On 10/08/2014 04:28 PM, Mike Snitzer wrote: > On Wed, Oct 08 2014 at 6:12pm -0400, > Jens Axboe <ax...@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...
I had it mixed up with the recent blk_max_size_offset() - you are right, this is not in a hot path. For that case, I don't really care, it's fine. Is v2 runtime tested? -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/