On Thu, May 02, 2013 at 07:27:53PM +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, 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@xxxxxxxxxx>
> Cc: Mark Tinguely <tinguely@xxxxxxx>
> Cc: Dave Chinner <dchinner@xxxxxxxxxx>
Applied.
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