On Mon, Apr 29, 2013 at 07:44:18PM +0800, Jeff Liu wrote:
> From: Jie Liu <jeff.liu@xxxxxxxxxx>
>
> 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 will be silently ignored, so it's better to tell user
> that the alignment-changing can not take affect in one way or another.
>
> With this fix, the attempt to mount a storage without strip alignment
> setup on super block will failed if XFS_MOUNT_RETERR is enabled, or
> just ignore the given alignment and drop a warning to indicate the
> cause in syslog.
>
> # 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: no data alignment on superblock
>
> Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
>
> ---
> fs/xfs/xfs_mount.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> index 3806088..bc7fdd4 100644
> --- a/fs/xfs/xfs_mount.c
> +++ b/fs/xfs/xfs_mount.c
> @@ -924,6 +924,13 @@ xfs_update_alignment(xfs_mount_t *mp)
> sbp->sb_width = mp->m_swidth;
> mp->m_update_flags |= XFS_SB_WIDTH;
> }
> + } else {
> + xfs_warn(mp, "can not change alignment: "
> + "no data alignment on superblock");
> + if (mp->m_flags & XFS_MOUNT_RETERR)
> + return XFS_ERROR(EINVAL);
> + mp->m_dalign = 0;
> + mp->m_swidth = 0;
Can someone tell me why the XFS_MOUNT_RETERR flag exists?
It looks like dead code to me as the only time mp->m_dalign is set
prior to calling xfs_update_alignment() is the same code that sets
XFS_MOUNT_RETERR in xfs_parseargs().
IOWs, any time we enter this "if (mp->m_dalign)" branch in
xfs_update_alignment(), XFS_MOUNT_RETERR is going to be set and so
we should always be emitting a warning and returning an error.
If this is correct, Jeff, can you remove the XFS_MOUNT_RETERR flag
and get rid of all the dead code in xfs_update_alignment() at the
same time, please?
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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