|
|
* Filesystems can dirty the inode during writeback operations,
|
|
* such as delayed allocation during submission or metadata
|
|
* updates after data IO completion.
|
|
*/
|
|
redirty_tail(inode, wb);
|
|
} else if (inode->i_state & I_DIRTY_TIME) {
|
|
inode->dirtied_when = jiffies;
|
|
inode_io_list_move_locked(inode, wb, &wb->b_dirty_time);
|
|
} else {
|
|
/* The inode is clean. Remove from writeback lists. */
|
|
inode_io_list_del_locked(inode, wb);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Write out an inode and its dirty pages. Do not update the writeback list
|
|
* linkage. That is left to the caller. The caller is also responsible for
|
|
* setting I_SYNC flag and calling inode_sync_complete() to clear it.
|
|
*/
|
|
static int
|
|
__writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
|
|
{
|
|
struct address_space *mapping = inode->i_mapping;
|
|
long nr_to_write = wbc->nr_to_write;
|
|
unsigned dirty;
|
|
int ret;
|
|
|
|
WARN_ON(!(inode->i_state & I_SYNC));
|
|
|
|
trace_writeback_single_inode_start(inode, wbc, nr_to_write);
|
|
|
|
ret = do_writepages(mapping, wbc);
|
|
|
|
/*
|
|
* Make sure to wait on the data before writing out the metadata.
|
|
* This is important for filesystems that modify metadata on data
|
|
* I/O completion. We don't do it for sync(2) writeback because it has a
|
|
* separate, external IO completion path and ->sync_fs for guaranteeing
|
|
* inode metadata is written back correctly.
|
|
*/
|
|
if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync) {
|
|
int err = filemap_fdatawait(mapping);
|
|
if (ret == 0)
|
|
ret = err;
|
|
}
|
|
|
|
/*
|
|
* Some filesystems may redirty the inode during the writeback
|
|
* due to delalloc, clear dirty metadata flags right before
|
|
* write_inode()
|
|
*/
|
|
spin_lock(&inode->i_lock);
|
|
|
|
dirty = inode->i_state & I_DIRTY;
|
|
if (inode->i_state & I_DIRTY_TIME) {
|
|
if ((dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) ||
|
|
unlikely(inode->i_state & I_DIRTY_TIME_EXPIRED) ||
|
|
unlikely(time_after(jiffies,
|
|
(inode->dirtied_time_when +
|
|
dirtytime_expire_interval * HZ)))) {
|
|
dirty |= I_DIRTY_TIME | I_DIRTY_TIME_EXPIRED;
|
|
trace_writeback_lazytime(inode);
|
|
}
|
|
} else
|
|
inode->i_state &= ~I_DIRTY_TIME_EXPIRED;
|
|
inode->i_state &= ~dirty;
|
|
|
|
/*
|
|
* Paired with smp_mb() in __mark_inode_dirty(). This allows
|
|
* __mark_inode_dirty() to test i_state without grabbing i_lock -
|
|
* either they see the I_DIRTY bits cleared or we see the dirtied
|
|
* inode.
|
|
*
|
|
* I_DIRTY_PAGES is always cleared together above even if @mapping
|
|
* still has dirty pages. The flag is reinstated after smp_mb() if
|
|
* necessary. This guarantees that either __mark_inode_dirty()
|
|
* sees clear I_DIRTY_PAGES or we see PAGECACHE_TAG_DIRTY.
|
|
*/
|
|
smp_mb();
|
|
|
|
if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
|
|
inode->i_state |= I_DIRTY_PAGES;
|
|
|
|
spin_unlock(&inode->i_lock);
|
|
|
|
if (dirty & I_DIRTY_TIME)
|
|
mark_inode_dirty_sync(inode);
|
|
/* Don't write the inode if only I_DIRTY_PAGES was set */
|
|
if (dirty & ~I_DIRTY_PAGES) {
|
|
int err = write_inode(inode, wbc);
|
|
if (ret == 0)
|
|
ret = err;
|
|
}
|
|
trace_writeback_single_inode(inode, wbc, nr_to_write);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Write out an inode's dirty pages. Either the caller has an active reference
|
|
* on the inode or the inode has I_WILL_FREE set.
|
|
*
|
|
* This function is designed to be called for writing back one inode which
|
|
* we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
|
|
* and does more profound writeback list handling in writeback_sb_inodes().
|
|
*/
|
|
static int
|
|
writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
|
|
struct writeback_control *wbc)
|
|
{
|
|
int ret = 0;
|
|
|
|
spin_lock(&inode->i_lock);
|
|
if (!atomic_read(&inode->i_count))
|
|
WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
|
|
else
|
|
WARN_ON(inode->i_state & I_WILL_FREE);
|
|
|
|
if (inode->i_state & I_SYNC) {
|
|
if (wbc->sync_mode != WB_SYNC_ALL)
|
|
goto out;
|
|
/*
|
|
* It's a data-integrity sync. We must wait. Since callers hold
|
|
* inode reference or inode has I_WILL_FREE set, it cannot go
|
|
* away under us.
|
|
*/
|
|
__inode_wait_for_writeback(inode);
|
|
}
|
|
WARN_ON(inode->i_state & I_SYNC);
|
|
/*
|
|
* Skip inode if it is clean and we have no outstanding writeback in
|
|
* WB_SYNC_ALL mode. We don't want to mess with writeback lists in this
|
|
* function since flusher thread may be doing for example sync in
|
|
* parallel and if we move the inode, it could get skipped. So here we
|
|
* make sure inode is on some writeback list and leave it there unless
|
|
* we have completely cleaned the inode.
|
|
*/
|
|
if (!(inode->i_state & I_DIRTY_ALL) &&
|
|
(wbc->sync_mode != WB_SYNC_ALL ||
|
|
!mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK)))
|
|
goto out;
|
|
inode->i_state |= I_SYNC;
|
|
wbc_attach_and_unlock_inode(wbc, inode);
|
|
|
|
ret = __writeback_single_inode(inode, wbc);
|
|
|
|
wbc_detach_inode(wbc);
|
|
spin_lock(&wb->list_lock);
|
|
spin_lock(&inode->i_lock);
|
|
/*
|
|
* If inode is clean, remove it from writeback lists. Otherwise don't
|
|
* touch it. See comment above for explanation.
|
|
*/
|
|
if (!(inode->i_state & I_DIRTY_ALL))
|
|
inode_io_list_del_locked(inode, wb);
|
|
spin_unlock(&wb->list_lock);
|
|
inode_sync_complete(inode);
|
|
out:
|
|
spin_unlock(&inode->i_lock);
|
|
return ret;
|
|
}
|
|
|
|
static long writeback_chunk_size(struct bdi_writeback *wb,
|
|
struct wb_writeback_work *work)
|
|
{
|
|
long pages;
|
|
|
|
/*
|
|
* WB_SYNC_ALL mode does livelock avoidance by syncing dirty
|
|
* inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
|
|
* here avoids calling into writeback_inodes_wb() more than once.
|
|
*
|
|
* The intended call sequence for WB_SYNC_ALL writeback is:
|
|
*
|
|
* wb_writeback()
|
|
* writeback_sb_inodes() <== called only once
|
|
* write_cache_pages() <== called once for each inode
|
|
* (quickly) tag currently dirty pages
|
|
* (maybe slowly) sync all tagged pages
|
|
*/
|
|
if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
|
|
pages = LONG_MAX;
|
|
else {
|
|
pages = min(wb->avg_write_bandwidth / 2,
|
|
global_wb_domain.dirty_limit / DIRTY_SCOPE);
|
|
pages = min(pages, work->nr_pages);
|
|
pages = round_down(pages + MIN_WRITEBACK_PAGES,
|
|
MIN_WRITEBACK_PAGES);
|
|
}
|
|
|
|
return pages;
|
|
}
|
|
|
|
/*
|
|
* Write a portion of b_io inodes which belong to @sb.
|
|
*
|
|
* Return the number of pages and/or inodes written.
|
|
*
|
|
* NOTE! This is called with wb->list_lock held, and will
|
|
* unlock and relock that for each inode it ends up doing
|
|
* IO for.
|
|
*/
|
|
static long writeback_sb_inodes(struct super_block *sb,
|
|
struct bdi_writeback *wb,
|
|
struct wb_writeback_work *work)
|
|
{
|
|
struct writeback_control wbc = {
|
|
.sync_mode = work->sync_mode,
|
|
.tagged_writepages = work->tagged_writepages,
|
|
.for_kupdate = work->for_kupdate,
|
|
.for_background = work->for_background,
|
|
.for_sync = work->for_sync,
|
|
.range_cyclic = work->range_cyclic,
|
|
.range_start = 0,
|
|
.range_end = LLONG_MAX,
|
|
};
|
|
unsigned long start_time = jiffies;
|
|
long write_chunk;
|
|
long wrote = 0; /* count both pages and inodes */
|
|
|
|
while (!list_empty(&wb->b_io)) {
|
|
struct inode *inode = wb_inode(wb->b_io.prev);
|
|
|
|
if (inode->i_sb != sb) {
|
|
if (work->sb) {
|
|
/*
|
|
* We only want to write back data for this
|
|
* superblock, move all inodes not belonging
|
|
* to it back onto the dirty list.
|
|
*/
|
|
redirty_tail(inode, wb);
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* The inode belongs to a different superblock.
|
|
* Bounce back to the caller to unpin this and
|
|
* pin the next superblock.
|
|
*/
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* Don't bother with new inodes or inodes being freed, first
|
|
* kind does not need periodic writeout yet, and for the latter
|
|
* kind writeout is handled by the freer.
|
|
*/
|
|
spin_lock(&inode->i_lock);
|
|
if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
|
|
spin_unlock(&inode->i_lock);
|
|
redirty_tail(inode, wb);
|
|
continue;
|
|
}
|
|
if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
|
|
/*
|
|
* If this inode is locked for writeback and we are not
|
|
* doing writeback-for-data-integrity, move it to
|
|
* b_more_io so that writeback can proceed with the
|
|
* other inodes on s_io.
|
|
*
|
|
* We'll have another go at writing back this inode
|
|
* when we completed a full scan of b_io.
|
|
*/
|
|
spin_unlock(&inode->i_lock);
|
|
requeue_io(inode, wb);
|
|
trace_writeback_sb_inodes_requeue(inode);
|
|
continue;
|
|
}
|
|
spin_unlock(&wb->list_lock);
|
|
|
|
/*
|
|
* We already requeued the inode if it had I_SYNC set and we
|
|
* are doing WB_SYNC_NONE writeback. So this catches only the
|
|
* WB_SYNC_ALL case.
|
|
*/
|
|
if (inode->i_state & I_SYNC) {
|
|
/* Wait for I_SYNC. This function drops i_lock... */
|
|
inode_sleep_on_writeback(inode);
|
|
/* Inode may be gone, start again */
|
|
spin_lock(&wb->list_lock);
|
|
continue;
|
|
}
|
|
inode->i_state |= I_SYNC;
|
|
wbc_attach_and_unlock_inode(&wbc, inode);
|
|
|
|
write_chunk = writeback_chunk_size(wb, work);
|
|
wbc.nr_to_write = write_chunk;
|
|
wbc.pages_skipped = 0;
|
|
|
|
/*
|
|
* We use I_SYNC to pin the inode in memory. While it is set
|
|
* evict_inode() will wait so the inode cannot be freed.
|
|
*/
|
|
__writeback_single_inode(inode, &wbc);
|
|
|
|
wbc_detach_inode(&wbc);
|
|
work->nr_pages -= write_chunk - wbc.nr_to_write;
|
|
wrote += write_chunk - wbc.nr_to_write;
|
|
spin_lock(&wb->list_lock);
|
|
spin_lock(&inode->i_lock);
|
|
if (!(inode->i_state & I_DIRTY_ALL))
|
|
wrote++;
|
|
requeue_inode(inode, wb, &wbc);
|
|
inode_sync_complete(inode);
|
|
spin_unlock(&inode->i_lock);
|
|
cond_resched_lock(&wb->list_lock);
|
|
/*
|
|
* bail out to wb_writeback() often enough to check
|
|
* background threshold and other termination conditions.
|
|
*/
|
|
if (wrote) {
|
|
if (time_is_before_jiffies(start_time + HZ / 10UL))
|
|
break;
|
|
if (work->nr_pages <= 0)
|
|
break;
|
|
}
|
|
}
|
|
return wrote;
|
|
}
|
|
|
|
static long __writeback_inodes_wb(struct bdi_writeback *wb,
|
|
struct wb_writeback_work *work)
|
|
{
|
|
unsigned long start_time = jiffies;
|
|
long wrote = 0;
|
|
|
|
while (!list_empty(&wb->b_io)) {
|
|
struct inode *inode = wb_inode(wb->b_io.prev);
|
|
struct super_block *sb = inode->i_sb;
|
|
|
|
if (!trylock_super(sb)) {
|
|
/*
|
|
* trylock_super() may fail consistently due to
|
|
* s_umount being grabbed by someone else. Don't use
|
|
* requeue_io() to avoid busy retrying the inode/sb.
|
|
*/
|
|
redirty_tail(inode, wb);
|
|
continue;
|
|
}
|
|
wrote += writeback_sb_inodes(sb, wb, work);
|
|
up_read(&sb->s_umount);
|
|
|
|
/* refer to the same tests at the end of writeback_sb_inodes */
|
|
if (wrote) {
|
|
if (time_is_before_jiffies(start_time + HZ / 10UL))
|
|
break;
|
|
if (work->nr_pages <= 0)
|
|
break;
|
|
}
|
|
}
|
|
/* Leave any unwritten inodes on b_io */
|
|
return wrote;
|
|
}
|
|
|
|
static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
|
|
enum wb_reason reason)
|
|
{
|
|
struct wb_writeback_work work = {
|
|
.nr_pages = nr_pages,
|
|
.sync_mode = WB_SYNC_NONE,
|
|
.range_cyclic = 1,
|
|
.reason = reason,
|
|
};
|
|
struct blk_plug plug;
|
|
|
|
blk_start_plug(&plug);
|
|
spin_lock(&wb->list_lock);
|
|
if (list_empty(&wb->b_io))
|
|
queue_io(wb, &work);
|
|
__writeback_inodes_wb(wb, &work);
|
|
spin_unlock(&wb->list_lock);
|
|
blk_finish_plug(&plug);
|
|
|
|
return nr_pages - work.nr_pages;
|
|
}
|
|
|
|
/*
|
|
* Explicit flushing or periodic writeback of "old" data.
|
|
*
|
|
* Define "old": the first time one of an inode's pages is dirtied, we mark the
|
|
* dirtying-time in the inode's address_space. So this periodic writeback code
|
|
* just walks the superblock inode list, writing back any inodes which are
|
|
* older than a specific point in time.
|
|
*
|
|
* Try to run once per dirty_writeback_interval. But if a writeback event
|
|
* takes longer than a dirty_writeback_interval interval, then leave a
|
|
* one-second gap.
|
|
*
|
|
* older_than_this takes precedence over nr_to_write. So we'll only write back
|
|
* all dirty pages if they are all attached to "old" mappings.
|
|
*/
|
|
static long wb_writeback(struct bdi_writeback *wb,
|
|
struct wb_writeback_work *work)
|
|
{
|
|
unsigned long wb_start = jiffies;
|
|
long nr_pages = work->nr_pages;
|
|
unsigned long oldest_jif;
|
|
struct inode *inode;
|
|
long progress;
|
|
struct blk_plug plug;
|
|
|
|
oldest_jif = jiffies;
|
|
work->older_than_this = &oldest_jif;
|
|
|
|
blk_start_plug(&plug);
|
|
spin_lock(&wb->list_lock);
|
|
for (;;) {
|
|
/*
|
|
* Stop writeback when nr_pages has been consumed
|
|
*/
|
|
if (work->nr_pages <= 0)
|
|
break;
|
|
|
|
/*
|
|
* Background writeout and kupdate-style writeback may
|
|
* run forever. Stop them if there is other work to do
|
|
* so that e.g. sync can proceed. They'll be restarted
|
|
* after the other works are all done.
|
|
*/
|
|
if ((work->for_background || work->for_kupdate) &&
|
|
!list_empty(&wb->work_list))
|
|
break;
|
|
|
|
/*
|
|
* For background writeout, stop when we are below the
|
|
* background dirty threshold
|
|
*/
|
|
if (work->for_background && !wb_over_bg_thresh(wb))
|
|
break;
|
|
|
|
/*
|
|
* Kupdate and background works are special and we want to
|
|
* include all inodes that need writing. Livelock avoidance is
|
|
* handled by these works yielding to any other work so we are
|
|
* safe.
|
|
*/
|
|
if (work->for_kupdate) {
|
|
oldest_jif = jiffies -
|
|
msecs_to_jiffies(dirty_expire_interval * 10);
|
|
} else if (work->for_background)
|
|
oldest_jif = jiffies;
|
|
|
|
trace_writeback_start(wb, work);
|
|
if (list_empty(&wb->b_io))
|
|
queue_io(wb, work);
|
|
if (work->sb)
|
|
progress = writeback_sb_inodes(work->sb, wb, work);
|
|
else
|
|
progress = __writeback_inodes_wb(wb, work);
|
|
trace_writeback_written(wb, work);
|
|
|
|
wb_update_bandwidth(wb, wb_start);
|
|
|
|
/*
|
|
* Did we write something? Try for more
|
|
*
|
|
* Dirty inodes are moved to b_io for writeback in batches.
|
|
* The completion of the current batch does not necessarily
|
|
* mean the overall work is done. So we keep looping as long
|
|
* as made some progress on cleaning pages or inodes.
|
|
*/
|
|
if (progress)
|
|
continue;
|
|
/*
|
|
* No more inodes for IO, bail
|
|
*/
|
|
if (list_empty(&wb->b_more_io))
|
|
break;
|
|
/*
|
|
* Nothing written. Wait for some inode to
|
|
* become available for writeback. Otherwise
|
|
* we'll just busyloop.
|
|
*/
|
|
if (!list_empty(&wb->b_more_io)) {
|
|
trace_writeback_wait(wb, work);
|
|
inode = wb_inode(wb->b_more_io.prev);
|
|
spin_lock(&inode->i_lock);
|
|
spin_unlock(&wb->list_lock);
|
|
/* This function drops i_lock... */
|
|
inode_sleep_on_writeback(inode);
|
|
spin_lock(&wb->list_lock);
|
|
}
|
|
}
|
|
spin_unlock(&wb->list_lock);
|
|
blk_finish_plug(&plug);
|
|
|
|
return nr_pages - work->nr_pages;
|
|
}
|
|
|
|
/*
|
|
* Return the next wb_writeback_work struct that hasn't been processed yet.
|
|
*/
|
|
static struct wb_writeback_work *get_next_work_item(struct bdi_writeback *wb)
|
|
{
|
|
struct wb_writeback_work *work = NULL;
|
|
|
|
spin_lock_bh(&wb->work_lock);
|
|
if (!list_empty(&wb->work_list)) {
|
|
work = list_entry(wb->work_list.next,
|
|
struct wb_writeback_work, list);
|
|
list_del_init(&work->list);
|
|
}
|
|
spin_unlock_bh(&wb->work_lock);
|
|
return work;
|
|
}
|
|
|
|
/*
|
|
* Add in the number of potentially dirty inodes, because each inode
|
|
* write can dirty pagecache in the underlying blockdev.
|
|
*/
|
|
static unsigned long get_nr_dirty_pages(void)
|
|
{
|
|
return global_page_state(NR_FILE_DIRTY) +
|
|
global_page_state(NR_UNSTABLE_NFS) +
|
|
get_nr_dirty_inodes();
|
|
}
|
|
|
|
static long wb_check_background_flush(struct bdi_writeback *wb)
|
|
{
|
|
if (wb_over_bg_thresh(wb)) {
|
|
|
|
struct wb_writeback_work work = {
|
|
.nr_pages = LONG_MAX,
|
|
.sync_mode = WB_SYNC_NONE,
|
|
.for_background = 1,
|
|
.range_cyclic = 1,
|
|
.reason = WB_REASON_BACKGROUND,
|
|
};
|
|
|
|
return wb_writeback(wb, &work);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static long wb_check_old_data_flush(struct bdi_writeback *wb)
|
|
{
|
|
unsigned long expired;
|
|
long nr_pages;
|
|
|
|
/*
|
|
* When set to zero, disable periodic writeback
|
|
*/
|
|
if (!dirty_writeback_interval)
|
|
return 0;
|
|
|
|
expired = wb->last_old_flush +
|
|
msecs_to_jiffies(dirty_writeback_interval * 10);
|
|
if (time_before(jiffies, expired))
|
|
return 0;
|
|
|
|
wb->last_old_flush = jiffies;
|
|
nr_pages = get_nr_dirty_pages();
|
|
|
|
if (nr_pages) {
|
|
struct wb_writeback_work work = {
|
|
.nr_pages = nr_pages,
|
|
.sync_mode = WB_SYNC_NONE,
|
|
.for_kupdate = 1,
|
|
.range_cyclic = 1,
|
|
.reason = WB_REASON_PERIODIC,
|
|
};
|
|
|
|
return wb_writeback(wb, &work);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Retrieve work items and do the writeback they describe
|
|
*/
|
|
static long wb_do_writeback(struct bdi_writeback *wb)
|
|
{
|
|
struct wb_writeback_work *work;
|
|
long wrote = 0;
|
|
|
|
set_bit(WB_writeback_running, &wb->state);
|
|
while ((work = get_next_work_item(wb)) != NULL) {
|
|
struct wb_completion *done = work->done;
|
|
|
|
trace_writeback_exec(wb, work);
|
|
|
|
wrote += wb_writeback(wb, work);
|
|
|
|
if (work->auto_free)
|
|
kfree(work);
|
|
if (done && atomic_dec_and_test(&done->cnt))
|
|
wake_up_all(&wb->bdi->wb_waitq);
|
|
}
|
|
|
|
/*
|
|
* Check for periodic writeback, kupdated() style
|
|
*/
|
|
wrote += wb_check_old_data_flush(wb);
|
|
wrote += wb_check_background_flush(wb);
|
|
clear_bit(WB_writeback_running, &wb->state);
|
|
|
|
return wrote;
|
|
}
|
|
|
|
/*
|
|
* Handle writeback of dirty data for the device backed by this bdi. Also
|
|
* reschedules periodically and does kupdated style flushing.
|
|
*/
|
|
void wb_workfn(struct work_struct *work)
|
|
{
|
|
struct bdi_writeback *wb = container_of(to_delayed_work(work),
|
|
struct bdi_writeback, dwork);
|
|
long pages_written;
|
|
|
|
set_worker_desc("flush-%s", dev_name(wb->bdi->dev));
|
|
current->flags |= PF_SWAPWRITE;
|
|
|
|
if (likely(!current_is_workqueue_rescuer() ||
|
|
!test_bit(WB_registered, &wb->state))) {
|
|
/*
|
|
* The normal path. Keep writing back @wb until its
|
|
* work_list is empty. Note that this path is also taken
|
|
* if @wb is shutting down even when we're running off the
|
|
* rescuer as work_list needs to be drained.
|
|
*/
|
|
do {
|
|
pages_written = wb_do_writeback(wb);
|
|
trace_writeback_pages_written(pages_written);
|
|
} while (!list_empty(&wb->work_list));
|
|
} else {
|
|
/*
|
|
* bdi_wq can't get enough workers and we're running off
|
|
* the emergency worker. Don't hog it. Hopefully, 1024 is
|
|
* enough for efficient IO.
|
|
*/
|
|
pages_written = writeback_inodes_wb(wb, 1024,
|
|
WB_REASON_FORKER_THREAD);
|
|
trace_writeback_pages_written(pages_written);
|
|
}
|
|
|
|
if (!list_empty(&wb->work_list))
|
|
mod_delayed_work(bdi_wq, &wb->dwork, 0);
|
|
else if (wb_has_dirty_io(wb) && dirty_writeback_interval)
|
|
wb_wakeup_delayed(wb);
|
|
|
|
current->flags &= ~PF_SWAPWRITE;
|
|
}
|
|
|
|
/*
|
|
* Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
|
|
* the whole world.
|
|
*/
|
|
void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
|
|
{
|
|
struct backing_dev_info *bdi;
|
|
|
|
if (!nr_pages)
|
|
nr_pages = get_nr_dirty_pages();
|
|
|
|
rcu_read_lock();
|
|
list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
|
|
struct bdi_writeback *wb;
|
|
struct wb_iter iter;
|
|
|
|
if (!bdi_has_dirty_io(bdi))
|
|
continue;
|
|
|
|
bdi_for_each_wb(wb, bdi, &iter, 0)
|
|
wb_start_writeback(wb, wb_split_bdi_pages(wb, nr_pages),
|
|
false, reason);
|
|
}
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
/*
|
|
* Wake up bdi's periodically to make sure dirtytime inodes gets
|
|
* written back periodically. We deliberately do *not* check the
|
|
* b_dirtytime list in wb_has_dirty_io(), since this would cause the
|
|
* kernel to be constantly waking up once there are any dirtytime
|
|
* inodes on the system. So instead we define a separate delayed work
|
|
* function which gets called much more rarely. (By default, only
|
|
* once every 12 hours.)
|
|
*
|
|
* If there is any other write activity going on in the file system,
|
|
* this function won't be necessary. But if the only thing that has
|
|
* happened on the file system is a dirtytime inode caused by an atime
|
|
* update, we need this infrastructure below to make sure that inode
|
|
* eventually gets pushed out to disk.
|
|
*/
|
|
static void wakeup_dirtytime_writeback(struct work_struct *w);
|
|
static DECLARE_DELAYED_WORK(dirtytime_work, wakeup_dirtytime_writeback);
|
|
|
|
static void wakeup_dirtytime_writeback(struct work_struct *w)
|
|
{
|
|
struct backing_dev_info *bdi;
|
|
|
|
rcu_read_lock();
|
|
list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
|
|
struct bdi_writeback *wb;
|
|
struct wb_iter iter;
|
|
|
|
bdi_for_each_wb(wb, bdi, &iter, 0)
|
|
if (!list_empty(&bdi->wb.b_dirty_time))
|
|
wb_wakeup(&bdi->wb);
|
|
}
|
|
rcu_read_unlock();
|
|
schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ);
|
|
}
|
|
|
|
static int __init start_dirtytime_writeback(void)
|
|
{
|
|
schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ);
|
|
return 0;
|
|
}
|
|
__initcall(start_dirtytime_writeback);
|
|
|
|
int dirtytime_interval_handler(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp, loff_t *ppos)
|
|
{
|
|
int ret;
|
|
|
|
ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
|
|
if (ret == 0 && write)
|
|
mod_delayed_work(system_wq, &dirtytime_work, 0);
|
|
return ret;
|
|
}
|
|
|
|
static noinline void block_dump___mark_inode_dirty(struct inode *inode)
|
|
{
|
|
if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
|
|
struct dentry *dentry;
|
|
const char *name = "?";
|
|
|
|
dentry = d_find_alias(inode);
|
|
if (dentry) {
|
|
spin_lock(&dentry->d_lock);
|
|
name = (const char *) dentry->d_name.name;
|
|
}
|
|
printk(KERN_DEBUG
|
|
"%s(%d): dirtied inode %lu (%s) on %s\n",
|
|
current->comm, task_pid_nr(current), inode->i_ino,
|
|
name, inode->i_sb->s_id);
|
|
if (dentry) {
|
|
spin_unlock(&dentry->d_lock);
|
|
dput(dentry);
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* __mark_inode_dirty - internal function
|
|
* @inode: inode to mark
|
|
* @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
|
|
* Mark an inode as dirty. Callers should use mark_inode_dirty or
|
|
* mark_inode_dirty_sync.
|
|
*
|
|
* Put the inode on the super block's dirty list.
|
|
*
|
|
* CAREFUL! We mark it dirty unconditionally, but move it onto the
|
|
* dirty list only if it is hashed or if it refers to a blockdev.
|
|
* If it was not hashed, it will never be added to the dirty list
|
|
* even if it is later hashed, as it will have been marked dirty already.
|
|
*
|
|
* In short, make sure you hash any inodes _before_ you start marking
|
|
* them dirty.
|
|
*
|
|
* Note that for blockdevs, inode->dirtied_when represents the dirtying time of
|
|
* the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
|
|
* the kernel-internal blockdev inode represents the dirtying time of the
|
|
* blockdev's pages. This is why for I_DIRTY_PAGES we always use
|
|
* page->mapping->host, so the page-dirtying time is recorded in the internal
|
|
* blockdev inode.
|
|
*/
|
|
#define I_DIRTY_INODE (I_DIRTY_SYNC | I_DIRTY_DATASYNC)
|
|
void __mark_inode_dirty(struct inode *inode, int flags)
|
|
{
|
|
struct super_block *sb = inode->i_sb;
|
|
int dirtytime;
|
|
|
|
trace_writeback_mark_inode_dirty(inode, flags);
|
|
|
|
/*
|
|
* Don't do this for I_DIRTY_PAGES - that doesn't actually
|
|
* dirty the inode itself
|
|
*/
|
|
if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_TIME)) {
|
|
trace_writeback_dirty_inode_start(inode, flags);
|
|
|
|
if (sb->s_op->dirty_inode)
|
|
sb->s_op->dirty_inode(inode, flags);
|
|
|
|
trace_writeback_dirty_inode(inode, flags);
|
|
}
|
|
if (flags & I_DIRTY_INODE)
|
|
flags &= ~I_DIRTY_TIME;
|
|
dirtytime = flags & I_DIRTY_TIME;
|
|
|
|
/*
|
|
* Paired with smp_mb() in __writeback_single_inode() for the
|
|
* following lockless i_state test. See there for details.
|
|
*/
|
|
smp_mb();
|
|
|
|
if (((inode->i_state & flags) == flags) ||
|
|
(dirtytime && (inode->i_state & I_DIRTY_INODE)))
|
|
return;
|
|
|
|
if (unlikely(block_dump))
|
|
block_dump___mark_inode_dirty(inode);
|
|
|
|
spin_lock(&inode->i_lock);
|
|
if (dirtytime && (inode->i_state & I_DIRTY_INODE))
|
|
goto out_unlock_inode;
|
|
if ((inode->i_state & flags) != flags) {
|
|
const int was_dirty = inode->i_state & I_DIRTY;
|
|
|
|
inode_attach_wb(inode, NULL);
|
|
|
|
if (flags & I_DIRTY_INODE)
|
|
inode->i_state &= ~I_DIRTY_TIME;
|
|
inode->i_state |= flags;
|
|
|
|
/*
|
|
* If the inode is being synced, just update its dirty state.
|
|
* The unlocker will place the inode on the appropriate
|
|
* superblock list, based upon its state.
|
|
*/
|
|
if (inode->i_state & I_SYNC)
|
|
goto out_unlock_inode;
|
|
|
|
/*
|
|
* Only add valid (hashed) inodes to the superblock's
|
|
* dirty list. Add blockdev inodes as well.
|
|
*/
|
|
if (!S_ISBLK(inode->i_mode)) {
|
|
if (inode_unhashed(inode))
|
|
goto out_unlock_inode;
|
|
}
|
|
if (inode->i_state & I_FREEING)
|
|
goto out_unlock_inode;
|
|
|
|
/*
|
|
* If the inode was already on b_dirty/b_io/b_more_io, don't
|
|
* reposition it (that would break b_dirty time-ordering).
|
|
*/
|
|
if (!was_dirty) {
|
|
struct bdi_writeback *wb;
|
|
struct list_head *dirty_list;
|
|
bool wakeup_bdi = false;
|
|
|
|
wb = locked_inode_to_wb_and_lock_list(inode);
|
|
|
|
WARN(bdi_cap_writeback_dirty(wb->bdi) &&
|
|
!test_bit(WB_registered, &wb->state),
|
|
"bdi-%s not registered\n", wb->bdi->name);
|
|
|
|
inode->dirtied_when = jiffies;
|
|
if (dirtytime)
|
|
inode->dirtied_time_when = jiffies;
|
|
|
|
if (inode->i_state & (I_DIRTY_INODE | I_DIRTY_PAGES))
|
|
dirty_list = &wb->b_dirty;
|
|
else
|
|
dirty_list = &wb->b_dirty_time;
|
|
|
|
wakeup_bdi = inode_io_list_move_locked(inode, wb,
|
|
dirty_list);
|
|
|
|
spin_unlock(&wb->list_lock);
|
|
trace_writeback_dirty_inode_enqueue(inode);
|
|
|
|
/*
|
|
* If this is the first dirty inode for this bdi,
|
|
* we have to wake-up the corresponding bdi thread
|
|
* to make sure background write-back happens
|
|
* later.
|
|
*/
|
|
if (bdi_cap_writeback_dirty(wb->bdi) && wakeup_bdi)
|
|
wb_wakeup_delayed(wb);
|
|
return;
|
|
}
|
|
}
|
|
out_unlock_inode:
|
|
spin_unlock(&inode->i_lock);
|
|
|
|
}
|
|
EXPORT_SYMBOL(__mark_inode_dirty);
|
|
|
|
/*
|
|
* The @s_sync_lock is used to serialise concurrent sync operations
|
|
* to avoid lock contention problems with concurrent wait_sb_inodes() calls.
|
|
* Concurrent callers will block on the s_sync_lock rather than doing contending
|
|
* walks. The queueing maintains sync(2) required behaviour as all the IO that
|
|
* has been issued up to the time this function is enter is guaranteed to be
|
|
* completed by the time we have gained the lock and waited for all IO that is
|
|
* in progress regardless of the order callers are granted the lock.
|
|
*/
|
|
static void wait_sb_inodes(struct super_block *sb)
|
|
{
|
|
struct inode *inode, *old_inode = NULL;
|
|
|
|
/*
|
|
* We need to be protected against the filesystem going from
|
|
* r/o to r/w or vice versa.
|
|
*/
|
|
WARN_ON(!rwsem_is_locked(&sb->s_umount));
|
|
|
|
mutex_lock(&sb->s_sync_lock);
|
|
spin_lock(&sb->s_inode_list_lock);
|
|
|
|
/*
|
|
* Data integrity sync. Must wait for all pages under writeback,
|
|
* because there may have been pages dirtied before our sync
|
|
* call, but which had writeout started before we write it out.
|
|
* In which case, the inode may not be on the dirty list, but
|
|
* we still have to wait for that writeout.
|
|
*/
|
|
list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
|
|
struct address_space *mapping = inode->i_mapping;
|
|
|
|
spin_lock(&inode->i_lock);
|
|
if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
|
|
(mapping->nrpages == 0)) {
|
|
spin_unlock(&inode->i_lock);
|
|
continue;
|
|
}
|
|
__iget(inode);
|
|
spin_unlock(&inode->i_lock);
|
|
spin_unlock(&sb->s_inode_list_lock);
|
|
|
|
/*
|
|
* We hold a reference to 'inode' so it couldn't have been
|
|
* removed from s_inodes list while we dropped the
|
|
* s_inode_list_lock. We cannot iput the inode now as we can
|
|
* be holding the last reference and we cannot iput it under
|
|
* s_inode_list_lock. So we keep the reference and iput it
|
|
* later.
|
|
*/
|
|
iput(old_inode);
|
|
old_inode = inode;
|
|
|
|
filemap_fdatawait(mapping);
|
|
|
|
cond_resched();
|
|
|
|
spin_lock(&sb->s_inode_list_lock);
|
|
}
|
|
spin_unlock(&sb->s_inode_list_lock);
|
|
iput(old_inode);
|
|
mutex_unlock(&sb->s_sync_lock);
|
|
}
|
|
|
|
static void __writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr,
|
|
enum wb_reason reason, bool skip_if_busy)
|
|
{
|
|
DEFINE_WB_COMPLETION_ONSTACK(done);
|
|
struct wb_writeback_work work = {
|
|
.sb = sb,
|
|
.sync_mode = WB_SYNC_NONE,
|
|
.tagged_writepages = 1,
|
|
.done = &done,
|
|
.nr_pages = nr,
|
|
.reason = reason,
|
|
};
|
|
struct backing_dev_info *bdi = sb->s_bdi;
|
|
|
|
if (!bdi_has_dirty_io(bdi) || bdi == &noop_backing_dev_info)
|
|
return;
|
|
WARN_ON(!rwsem_is_locked(&sb->s_umount));
|
|
|
|
bdi_split_work_to_wbs(sb->s_bdi, &work, skip_if_busy);
|
|
wb_wait_for_completion(bdi, &done);
|
|
}
|
|
|
|
/**
|
|
* writeback_inodes_sb_nr - writeback dirty inodes from given super_block
|
|
* @sb: the superblock
|
|
* @nr: the number of pages to write
|
|
* @reason: reason why some writeback work initiated
|
|
*
|
|
* Start writeback on some inodes on this super_block. No guarantees are made
|
|
* on how many (if any) will be written, and this function does not wait
|
|
* for IO completion of submitted IO.
|
|
*/
|
|
void writeback_inodes_sb_nr(struct super_block *sb,
|
|
unsigned long nr,
|
|
enum wb_reason reason)
|
|
{
|
|
__writeback_inodes_sb_nr(sb, nr, reason, false);
|
|
}
|
|
EXPORT_SYMBOL(writeback_inodes_sb_nr);
|
|
|
|
/**
|
|
* writeback_inodes_sb - writeback dirty inodes from given super_block
|
|
* @sb: the superblock
|
|
* @reason: reason why some writeback work was initiated
|
|
*
|
|
* Start writeback on some inodes on this super_block. No guarantees are made
|
|
* on how many (if any) will be written, and this function does not wait
|
|
* for IO completion of submitted IO.
|
|
*/
|
|
void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
|
|
{
|
|
return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
|
|
}
|
|
EXPORT_SYMBOL(writeback_inodes_sb);
|
|
|
|
/**
|
|
* try_to_writeback_inodes_sb_nr - try to start writeback if none underway
|
|
* @sb: the superblock
|
|
* @nr: the number of pages to write
|
|
* @reason: the reason of writeback
|
|
*
|
|
* Invoke writeback_inodes_sb_nr if no writeback is currently underway.
|
|
* Returns 1 if writeback was started, 0 if not.
|
|
*/
|
|
bool try_to_writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr,
|
|
enum wb_reason reason)
|
|
{
|
|
if (!down_read_trylock(&sb->s_umount))
|
|
return false;
|
|
|
|
__writeback_inodes_sb_nr(sb, nr, reason, true);
|
|
up_read(&sb->s_umount);
|
|
return true;
|
|
}
|
|
EXPORT_SYMBOL(try_to_writeback_inodes_sb_nr);
|
|
|
|
/**
|
|
* try_to_writeback_inodes_sb - try to start writeback if none underway
|
|
* @sb: the superblock
|
|
* @reason: reason why some writeback work was initiated
|
|
*
|
|
* Implement by try_to_writeback_inodes_sb_nr()
|
|
* Returns 1 if writeback was started, 0 if not.
|
|
*/
|
|
bool try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
|
|
{
|
|
return try_to_writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
|
|
}
|
|
EXPORT_SYMBOL(try_to_writeback_inodes_sb);
|
|
|
|
/**
|
|
* sync_inodes_sb - sync sb inode pages
|
|
* @sb: the superblock
|
|
*
|
|
* This function writes and waits on any dirty inode belonging to this
|
|
* super_block.
|
|
*/
|
|
void sync_inodes_sb(struct super_block *sb)
|
|
{
|
|
DEFINE_WB_COMPLETION_ONSTACK(done);
|
|
struct wb_writeback_work work = {
|
|
.sb = sb,
|
|
.sync_mode = WB_SYNC_ALL,
|
|
.nr_pages = LONG_MAX,
|
|
.range_cyclic = 0,
|
|
.done = &done,
|
|
.reason = WB_REASON_SYNC,
|
|
.for_sync = 1,
|
|
};
|
|
struct backing_dev_info *bdi = sb->s_bdi;
|
|
|
|
/*
|
|
* Can't skip on !bdi_has_dirty() because we should wait for !dirty
|
|
* inodes under writeback and I_DIRTY_TIME inodes ignored by
|
|
* bdi_has_dirty() need to be written out too.
|
|
*/
|
|
if (bdi == &noop_backing_dev_info)
|
|
return;
|
|
WARN_ON(!rwsem_is_locked(&sb->s_umount));
|
|
|
|
bdi_split_work_to_wbs(bdi, &work, false);
|
|
wb_wait_for_completion(bdi, &done);
|
|
|
|
wait_sb_inodes(sb);
|
|
}
|
|
EXPORT_SYMBOL(sync_inodes_sb);
|
|
|
|
/**
|
|
* write_inode_now - write an inode to disk
|
|
* @inode: inode to write to disk
|
|
* @sync: whether the write should be synchronous or not
|
|
*
|
|
* This function commits an inode to disk immediately if it is dirty. This is
|
|
* primarily needed by knfsd.
|
|
*
|
|
* The caller must either have a ref on the inode or must have set I_WILL_FREE.
|
|
*/
|
|
int write_inode_now(struct inode *inode, int sync)
|
|
{
|
|
struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
|
|
struct writeback_control wbc = {
|
|
.nr_to_write = LONG_MAX,
|
|
.sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
|
|
.range_start = 0,
|
|
.range_end = LLONG_MAX,
|
|
};
|
|
|
|
if (!mapping_cap_writeback_dirty(inode->i_mapping))
|
|
wbc.nr_to_write = 0;
|
|
|
|
might_sleep();
|
|
return writeback_single_inode(inode, wb, &wbc);
|
|
}
|
|
EXPORT_SYMBOL(write_inode_now);
|
|
|
|
/**
|
|
* sync_inode - write an inode and its pages to disk.
|
|
* @inode: the inode to sync
|
|
* @wbc: controls the writeback mode
|
|
*
|
|
* sync_inode() will write an inode and its pages to disk. It will also
|
|
* correctly update the inode on its superblock's dirty inode lists and will
|
|
* update inode->i_state.
|
|
*
|
|
* The caller must have a ref on the inode.
|
|
*/
|
|
int sync_inode(struct inode *inode, struct writeback_control *wbc)
|
|
{
|
|
return writeback_single_inode(inode, &inode_to_bdi(inode)->wb, wbc);
|
|
}
|
|
EXPORT_SYMBOL(sync_inode);
|
|
|
|
/**
|
|
* sync_inode_metadata - write an inode to disk
|
|
* @inode: the inode to sync
|
|
* @wait: wait for I/O to complete.
|
|
*
|
|
* Write an inode to disk and adjust its dirty state after completion.
|
|
*
|
|
* Note: only writes the actual inode, no associated data or other metadata.
|
|
*/
|
|
int sync_inode_metadata(struct inode *inode, int wait)
|
|
{
|
|
struct writeback_control wbc = {
|
|
.sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
|
|
.nr_to_write = 0, /* metadata-only */
|
|
};
|
|
|
|
return sync_inode(inode, &wbc);
|
|
}
|
|
EXPORT_SYMBOL(sync_inode_metadata);
|