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 * If we're not journaling and this is a just-created file, we have to
39 * sync our parent directory (if it was freshly created) since
40 * otherwise it will only be written by writeback, leaving a huge
41 * window during which a crash may lose the file.  This may apply for
42 * the parent directory's parent as well, and so on recursively, if
43 * they are also freshly created.
44 */
45static void ext4_sync_parent(struct inode *inode)
46{
47	struct dentry *dentry = NULL;
48
49	while (inode && ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
50		ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
51		dentry = list_entry(inode->i_dentry.next,
52				    struct dentry, d_alias);
53		if (!dentry || !dentry->d_parent || !dentry->d_parent->d_inode)
54			break;
55		inode = dentry->d_parent->d_inode;
56		sync_mapping_buffers(inode->i_mapping);
57	}
58}
59
60/*
61 * akpm: A new design for ext4_sync_file().
62 *
63 * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
64 * There cannot be a transaction open by this task.
65 * Another task could have dirtied this inode.  Its data can be in any
66 * state in the journalling system.
67 *
68 * What we do is just kick off a commit and wait on it.  This will snapshot the
69 * inode to disk.
70 *
71 * i_mutex lock is held when entering and exiting this function
72 */
73
74int ext4_sync_file(struct file *file, int datasync)
75{
76	struct inode *inode = file->f_mapping->host;
77	struct ext4_inode_info *ei = EXT4_I(inode);
78	journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
79	int ret;
80	tid_t commit_tid;
81
82	J_ASSERT(ext4_journal_current_handle() == NULL);
83
84	trace_ext4_sync_file(file, datasync);
85
86	if (inode->i_sb->s_flags & MS_RDONLY)
87		return 0;
88
89	ret = flush_completed_IO(inode);
90	if (ret < 0)
91		return ret;
92
93	if (!journal) {
94		ret = generic_file_fsync(file, datasync);
95		if (!ret && !list_empty(&inode->i_dentry))
96			ext4_sync_parent(inode);
97		return ret;
98	}
99
100	/*
101	 * data=writeback,ordered:
102	 *  The caller's filemap_fdatawrite()/wait will sync the data.
103	 *  Metadata is in the journal, we wait for proper transaction to
104	 *  commit here.
105	 *
106	 * data=journal:
107	 *  filemap_fdatawrite won't do anything (the buffers are clean).
108	 *  ext4_force_commit will write the file data into the journal and
109	 *  will wait on that.
110	 *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
111	 *  (they were dirtied by commit).  But that's OK - the blocks are
112	 *  safe in-journal, which is all fsync() needs to ensure.
113	 */
114	if (ext4_should_journal_data(inode))
115		return ext4_force_commit(inode->i_sb);
116
117	commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
118	if (jbd2_log_start_commit(journal, commit_tid)) {
119		/*
120		 * When the journal is on a different device than the
121		 * fs data disk, we need to issue the barrier in
122		 * writeback mode.  (In ordered mode, the jbd2 layer
123		 * will take care of issuing the barrier.  In
124		 * data=journal, all of the data blocks are written to
125		 * the journal device.)
126		 */
127		if (ext4_should_writeback_data(inode) &&
128		    (journal->j_fs_dev != journal->j_dev) &&
129		    (journal->j_flags & JBD2_BARRIER))
130			blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL,
131					NULL, BLKDEV_IFL_WAIT);
132		ret = jbd2_log_wait_commit(journal, commit_tid);
133	} else if (journal->j_flags & JBD2_BARRIER)
134		blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL,
135			BLKDEV_IFL_WAIT);
136	return ret;
137}
138