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5f3481e9a8
We need to flush the write cache unconditionally in ->fsync, otherwise writes into already allocated blocks can get lost. Writes into fully allocated files are very common when using disk images for virtualization, and without this fix can easily lose data after an fdatasync, which is the typical implementation for a cache flush on the virtual drive. Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Eric Sandeen <sandeen@redhat.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
100 lines
3 KiB
C
100 lines
3 KiB
C
/*
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* linux/fs/ext4/fsync.c
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*
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* Copyright (C) 1993 Stephen Tweedie (sct@redhat.com)
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* from
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* Copyright (C) 1992 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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* from
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* linux/fs/minix/truncate.c Copyright (C) 1991, 1992 Linus Torvalds
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*
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* ext4fs fsync primitive
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*
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* Big-endian to little-endian byte-swapping/bitmaps by
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* David S. Miller (davem@caip.rutgers.edu), 1995
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*
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* Removed unnecessary code duplication for little endian machines
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* and excessive __inline__s.
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* Andi Kleen, 1997
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*
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* Major simplications and cleanup - we only need to do the metadata, because
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* we can depend on generic_block_fdatasync() to sync the data blocks.
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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/sched.h>
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#include <linux/writeback.h>
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#include <linux/jbd2.h>
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#include <linux/blkdev.h>
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#include "ext4.h"
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#include "ext4_jbd2.h"
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#include <trace/events/ext4.h>
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/*
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* akpm: A new design for ext4_sync_file().
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*
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* This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
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* There cannot be a transaction open by this task.
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* Another task could have dirtied this inode. Its data can be in any
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* state in the journalling system.
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*
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* What we do is just kick off a commit and wait on it. This will snapshot the
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* inode to disk.
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*/
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int ext4_sync_file(struct file *file, struct dentry *dentry, int datasync)
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{
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struct inode *inode = dentry->d_inode;
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journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
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int ret = 0;
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J_ASSERT(ext4_journal_current_handle() == NULL);
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trace_ext4_sync_file(file, dentry, datasync);
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/*
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* data=writeback:
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* The caller's filemap_fdatawrite()/wait will sync the data.
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* sync_inode() will sync the metadata
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*
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* data=ordered:
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* The caller's filemap_fdatawrite() will write the data and
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* sync_inode() will write the inode if it is dirty. Then the caller's
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* filemap_fdatawait() will wait on the pages.
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*
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* data=journal:
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* filemap_fdatawrite won't do anything (the buffers are clean).
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* ext4_force_commit will write the file data into the journal and
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* will wait on that.
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* filemap_fdatawait() will encounter a ton of newly-dirtied pages
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* (they were dirtied by commit). But that's OK - the blocks are
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* safe in-journal, which is all fsync() needs to ensure.
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*/
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if (ext4_should_journal_data(inode)) {
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ret = ext4_force_commit(inode->i_sb);
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goto out;
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}
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if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
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goto out;
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/*
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* The VFS has written the file data. If the inode is unaltered
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* then we need not start a commit.
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*/
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if (inode->i_state & (I_DIRTY_SYNC|I_DIRTY_DATASYNC)) {
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struct writeback_control wbc = {
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.sync_mode = WB_SYNC_ALL,
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.nr_to_write = 0, /* sys_fsync did this */
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};
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ret = sync_inode(inode, &wbc);
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}
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out:
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if (journal && (journal->j_flags & JBD2_BARRIER))
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blkdev_issue_flush(inode->i_sb->s_bdev, NULL);
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return ret;
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}
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