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ext4: prevent data corruption with journaling + DAX

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The current code has the potential for data corruption when changing an
inode's journaling mode, as that can result in a subsequent unsafe change
in S_DAX.

I've captured an instance of this data corruption in the following fstest:

https://patchwork.kernel.org/patch/9948377/

Prevent this data corruption from happening by disallowing changes to the
journaling mode if the '-o dax' mount option was used.  This means that for
a given filesystem we could have a mix of inodes using either DAX or
data journaling, but whatever state the inodes are in will be held for the
duration of the mount.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: stable@vger.kernel.org
This commit is contained in:
Ross Zwisler 2017-10-12 11:54:08 -04:00 committed by Theodore Ts'o
parent 559db4c6d7
commit e9072d859d
2 changed files with 13 additions and 8 deletions
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5
fs/ext4/inode.c
View File

@ -6004,11 +6004,6 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
ext4_clear_inode_flag(inode, EXT4_INODE_JOURNAL_DATA);
}
ext4_set_aops(inode);
/*
* Update inode->i_flags after EXT4_INODE_JOURNAL_DATA was updated.
* E.g. S_DAX may get cleared / set.
*/
ext4_set_inode_flags(inode);
jbd2_journal_unlock_updates(journal);
percpu_up_write(&sbi->s_journal_flag_rwsem);

16
fs/ext4/ioctl.c
View File

@ -290,10 +290,20 @@ flags_err:
if (err)
goto flags_out;
if ((jflag ^ oldflags) & (EXT4_JOURNAL_DATA_FL))
if ((jflag ^ oldflags) & (EXT4_JOURNAL_DATA_FL)) {
/*
* Changes to the journaling mode can cause unsafe changes to
* S_DAX if we are using the DAX mount option.
*/
if (test_opt(inode->i_sb, DAX)) {
err = -EBUSY;
goto flags_out;
}
err = ext4_change_inode_journal_flag(inode, jflag);
if (err)
goto flags_out;
if (err)
goto flags_out;
}
if (migrate) {
if (flags & EXT4_EXTENTS_FL)
err = ext4_ext_migrate(inode);