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

Jeff Liu
2013-05-02T06:54:22Z

On 05/02/2013 09:13 AM, Dave Chinner wrote:
> On Wed, May 01, 2013 at 10:25:19PM +0800, Jeff Liu wrote:
>> 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");
>
> Same comment again about single line format strings. Otherwise it's
> ok.
Ah, sorry! I misunderstood the comments of Mark before. I was bluffed
into believing that I should cut the length of log string as short as
possible. :(

It will be fixed so.

Thanks,
-Jeff