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

To: Jeff Liu <jeff.liu@xxxxxxxxxx>
Subject: Re: [PATCH 2/2 v2] xfs: Don't keep silent if sunit/swidth can not be changed via mount
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 2 May 2013 11:13:02 +1000
Cc: "xfs@xxxxxxxxxxx" <xfs@xxxxxxxxxxx>, Mark Tinguely <tinguely@xxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <518125CF.3050806@xxxxxxxxxx>
References: <518125CF.3050806@xxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
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.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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