Re: [PATCH v2] block: fix alignment_offset math that assumes io_min is a power-of-2

From: Martin K. Petersen
Date: Wed Oct 08 2014 - 20:23:27 EST

>>>>> "Mike" == Mike Snitzer <snitzer@xxxxxxxxxx> writes:

Mike> The math in both blk_stack_limits() and
Mike> queue_limit_alignment_offset() assume that a block device's io_min
Mike> (aka minimum_io_size) is always a power-of-2. Fix the math such
Mike> that it works for non-power-of-2 io_min.

Mike> This issue (of alignment_offset != 0) became apparent when testing
Mike> dm-thinp with a thinp blocksize that matches a RAID6 stripesize of
Mike> 1280K. Commit fdfb4c8c1 ("dm thin: set minimum_io_size to pool's
Mike> data block size") unlocked the potential for alignment_offset != 0
Mike> due to the dm-thin-pool's io_min possibly being a non-power-of-2.

Looks good to me, Mike.

Acked-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>

Martin K. Petersen Oracle Linux Engineering
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