Messages in this thread | | | Date | Wed, 8 Oct 2014 18:28:41 -0400 | From | Mike Snitzer <> | Subject | Re: block: fix alignment_offset math that assumes io_min is a power-of-2 |
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On Wed, Oct 08 2014 at 6:12pm -0400, Jens Axboe <axboe@kernel.dk> wrote:
> On 10/08/2014 04:05 PM, Mike Snitzer wrote: > > The math in both blk_stack_limits() and queue_limit_alignment_offset() > > assume that a block device's io_min (aka minimum_io_size) is always a > > power-of-2. Fix the math such that it works for non-power-of-2 io_min. > > > > This issue (of alignment_offset != 0) became apparent when testing > > dm-thinp with a thinp blocksize that matches a RAID6 stripesize of > > 1280K. Commit fdfb4c8c1 ("dm thin: set minimum_io_size to pool's data > > block size") unlocked the potential for alignment_offset != 0 due to > > the dm-thin-pool's io_min possibly being a non-power-of-2. > > Well that sucks, AND with a mask is considerably cheaper than a MOD...
Yeah, certainly does suck (please note v2 that I just sent). The MODs shouldn't kill us, these functions aren't called in any real hot path. A storm at boot maybe.. or SCSI rescan but...
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