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block: fix alignment_offset math that assumes io_min is a power-of-2

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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.

Signed-off-by: Mike Snitzer <[email protected]>
Cc: [email protected]
Acked-by: Martin K. Petersen <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Mike Snitzer 2014-10-08 18:26:13 -04:00 • committed by Jens Axboe
commit b8839b8c55
2 changed files with 4 additions and 5 deletions
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4
block/blk-settings.c
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@ -574,7 +574,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
bottom = max(b->physical_block_size, b->io_min) + alignment;
/* Verify that top and bottom intervals line up */
if (max(top, bottom) & (min(top, bottom) - 1)) {
if (max(top, bottom) % min(top, bottom)) {
t->misaligned = 1;
ret = -1;
}
@ -619,7 +619,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
/* Find lowest common alignment_offset */
t->alignment_offset = lcm(t->alignment_offset, alignment)
& (max(t->physical_block_size, t->io_min) - 1);
% max(t->physical_block_size, t->io_min);
/* Verify that new alignment_offset is on a logical block boundary */
if (t->alignment_offset & (t->logical_block_size - 1)) {