[PATCH 3/4] xfs: disable noattr2/attr2 mount options for CRC enabled filesystems

[Dave Chinner]

From: Dave Chinner <dchinner at redhat.com>

attr2 format is always enabled for v5 superblock filesystems, so the
mount options to enable or disable it need to be cause mount errors.

Signed-off-by: Dave Chinner <dchinner at redhat.com>
Reviewed-by: Brian Foster <bfoster at redhat.com>
---
 Documentation/filesystems/xfs.txt |    3 +++
 fs/xfs/xfs_super.c                |   11 +++++++++++
 2 files changed, 14 insertions(+)

diff --git a/Documentation/filesystems/xfs.txt b/Documentation/filesystems/xfs.txt
index 3e4b3dd..83577f0 100644
--- a/Documentation/filesystems/xfs.txt
+++ b/Documentation/filesystems/xfs.txt
@@ -33,6 +33,9 @@ When mounting an XFS filesystem, the following options are accepted.
 	removing extended attributes) the on-disk superblock feature
 	bit field will be updated to reflect this format being in use.
 
+	CRC enabled filesystems always use the attr2 format, and so
+	will reject the noattr2 mount option if it is set.
+
   barrier
 	Enables the use of block layer write barriers for writes into
 	the journal and unwritten extent conversion.  This allows for
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index ea341ce..3033ba5 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1373,6 +1373,17 @@ xfs_finish_flags(
 	}
 
 	/*
+	 * V5 filesystems always use attr2 format for attributes.
+	 */
+	if (xfs_sb_version_hascrc(&mp->m_sb) &&
+	    (mp->m_flags & XFS_MOUNT_NOATTR2)) {
+		xfs_warn(mp,
+"Cannot mount a V5 filesystem as %s. %s is always enabled for V5 filesystems.",
+			MNTOPT_NOATTR2, MNTOPT_ATTR2);
+		return XFS_ERROR(EINVAL);
+	}
+
+	/*
 	 * mkfs'ed attr2 will turn on attr2 mount unless explicitly
 	 * told by noattr2 to turn it off
 	 */
-- 
1.7.10.4