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

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 2/2 v2] xfs: Don't keep silent if sunit/swidth can not be changed via mount
From: Jeff Liu <jeff.liu@xxxxxxxxxx>
Date: Thu, 02 May 2013 14:54:06 +0800
Cc: Mark Tinguely <tinguely@xxxxxxx>, "xfs@xxxxxxxxxxx" <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20130502011302.GS10481@dastard>
References: <518125CF.3050806@xxxxxxxxxx> <20130502011302.GS10481@dastard>
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121028 Thunderbird/16.0.2
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@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 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@xxxxxxxxxx>
>> Cc: Mark Tinguely <tinguely@xxxxxxx>
>> Cc: Dave Chinner <dchinner@xxxxxxxxxx>
>> ---
>>  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

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