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Commit e9072d85 authored by Ross Zwisler's avatar Ross Zwisler Committed by Theodore Ts'o
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ext4: prevent data corruption with journaling + DAX 

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: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Cc: stable@vger.kernel.org
parent 559db4c6

fs/ext4/inode.c

+0 −5
Original line number Diff line number Diff line
@@ -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);

fs/ext4/ioctl.c

+13 −3
Original line number Diff line number Diff line
@@ -290,10 +290,20 @@ static int ext4_ioctl_setflags(struct inode *inode, 
	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 (migrate) {

		if (flags & EXT4_EXTENTS_FL)

			err = ext4_ext_migrate(inode);