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![Dmitry Monakhov](/assets/img/avatar_default.png)
It is ridiculous practice to scan inode block by block, this technique applicable only for old indirect files. This takes significant amount of time for really large files. Let's reuse ext4_fiemap which already traverse inode-tree in most optimal meaner. TESTCASE: ftruncate64(fd, 0); ftruncate64(fd, 1ULL << 40); /* lseek will spin very long time */ lseek64(fd, 0, SEEK_DATA); lseek64(fd, 0, SEEK_HOLE); Original report: https://lkml.org/lkml/2014/10/16/620 Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
606 lines
15 KiB
C
606 lines
15 KiB
C
/*
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* linux/fs/ext4/file.c
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*
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* Copyright (C) 1992, 1993, 1994, 1995
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* Remy Card (card@masi.ibp.fr)
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* Laboratoire MASI - Institut Blaise Pascal
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* Universite Pierre et Marie Curie (Paris VI)
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*
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* from
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*
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* linux/fs/minix/file.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*
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* ext4 fs regular file handling primitives
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*
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* 64-bit file support on 64-bit platforms by Jakub Jelinek
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* (jj@sunsite.ms.mff.cuni.cz)
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*/
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#include <linux/time.h>
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#include <linux/fs.h>
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#include <linux/jbd2.h>
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#include <linux/mount.h>
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#include <linux/path.h>
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#include <linux/aio.h>
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#include <linux/quotaops.h>
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#include <linux/pagevec.h>
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#include "ext4.h"
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#include "ext4_jbd2.h"
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#include "xattr.h"
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#include "acl.h"
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/*
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* Called when an inode is released. Note that this is different
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* from ext4_file_open: open gets called at every open, but release
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* gets called only when /all/ the files are closed.
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*/
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static int ext4_release_file(struct inode *inode, struct file *filp)
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{
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if (ext4_test_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE)) {
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ext4_alloc_da_blocks(inode);
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ext4_clear_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE);
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}
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/* if we are the last writer on the inode, drop the block reservation */
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if ((filp->f_mode & FMODE_WRITE) &&
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(atomic_read(&inode->i_writecount) == 1) &&
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!EXT4_I(inode)->i_reserved_data_blocks)
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{
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down_write(&EXT4_I(inode)->i_data_sem);
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ext4_discard_preallocations(inode);
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up_write(&EXT4_I(inode)->i_data_sem);
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}
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if (is_dx(inode) && filp->private_data)
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ext4_htree_free_dir_info(filp->private_data);
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return 0;
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}
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static void ext4_unwritten_wait(struct inode *inode)
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{
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wait_queue_head_t *wq = ext4_ioend_wq(inode);
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wait_event(*wq, (atomic_read(&EXT4_I(inode)->i_unwritten) == 0));
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}
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/*
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* This tests whether the IO in question is block-aligned or not.
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* Ext4 utilizes unwritten extents when hole-filling during direct IO, and they
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* are converted to written only after the IO is complete. Until they are
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* mapped, these blocks appear as holes, so dio_zero_block() will assume that
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* it needs to zero out portions of the start and/or end block. If 2 AIO
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* threads are at work on the same unwritten block, they must be synchronized
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* or one thread will zero the other's data, causing corruption.
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*/
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static int
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ext4_unaligned_aio(struct inode *inode, struct iov_iter *from, loff_t pos)
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{
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struct super_block *sb = inode->i_sb;
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int blockmask = sb->s_blocksize - 1;
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if (pos >= i_size_read(inode))
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return 0;
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if ((pos | iov_iter_alignment(from)) & blockmask)
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return 1;
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return 0;
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}
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static ssize_t
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ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
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{
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struct file *file = iocb->ki_filp;
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struct inode *inode = file_inode(iocb->ki_filp);
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struct mutex *aio_mutex = NULL;
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struct blk_plug plug;
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int o_direct = file->f_flags & O_DIRECT;
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int overwrite = 0;
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size_t length = iov_iter_count(from);
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ssize_t ret;
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loff_t pos = iocb->ki_pos;
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/*
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* Unaligned direct AIO must be serialized; see comment above
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* In the case of O_APPEND, assume that we must always serialize
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*/
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if (o_direct &&
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ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) &&
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!is_sync_kiocb(iocb) &&
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(file->f_flags & O_APPEND ||
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ext4_unaligned_aio(inode, from, pos))) {
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aio_mutex = ext4_aio_mutex(inode);
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mutex_lock(aio_mutex);
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ext4_unwritten_wait(inode);
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}
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mutex_lock(&inode->i_mutex);
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if (file->f_flags & O_APPEND)
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iocb->ki_pos = pos = i_size_read(inode);
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/*
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* If we have encountered a bitmap-format file, the size limit
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* is smaller than s_maxbytes, which is for extent-mapped files.
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*/
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if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
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struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
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if ((pos > sbi->s_bitmap_maxbytes) ||
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(pos == sbi->s_bitmap_maxbytes && length > 0)) {
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mutex_unlock(&inode->i_mutex);
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ret = -EFBIG;
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goto errout;
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}
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if (pos + length > sbi->s_bitmap_maxbytes)
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iov_iter_truncate(from, sbi->s_bitmap_maxbytes - pos);
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}
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iocb->private = &overwrite;
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if (o_direct) {
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blk_start_plug(&plug);
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/* check whether we do a DIO overwrite or not */
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if (ext4_should_dioread_nolock(inode) && !aio_mutex &&
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!file->f_mapping->nrpages && pos + length <= i_size_read(inode)) {
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struct ext4_map_blocks map;
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unsigned int blkbits = inode->i_blkbits;
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int err, len;
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map.m_lblk = pos >> blkbits;
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map.m_len = (EXT4_BLOCK_ALIGN(pos + length, blkbits) >> blkbits)
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- map.m_lblk;
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len = map.m_len;
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err = ext4_map_blocks(NULL, inode, &map, 0);
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/*
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* 'err==len' means that all of blocks has
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* been preallocated no matter they are
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* initialized or not. For excluding
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* unwritten extents, we need to check
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* m_flags. There are two conditions that
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* indicate for initialized extents. 1) If we
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* hit extent cache, EXT4_MAP_MAPPED flag is
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* returned; 2) If we do a real lookup,
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* non-flags are returned. So we should check
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* these two conditions.
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*/
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if (err == len && (map.m_flags & EXT4_MAP_MAPPED))
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overwrite = 1;
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}
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}
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ret = __generic_file_write_iter(iocb, from);
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mutex_unlock(&inode->i_mutex);
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if (ret > 0) {
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ssize_t err;
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err = generic_write_sync(file, iocb->ki_pos - ret, ret);
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if (err < 0)
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ret = err;
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}
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if (o_direct)
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blk_finish_plug(&plug);
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errout:
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if (aio_mutex)
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mutex_unlock(aio_mutex);
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return ret;
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}
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static const struct vm_operations_struct ext4_file_vm_ops = {
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.fault = filemap_fault,
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.map_pages = filemap_map_pages,
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.page_mkwrite = ext4_page_mkwrite,
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.remap_pages = generic_file_remap_pages,
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};
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static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
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{
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file_accessed(file);
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vma->vm_ops = &ext4_file_vm_ops;
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return 0;
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}
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static int ext4_file_open(struct inode * inode, struct file * filp)
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{
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struct super_block *sb = inode->i_sb;
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struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
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struct vfsmount *mnt = filp->f_path.mnt;
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struct path path;
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char buf[64], *cp;
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if (unlikely(!(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED) &&
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!(sb->s_flags & MS_RDONLY))) {
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sbi->s_mount_flags |= EXT4_MF_MNTDIR_SAMPLED;
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/*
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* Sample where the filesystem has been mounted and
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* store it in the superblock for sysadmin convenience
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* when trying to sort through large numbers of block
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* devices or filesystem images.
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*/
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memset(buf, 0, sizeof(buf));
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path.mnt = mnt;
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path.dentry = mnt->mnt_root;
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cp = d_path(&path, buf, sizeof(buf));
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if (!IS_ERR(cp)) {
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handle_t *handle;
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int err;
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handle = ext4_journal_start_sb(sb, EXT4_HT_MISC, 1);
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if (IS_ERR(handle))
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return PTR_ERR(handle);
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BUFFER_TRACE(sbi->s_sbh, "get_write_access");
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err = ext4_journal_get_write_access(handle, sbi->s_sbh);
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if (err) {
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ext4_journal_stop(handle);
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return err;
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}
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strlcpy(sbi->s_es->s_last_mounted, cp,
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sizeof(sbi->s_es->s_last_mounted));
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ext4_handle_dirty_super(handle, sb);
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ext4_journal_stop(handle);
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}
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}
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/*
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* Set up the jbd2_inode if we are opening the inode for
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* writing and the journal is present
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*/
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if (filp->f_mode & FMODE_WRITE) {
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int ret = ext4_inode_attach_jinode(inode);
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if (ret < 0)
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return ret;
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}
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return dquot_file_open(inode, filp);
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}
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/*
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* Here we use ext4_map_blocks() to get a block mapping for a extent-based
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* file rather than ext4_ext_walk_space() because we can introduce
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* SEEK_DATA/SEEK_HOLE for block-mapped and extent-mapped file at the same
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* function. When extent status tree has been fully implemented, it will
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* track all extent status for a file and we can directly use it to
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* retrieve the offset for SEEK_DATA/SEEK_HOLE.
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*/
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/*
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* When we retrieve the offset for SEEK_DATA/SEEK_HOLE, we would need to
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* lookup page cache to check whether or not there has some data between
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* [startoff, endoff] because, if this range contains an unwritten extent,
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* we determine this extent as a data or a hole according to whether the
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* page cache has data or not.
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*/
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static int ext4_find_unwritten_pgoff(struct inode *inode, int whence,
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loff_t endoff, loff_t *offset)
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{
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struct pagevec pvec;
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pgoff_t index;
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pgoff_t end;
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loff_t startoff;
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loff_t lastoff;
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int found = 0;
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startoff = *offset;
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lastoff = startoff;
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index = startoff >> PAGE_CACHE_SHIFT;
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end = endoff >> PAGE_CACHE_SHIFT;
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pagevec_init(&pvec, 0);
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do {
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int i, num;
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unsigned long nr_pages;
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num = min_t(pgoff_t, end - index, PAGEVEC_SIZE);
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nr_pages = pagevec_lookup(&pvec, inode->i_mapping, index,
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(pgoff_t)num);
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if (nr_pages == 0) {
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if (whence == SEEK_DATA)
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break;
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BUG_ON(whence != SEEK_HOLE);
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/*
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* If this is the first time to go into the loop and
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* offset is not beyond the end offset, it will be a
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* hole at this offset
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*/
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if (lastoff == startoff || lastoff < endoff)
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found = 1;
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break;
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}
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/*
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* If this is the first time to go into the loop and
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* offset is smaller than the first page offset, it will be a
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* hole at this offset.
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*/
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if (lastoff == startoff && whence == SEEK_HOLE &&
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lastoff < page_offset(pvec.pages[0])) {
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found = 1;
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break;
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}
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for (i = 0; i < nr_pages; i++) {
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struct page *page = pvec.pages[i];
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struct buffer_head *bh, *head;
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/*
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* If the current offset is not beyond the end of given
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* range, it will be a hole.
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*/
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if (lastoff < endoff && whence == SEEK_HOLE &&
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page->index > end) {
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found = 1;
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*offset = lastoff;
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goto out;
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}
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lock_page(page);
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if (unlikely(page->mapping != inode->i_mapping)) {
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unlock_page(page);
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continue;
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}
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if (!page_has_buffers(page)) {
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unlock_page(page);
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continue;
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}
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if (page_has_buffers(page)) {
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lastoff = page_offset(page);
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bh = head = page_buffers(page);
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do {
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if (buffer_uptodate(bh) ||
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buffer_unwritten(bh)) {
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if (whence == SEEK_DATA)
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found = 1;
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} else {
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if (whence == SEEK_HOLE)
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found = 1;
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}
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if (found) {
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*offset = max_t(loff_t,
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startoff, lastoff);
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unlock_page(page);
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goto out;
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}
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lastoff += bh->b_size;
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bh = bh->b_this_page;
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} while (bh != head);
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}
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lastoff = page_offset(page) + PAGE_SIZE;
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unlock_page(page);
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}
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/*
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* The no. of pages is less than our desired, that would be a
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* hole in there.
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*/
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if (nr_pages < num && whence == SEEK_HOLE) {
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found = 1;
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*offset = lastoff;
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break;
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}
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index = pvec.pages[i - 1]->index + 1;
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pagevec_release(&pvec);
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} while (index <= end);
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out:
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pagevec_release(&pvec);
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return found;
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}
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/*
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* ext4_seek_data() retrieves the offset for SEEK_DATA.
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*/
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static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
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{
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struct inode *inode = file->f_mapping->host;
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struct fiemap_extent_info fie;
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struct fiemap_extent ext[2];
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loff_t next;
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int i, ret = 0;
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mutex_lock(&inode->i_mutex);
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if (offset >= inode->i_size) {
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mutex_unlock(&inode->i_mutex);
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return -ENXIO;
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}
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fie.fi_flags = 0;
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fie.fi_extents_max = 2;
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fie.fi_extents_start = (struct fiemap_extent __user *) &ext;
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while (1) {
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mm_segment_t old_fs = get_fs();
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fie.fi_extents_mapped = 0;
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memset(ext, 0, sizeof(*ext) * fie.fi_extents_max);
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set_fs(get_ds());
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ret = ext4_fiemap(inode, &fie, offset, maxsize - offset);
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set_fs(old_fs);
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if (ret)
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break;
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/* No extents found, EOF */
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if (!fie.fi_extents_mapped) {
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ret = -ENXIO;
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break;
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}
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for (i = 0; i < fie.fi_extents_mapped; i++) {
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next = (loff_t)(ext[i].fe_length + ext[i].fe_logical);
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if (offset < (loff_t)ext[i].fe_logical)
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offset = (loff_t)ext[i].fe_logical;
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/*
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* If extent is not unwritten, then it contains valid
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* data, mapped or delayed.
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*/
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if (!(ext[i].fe_flags & FIEMAP_EXTENT_UNWRITTEN))
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goto out;
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/*
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* If there is a unwritten extent at this offset,
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* it will be as a data or a hole according to page
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* cache that has data or not.
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*/
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if (ext4_find_unwritten_pgoff(inode, SEEK_DATA,
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next, &offset))
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goto out;
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if (ext[i].fe_flags & FIEMAP_EXTENT_LAST) {
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ret = -ENXIO;
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goto out;
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}
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offset = next;
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}
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}
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if (offset > inode->i_size)
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offset = inode->i_size;
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out:
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mutex_unlock(&inode->i_mutex);
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if (ret)
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return ret;
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return vfs_setpos(file, offset, maxsize);
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}
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/*
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* ext4_seek_hole() retrieves the offset for SEEK_HOLE
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*/
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static loff_t ext4_seek_hole(struct file *file, loff_t offset, loff_t maxsize)
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{
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struct inode *inode = file->f_mapping->host;
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struct fiemap_extent_info fie;
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struct fiemap_extent ext[2];
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loff_t next;
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int i, ret = 0;
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mutex_lock(&inode->i_mutex);
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if (offset >= inode->i_size) {
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mutex_unlock(&inode->i_mutex);
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return -ENXIO;
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}
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fie.fi_flags = 0;
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fie.fi_extents_max = 2;
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fie.fi_extents_start = (struct fiemap_extent __user *)&ext;
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while (1) {
|
|
mm_segment_t old_fs = get_fs();
|
|
|
|
fie.fi_extents_mapped = 0;
|
|
memset(ext, 0, sizeof(*ext));
|
|
|
|
set_fs(get_ds());
|
|
ret = ext4_fiemap(inode, &fie, offset, maxsize - offset);
|
|
set_fs(old_fs);
|
|
if (ret)
|
|
break;
|
|
|
|
/* No extents found */
|
|
if (!fie.fi_extents_mapped)
|
|
break;
|
|
|
|
for (i = 0; i < fie.fi_extents_mapped; i++) {
|
|
next = (loff_t)(ext[i].fe_logical + ext[i].fe_length);
|
|
/*
|
|
* If extent is not unwritten, then it contains valid
|
|
* data, mapped or delayed.
|
|
*/
|
|
if (!(ext[i].fe_flags & FIEMAP_EXTENT_UNWRITTEN)) {
|
|
if (offset < (loff_t)ext[i].fe_logical)
|
|
goto out;
|
|
offset = next;
|
|
continue;
|
|
}
|
|
/*
|
|
* If there is a unwritten extent at this offset,
|
|
* it will be as a data or a hole according to page
|
|
* cache that has data or not.
|
|
*/
|
|
if (ext4_find_unwritten_pgoff(inode, SEEK_HOLE,
|
|
next, &offset))
|
|
goto out;
|
|
|
|
offset = next;
|
|
if (ext[i].fe_flags & FIEMAP_EXTENT_LAST)
|
|
goto out;
|
|
}
|
|
}
|
|
if (offset > inode->i_size)
|
|
offset = inode->i_size;
|
|
out:
|
|
mutex_unlock(&inode->i_mutex);
|
|
if (ret)
|
|
return ret;
|
|
|
|
return vfs_setpos(file, offset, maxsize);
|
|
}
|
|
|
|
/*
|
|
* ext4_llseek() handles both block-mapped and extent-mapped maxbytes values
|
|
* by calling generic_file_llseek_size() with the appropriate maxbytes
|
|
* value for each.
|
|
*/
|
|
loff_t ext4_llseek(struct file *file, loff_t offset, int whence)
|
|
{
|
|
struct inode *inode = file->f_mapping->host;
|
|
loff_t maxbytes;
|
|
|
|
if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
|
|
maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes;
|
|
else
|
|
maxbytes = inode->i_sb->s_maxbytes;
|
|
|
|
switch (whence) {
|
|
case SEEK_SET:
|
|
case SEEK_CUR:
|
|
case SEEK_END:
|
|
return generic_file_llseek_size(file, offset, whence,
|
|
maxbytes, i_size_read(inode));
|
|
case SEEK_DATA:
|
|
return ext4_seek_data(file, offset, maxbytes);
|
|
case SEEK_HOLE:
|
|
return ext4_seek_hole(file, offset, maxbytes);
|
|
}
|
|
|
|
return -EINVAL;
|
|
}
|
|
|
|
const struct file_operations ext4_file_operations = {
|
|
.llseek = ext4_llseek,
|
|
.read = new_sync_read,
|
|
.write = new_sync_write,
|
|
.read_iter = generic_file_read_iter,
|
|
.write_iter = ext4_file_write_iter,
|
|
.unlocked_ioctl = ext4_ioctl,
|
|
#ifdef CONFIG_COMPAT
|
|
.compat_ioctl = ext4_compat_ioctl,
|
|
#endif
|
|
.mmap = ext4_file_mmap,
|
|
.open = ext4_file_open,
|
|
.release = ext4_release_file,
|
|
.fsync = ext4_sync_file,
|
|
.splice_read = generic_file_splice_read,
|
|
.splice_write = iter_file_splice_write,
|
|
.fallocate = ext4_fallocate,
|
|
};
|
|
|
|
const struct inode_operations ext4_file_inode_operations = {
|
|
.setattr = ext4_setattr,
|
|
.getattr = ext4_getattr,
|
|
.setxattr = generic_setxattr,
|
|
.getxattr = generic_getxattr,
|
|
.listxattr = ext4_listxattr,
|
|
.removexattr = generic_removexattr,
|
|
.get_acl = ext4_get_acl,
|
|
.set_acl = ext4_set_acl,
|
|
.fiemap = ext4_fiemap,
|
|
};
|
|
|