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

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 <snitzer@redhat.com>
Cc: stable@vger.kernel.org
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/block/blk-settings.c b/block/blk-settings.c
index f1a1795a5683..aa02247d227e 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -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)) {