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fsync.c
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1 /*
2  * linux/fs/ext3/fsync.c
3  *
4  * Copyright (C) 1993 Stephen Tweedie ([email protected])
5  * from
6  * Copyright (C) 1992 Remy Card ([email protected])
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  * ext3fs fsync primitive
13  *
14  * Big-endian to little-endian byte-swapping/bitmaps by
15  * David S. Miller ([email protected]), 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/blkdev.h>
26 #include <linux/writeback.h>
27 #include "ext3.h"
28 
29 /*
30  * akpm: A new design for ext3_sync_file().
31  *
32  * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
33  * There cannot be a transaction open by this task.
34  * Another task could have dirtied this inode. Its data can be in any
35  * state in the journalling system.
36  *
37  * What we do is just kick off a commit and wait on it. This will snapshot the
38  * inode to disk.
39  */
40 
41 int ext3_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
42 {
43  struct inode *inode = file->f_mapping->host;
44  struct ext3_inode_info *ei = EXT3_I(inode);
45  journal_t *journal = EXT3_SB(inode->i_sb)->s_journal;
46  int ret, needs_barrier = 0;
47  tid_t commit_tid;
48 
49  trace_ext3_sync_file_enter(file, datasync);
50 
51  if (inode->i_sb->s_flags & MS_RDONLY)
52  return 0;
53 
54  ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
55  if (ret)
56  goto out;
57 
58  J_ASSERT(ext3_journal_current_handle() == NULL);
59 
60  /*
61  * data=writeback,ordered:
62  * The caller's filemap_fdatawrite()/wait will sync the data.
63  * Metadata is in the journal, we wait for a proper transaction
64  * to commit here.
65  *
66  * data=journal:
67  * filemap_fdatawrite won't do anything (the buffers are clean).
68  * ext3_force_commit will write the file data into the journal and
69  * will wait on that.
70  * filemap_fdatawait() will encounter a ton of newly-dirtied pages
71  * (they were dirtied by commit). But that's OK - the blocks are
72  * safe in-journal, which is all fsync() needs to ensure.
73  */
74  if (ext3_should_journal_data(inode)) {
75  ret = ext3_force_commit(inode->i_sb);
76  goto out;
77  }
78 
79  if (datasync)
80  commit_tid = atomic_read(&ei->i_datasync_tid);
81  else
82  commit_tid = atomic_read(&ei->i_sync_tid);
83 
84  if (test_opt(inode->i_sb, BARRIER) &&
85  !journal_trans_will_send_data_barrier(journal, commit_tid))
86  needs_barrier = 1;
87  log_start_commit(journal, commit_tid);
88  ret = log_wait_commit(journal, commit_tid);
89 
90  /*
91  * In case we didn't commit a transaction, we have to flush
92  * disk caches manually so that data really is on persistent
93  * storage
94  */
95  if (needs_barrier) {
96  int err;
97 
98  err = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
99  if (!ret)
100  ret = err;
101  }
102 out:
103  trace_ext3_sync_file_exit(inode, ret);
104  return ret;
105 }