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/blkdev.h>
30
31#include "ext4.h"
32#include "ext4_jbd2.h"
33
34#include <trace/events/ext4.h>
35
36/*
37 * If we're not journaling and this is a just-created file, we have to
38 * sync our parent directory (if it was freshly created) since
39 * otherwise it will only be written by writeback, leaving a huge
40 * window during which a crash may lose the file.  This may apply for
41 * the parent directory's parent as well, and so on recursively, if
42 * they are also freshly created.
43 */
44static int ext4_sync_parent(struct inode *inode)
45{
46	struct dentry *dentry = NULL;
47	struct inode *next;
48	int ret = 0;
49
50	if (!ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY))
51		return 0;
52	inode = igrab(inode);
53	while (ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
54		ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
55		dentry = d_find_any_alias(inode);
56		if (!dentry)
57			break;
58		next = igrab(d_inode(dentry->d_parent));
59		dput(dentry);
60		if (!next)
61			break;
62		iput(inode);
63		inode = next;
64		ret = sync_mapping_buffers(inode->i_mapping);
65		if (ret)
66			break;
67		ret = sync_inode_metadata(inode, 1);
68		if (ret)
69			break;
70	}
71	iput(inode);
72	return ret;
73}
74
75/*
76 * akpm: A new design for ext4_sync_file().
77 *
78 * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
79 * There cannot be a transaction open by this task.
80 * Another task could have dirtied this inode.  Its data can be in any
81 * state in the journalling system.
82 *
83 * What we do is just kick off a commit and wait on it.  This will snapshot the
84 * inode to disk.
85 */
86
87int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
88{
89	struct inode *inode = file->f_mapping->host;
90	struct ext4_inode_info *ei = EXT4_I(inode);
91	journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
92	int ret = 0, err;
93	tid_t commit_tid;
94	bool needs_barrier = false;
95
96	J_ASSERT(ext4_journal_current_handle() == NULL);
97
98	trace_ext4_sync_file_enter(file, datasync);
99
100	if (inode->i_sb->s_flags & MS_RDONLY) {
101		/* Make sure that we read updated s_mount_flags value */
102		smp_rmb();
103		if (EXT4_SB(inode->i_sb)->s_mount_flags & EXT4_MF_FS_ABORTED)
104			ret = -EROFS;
105		goto out;
106	}
107
108	if (!journal) {
109		ret = generic_file_fsync(file, start, end, datasync);
110		if (!ret && !hlist_empty(&inode->i_dentry))
111			ret = ext4_sync_parent(inode);
112		goto out;
113	}
114
115	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
116	if (ret)
117		return ret;
118	/*
119	 * data=writeback,ordered:
120	 *  The caller's filemap_fdatawrite()/wait will sync the data.
121	 *  Metadata is in the journal, we wait for proper transaction to
122	 *  commit here.
123	 *
124	 * data=journal:
125	 *  filemap_fdatawrite won't do anything (the buffers are clean).
126	 *  ext4_force_commit will write the file data into the journal and
127	 *  will wait on that.
128	 *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
129	 *  (they were dirtied by commit).  But that's OK - the blocks are
130	 *  safe in-journal, which is all fsync() needs to ensure.
131	 */
132	if (ext4_should_journal_data(inode)) {
133		ret = ext4_force_commit(inode->i_sb);
134		goto out;
135	}
136
137	commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
138	if (journal->j_flags & JBD2_BARRIER &&
139	    !jbd2_trans_will_send_data_barrier(journal, commit_tid))
140		needs_barrier = true;
141	ret = jbd2_complete_transaction(journal, commit_tid);
142	if (needs_barrier) {
143		err = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
144		if (!ret)
145			ret = err;
146	}
147out:
148	trace_ext4_sync_file_exit(inode, ret);
149	return ret;
150}
151