1// SPDX-License-Identifier: GPL-2.0
2/*
3 *  linux/fs/ext4/fsync.c
4 *
5 *  Copyright (C) 1993  Stephen Tweedie (sct@redhat.com)
6 *  from
7 *  Copyright (C) 1992  Remy Card (card@masi.ibp.fr)
8 *                      Laboratoire MASI - Institut Blaise Pascal
9 *                      Universite Pierre et Marie Curie (Paris VI)
10 *  from
11 *  linux/fs/minix/truncate.c   Copyright (C) 1991, 1992  Linus Torvalds
12 *
13 *  ext4fs fsync primitive
14 *
15 *  Big-endian to little-endian byte-swapping/bitmaps by
16 *        David S. Miller (davem@caip.rutgers.edu), 1995
17 *
18 *  Removed unnecessary code duplication for little endian machines
19 *  and excessive __inline__s.
20 *        Andi Kleen, 1997
21 *
22 * Major simplications and cleanup - we only need to do the metadata, because
23 * we can depend on generic_block_fdatasync() to sync the data blocks.
24 */
25
26#include <linux/time.h>
27#include <linux/fs.h>
28#include <linux/sched.h>
29#include <linux/writeback.h>
30#include <linux/blkdev.h>
31#include <linux/buffer_head.h>
32
33#include "ext4.h"
34#include "ext4_jbd2.h"
35
36#include <trace/events/ext4.h>
37
38/*
39 * If we're not journaling and this is a just-created file, we have to
40 * sync our parent directory (if it was freshly created) since
41 * otherwise it will only be written by writeback, leaving a huge
42 * window during which a crash may lose the file.  This may apply for
43 * the parent directory's parent as well, and so on recursively, if
44 * they are also freshly created.
45 */
46static int ext4_sync_parent(struct inode *inode)
47{
48	struct dentry *dentry, *next;
49	int ret = 0;
50
51	if (!ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY))
52		return 0;
53	dentry = d_find_any_alias(inode);
54	if (!dentry)
55		return 0;
56	while (ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
57		ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
58
59		next = dget_parent(dentry);
60		dput(dentry);
61		dentry = next;
62		inode = dentry->d_inode;
63
64		/*
65		 * The directory inode may have gone through rmdir by now. But
66		 * the inode itself and its blocks are still allocated (we hold
67		 * a reference to the inode via its dentry), so it didn't go
68		 * through ext4_evict_inode()) and so we are safe to flush
69		 * metadata blocks and the inode.
70		 */
71		ret = sync_mapping_buffers(inode->i_mapping);
72		if (ret)
73			break;
74		ret = sync_inode_metadata(inode, 1);
75		if (ret)
76			break;
77	}
78	dput(dentry);
79	return ret;
80}
81
82static int ext4_fsync_nojournal(struct file *file, loff_t start, loff_t end,
83				int datasync, bool *needs_barrier)
84{
85	struct inode *inode = file->f_inode;
86	int ret;
87
88	ret = generic_buffers_fsync_noflush(file, start, end, datasync);
89	if (!ret)
90		ret = ext4_sync_parent(inode);
91	if (test_opt(inode->i_sb, BARRIER))
92		*needs_barrier = true;
93
94	return ret;
95}
96
97static int ext4_fsync_journal(struct inode *inode, bool datasync,
98			     bool *needs_barrier)
99{
100	struct ext4_inode_info *ei = EXT4_I(inode);
101	journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
102	tid_t commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
103
104	/*
105	 * Fastcommit does not really support fsync on directories or other
106	 * special files. Force a full commit.
107	 */
108	if (!S_ISREG(inode->i_mode))
109		return ext4_force_commit(inode->i_sb);
110
111	if (journal->j_flags & JBD2_BARRIER &&
112	    !jbd2_trans_will_send_data_barrier(journal, commit_tid))
113		*needs_barrier = true;
114
115	return ext4_fc_commit(journal, commit_tid);
116}
117
118/*
119 * akpm: A new design for ext4_sync_file().
120 *
121 * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
122 * There cannot be a transaction open by this task.
123 * Another task could have dirtied this inode.  Its data can be in any
124 * state in the journalling system.
125 *
126 * What we do is just kick off a commit and wait on it.  This will snapshot the
127 * inode to disk.
128 */
129int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
130{
131	int ret = 0, err;
132	bool needs_barrier = false;
133	struct inode *inode = file->f_mapping->host;
134
135	if (unlikely(ext4_forced_shutdown(inode->i_sb)))
136		return -EIO;
137
138	ASSERT(ext4_journal_current_handle() == NULL);
139
140	trace_ext4_sync_file_enter(file, datasync);
141
142	if (sb_rdonly(inode->i_sb)) {
143		/* Make sure that we read updated s_ext4_flags value */
144		smp_rmb();
145		if (ext4_forced_shutdown(inode->i_sb))
146			ret = -EROFS;
147		goto out;
148	}
149
150	if (!EXT4_SB(inode->i_sb)->s_journal) {
151		ret = ext4_fsync_nojournal(file, start, end, datasync,
152					   &needs_barrier);
153		if (needs_barrier)
154			goto issue_flush;
155		goto out;
156	}
157
158	ret = file_write_and_wait_range(file, start, end);
159	if (ret)
160		goto out;
161
162	/*
163	 *  The caller's filemap_fdatawrite()/wait will sync the data.
164	 *  Metadata is in the journal, we wait for proper transaction to
165	 *  commit here.
166	 */
167	ret = ext4_fsync_journal(inode, datasync, &needs_barrier);
168
169issue_flush:
170	if (needs_barrier) {
171		err = blkdev_issue_flush(inode->i_sb->s_bdev);
172		if (!ret)
173			ret = err;
174	}
175out:
176	err = file_check_and_advance_wb_err(file);
177	if (ret == 0)
178		ret = err;
179	trace_ext4_sync_file_exit(inode, ret);
180	return ret;
181}
182