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Re: [PATCH] xfs: Don't keep silent if sunit/swidth can not be changed vi

To: Mark Tinguely <tinguely@xxxxxxx>
Subject: Re: [PATCH] xfs: Don't keep silent if sunit/swidth can not be changed via mount
From: Jeff Liu <jeff.liu@xxxxxxxxxx>
Date: Tue, 30 Apr 2013 10:11:36 +0800
Cc: "xfs@xxxxxxxxxxx" <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <517E88E6.9070709@xxxxxxx>
References: <517E5D12.5010809@xxxxxxxxxx> <517E88E6.9070709@xxxxxxx>
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121028 Thunderbird/16.0.2
On 04/29/2013 10:51 PM, Mark Tinguely wrote:
> On 04/29/13 06:44, 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");
> suggest that you keep the string together so it can be searched.
>    "superblock does not support data alignment"
Do you means that the string would shown as: "superblock does not
support data alignment"?

Or "cannot change alignment: superblock does not support data alignment"?

I prefer to the later format because it can distinguish this special
case from the previous alignment validation procedure, i.e,
"alignment check failed: xxx".

Thanks,
-Jeff
> 
>> +                    if (mp->m_flags&  XFS_MOUNT_RETERR)
>> +                            return XFS_ERROR(EINVAL);
>> +                    mp->m_dalign = 0;
>> +                    mp->m_swidth = 0;
>>              }
>>      } else if ((mp->m_flags&  XFS_MOUNT_NOALIGN) != XFS_MOUNT_NOALIGN&&
>>              xfs_sb_version_hasdalign(&mp->m_sb)) {
> 
> 
> Thanks,
> 
> --Mark.
> 
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