[PATCH v3 2/2] xfs: Don't keep silent if sunit/swidth can not be changed via mount

[Mark Tinguely]

On 05/02/13 06:27, Jeff Liu wrote:
> From: Jie Liu<jeff.liu at 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, e.g.
> # 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
> .......
> XFS (sdb1): cannot change alignment: superblock does not support data
> alignment
>
> Signed-off-by: Jie Liu<jeff.liu at oracle.com>

Looks good.

Reviewed-by: Mark Tinguely <tinguely at sgi.com>