ext4: prevent data corruption with journaling + DAX (e9072d85) · Commits · 戴 / test

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

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 @@ 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 (migrate) {
		if (flags & EXT4_EXTENTS_FL)
		err = ext4_ext_migrate(inode);

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