[PATCH 2/2 v2] xfs: Don't keep silent if sunit/swidth can not be changed via mount

Jeff Liu
2013-05-01T14:25:30Z

From: Jie Liu <jeff.liu@oracle.com>

As per the mount man page, sunit and swidth can be changed via
mount options. For XFS, on the face of it, those options seems
works if the specified alignments is properly, e.g.
# mount -o sunit=4096,swidth=8192 /dev/sdb1 /mnt
# mount | grep sdb1
/dev/sdb1 on /mnt type xfs (rw,sunit=4096,swidth=8192)

However, neither sunit nor swidth is shown from the xfs_info output.
# xfs_info /mnt
meta-data=/dev/sdb1 isize=256 agcount=4, agsize=262144 blks
= sectsz=512 attr=2
data = bsize=4096 blocks=1048576, imaxpct=25
= sunit=0 swidth=0 blks
^^^^^^^^^^^^^^^^^^^^^^^^^^
naming =version 2 bsize=4096 ascii-ci=0
log =internal bsize=4096 blocks=2560, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0

The reason is that the alignment can only be changed if the relevant
super block is already configured with alignments, otherwise, the
given value is silently ignored.

With this fix, the attempt to mount a storage without strip alignment
setup on a super block will get an error with a warning in syslog to
indicate the true cause.

# mount -o sunit=4096,swidth=8192 /dev/sdb1 /mnt
mount: wrong fs type, bad option, bad superblock on /dev/sdb1,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
# dmesg|tail
.......
XFS (sdb1): can not change alignment: superblock does not support data
alignment

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Cc: Mark Tinguely <tinguely@sgi.com>
Cc: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/xfs_mount.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 29e8de8..2836ef6 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -909,6 +909,10 @@ xfs_update_alignment(xfs_mount_t *mp)
sbp->sb_width = mp->m_swidth;
mp->m_update_flags |= XFS_SB_WIDTH;
}
+ } else {
+ xfs_warn(mp, "cannot change alignment: "
+ "superblock does not support data alignment");
+ return XFS_ERROR(EINVAL);
}
} else if ((mp->m_flags & XFS_MOUNT_NOALIGN) != XFS_MOUNT_NOALIGN &&
xfs_sb_version_hasdalign(&mp->m_sb)) {
--
1.7.9.5