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, bit: 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, bit: EXT4_STATE_NEWENTRY)) {
57 ext4_clear_inode_state(inode, bit: 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(mapping: inode->i_mapping);
72 if (ret)
73 break;
74 ret = sync_inode_metadata(inode, wait: 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(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(sb: inode->i_sb);
110
111 if (journal->j_flags & JBD2_BARRIER &&
112 !jbd2_trans_will_send_data_barrier(journal, tid: 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 ret = ext4_emergency_state(sb: inode->i_sb);
136 if (unlikely(ret))
137 return ret;
138
139 ASSERT(ext4_journal_current_handle() == NULL);
140
141 trace_ext4_sync_file_enter(file, datasync);
142
143 if (sb_rdonly(sb: inode->i_sb))
144 goto out;
145
146 if (!EXT4_SB(sb: inode->i_sb)->s_journal) {
147 ret = ext4_fsync_nojournal(file, start, end, datasync,
148 needs_barrier: &needs_barrier);
149 if (needs_barrier)
150 goto issue_flush;
151 goto out;
152 }
153
154 ret = file_write_and_wait_range(file, start, end);
155 if (ret)
156 goto out;
157
158 /*
159 * The caller's filemap_fdatawrite()/wait will sync the data.
160 * Metadata is in the journal, we wait for proper transaction to
161 * commit here.
162 */
163 ret = ext4_fsync_journal(inode, datasync, needs_barrier: &needs_barrier);
164
165issue_flush:
166 if (needs_barrier) {
167 err = blkdev_issue_flush(bdev: inode->i_sb->s_bdev);
168 if (!ret)
169 ret = err;
170 }
171out:
172 err = file_check_and_advance_wb_err(file);
173 if (ret == 0)
174 ret = err;
175 trace_ext4_sync_file_exit(inode, ret);
176 return ret;
177}
178