xref: /openbmc/linux/fs/ext4/fsync.c (revision 95257987)
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  */
ext4_sync_parent(struct inode * inode)46 static 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 
ext4_fsync_nojournal(struct file * file,loff_t start,loff_t end,int datasync,bool * needs_barrier)82 static 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 
ext4_fsync_journal(struct inode * inode,bool datasync,bool * needs_barrier)97 static 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  */
ext4_sync_file(struct file * file,loff_t start,loff_t end,int datasync)129 int 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 
169 issue_flush:
170 	if (needs_barrier) {
171 		err = blkdev_issue_flush(inode->i_sb->s_bdev);
172 		if (!ret)
173 			ret = err;
174 	}
175 out:
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