block: Fix discard alignment calculation and printing

Discard alignment reporting for partitions was incorrect.  Update to
match the algorithm used elsewhere.

The alignment can be negative (misaligned).  Fix format string
accordingly.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 9b98173a8184..a41bcc8e140f 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1148,8 +1148,11 @@ static inline int queue_discard_alignment(struct request_queue *q)
 static inline int queue_sector_discard_alignment(struct request_queue *q,
                                                  sector_t sector)
 {
-        return ((sector << 9) - q->limits.discard_alignment)
-                & (q->limits.discard_granularity - 1);
+        struct queue_limits *lim = &q->limits;
+        unsigned int alignment = (sector << 9) & (lim->discard_granularity - 1);
+
+        return (lim->discard_granularity + lim->discard_alignment - alignment)
+                & (lim->discard_granularity - 1);
 }
 
 static inline unsigned int queue_discard_zeroes_data(struct request_queue *q)