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

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commit b8839b8c55 upstream.

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>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mike Snitzer
2014-10-08 18:26:13 -04:00
committed by Greg Kroah-Hartman
parent 29772e3e19
commit a63bea06c1
2 changed files with 4 additions and 5 deletions
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5
include/linux/blkdev.h
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@@ -1187,10 +1187,9 @@ static inline int queue_alignment_offset(struct request_queue *q)
static inline int queue_limit_alignment_offset(struct queue_limits *lim, sector_t sector)
{
unsigned int granularity = max(lim->physical_block_size, lim->io_min);
unsigned int alignment = (sector << 9) & (granularity - 1);
unsigned int alignment = sector_div(sector, granularity >> 9) << 9;
return (granularity + lim->alignment_offset - alignment)
& (granularity - 1);
return (granularity + lim->alignment_offset - alignment) % granularity;
}
static inline int bdev_alignment_offset(struct block_device *bdev)