From a63bea06c1617175c68677da4810dfd120da2bd5 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Wed, 8 Oct 2014 18:26:13 -0400 Subject: [PATCH] block: fix alignment_offset math that assumes io_min is a power-of-2 commit b8839b8c55f3fdd60dc36abcda7e0266aff7985c 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 Acked-by: Martin K. Petersen Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/blk-settings.c | 4 ++-- include/linux/blkdev.h | 5 ++--- 2 files changed, 4 insertions(+), 5 deletions(-) diff --git a/block/blk-settings.c b/block/blk-settings.c index 53309333c2f0..ec00a0f75212 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -553,7 +553,7 @@ 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; } @@ -594,7 +594,7 @@ 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)) { diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 2fdb4a451b49..494d228a91dd 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -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) -- 2.20.1