Root/fs/ext4/fsync.c

1/*
2 * linux/fs/ext4/fsync.c
3 *
4 * Copyright (C) 1993 Stephen Tweedie (sct@redhat.com)
5 * from
6 * Copyright (C) 1992 Remy Card (card@masi.ibp.fr)
7 * Laboratoire MASI - Institut Blaise Pascal
8 * Universite Pierre et Marie Curie (Paris VI)
9 * from
10 * linux/fs/minix/truncate.c Copyright (C) 1991, 1992 Linus Torvalds
11 *
12 * ext4fs fsync primitive
13 *
14 * Big-endian to little-endian byte-swapping/bitmaps by
15 * David S. Miller (davem@caip.rutgers.edu), 1995
16 *
17 * Removed unnecessary code duplication for little endian machines
18 * and excessive __inline__s.
19 * Andi Kleen, 1997
20 *
21 * Major simplications and cleanup - we only need to do the metadata, because
22 * we can depend on generic_block_fdatasync() to sync the data blocks.
23 */
24
25#include <linux/time.h>
26#include <linux/fs.h>
27#include <linux/sched.h>
28#include <linux/writeback.h>
29#include <linux/jbd2.h>
30#include <linux/blkdev.h>
31
32#include "ext4.h"
33#include "ext4_jbd2.h"
34
35#include <trace/events/ext4.h>
36
37/*
38 * akpm: A new design for ext4_sync_file().
39 *
40 * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
41 * There cannot be a transaction open by this task.
42 * Another task could have dirtied this inode. Its data can be in any
43 * state in the journalling system.
44 *
45 * What we do is just kick off a commit and wait on it. This will snapshot the
46 * inode to disk.
47 */
48
49int ext4_sync_file(struct file *file, struct dentry *dentry, int datasync)
50{
51    struct inode *inode = dentry->d_inode;
52    journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
53    int ret = 0;
54
55    J_ASSERT(ext4_journal_current_handle() == NULL);
56
57    trace_ext4_sync_file(file, dentry, datasync);
58
59    /*
60     * data=writeback:
61     * The caller's filemap_fdatawrite()/wait will sync the data.
62     * sync_inode() will sync the metadata
63     *
64     * data=ordered:
65     * The caller's filemap_fdatawrite() will write the data and
66     * sync_inode() will write the inode if it is dirty. Then the caller's
67     * filemap_fdatawait() will wait on the pages.
68     *
69     * data=journal:
70     * filemap_fdatawrite won't do anything (the buffers are clean).
71     * ext4_force_commit will write the file data into the journal and
72     * will wait on that.
73     * filemap_fdatawait() will encounter a ton of newly-dirtied pages
74     * (they were dirtied by commit). But that's OK - the blocks are
75     * safe in-journal, which is all fsync() needs to ensure.
76     */
77    if (ext4_should_journal_data(inode)) {
78        ret = ext4_force_commit(inode->i_sb);
79        goto out;
80    }
81
82    if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
83        goto out;
84
85    /*
86     * The VFS has written the file data. If the inode is unaltered
87     * then we need not start a commit.
88     */
89    if (inode->i_state & (I_DIRTY_SYNC|I_DIRTY_DATASYNC)) {
90        struct writeback_control wbc = {
91            .sync_mode = WB_SYNC_ALL,
92            .nr_to_write = 0, /* sys_fsync did this */
93        };
94        ret = sync_inode(inode, &wbc);
95        if (journal && (journal->j_flags & JBD2_BARRIER))
96            blkdev_issue_flush(inode->i_sb->s_bdev, NULL);
97    }
98out:
99    return ret;
100}
101

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