block: discard granularity might not be power of 2

In MD raid case, discard granularity might not be power of 2, for example, a
4-disk raid5 has 3*chunk_size discard granularity. Correct the calculation for
such cases.

Reported-by: Neil Brown <neilb@suse.de>
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 4 insertions, 3 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c9d233e727f2..acb4f7bbbd32 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1188,13 +1188,14 @@ static inline int queue_discard_alignment(struct request_queue *q)
 
 static inline int queue_limit_discard_alignment(struct queue_limits *lim, sector_t sector)
 {
-        unsigned int alignment = (sector << 9) & (lim->discard_granularity - 1);
+        sector_t alignment = sector << 9;
+        alignment = sector_div(alignment, lim->discard_granularity);
 
         if (!lim->max_discard_sectors)
                 return 0;
 
-        return (lim->discard_granularity + lim->discard_alignment - alignment)
-                & (lim->discard_granularity - 1);
+        alignment = lim->discard_granularity + lim->discard_alignment - alignment;
+        return sector_div(alignment, lim->discard_granularity);
 }
 
 static inline int bdev_discard_alignment(struct block_device *bdev)