block: Fix incorrect alignment offset reporting and update documentation
queue_sector_alignment_offset returned the wrong value which caused
partitions to report an incorrect alignment_offset. Since offset
alignment calculation is needed several places it has been split into a
separate helper function. The topology stacking function has been
updated accordingly.
Furthermore, comments have been added to clarify how the stacking
function works.
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Tested-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 784a919..59b832b 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1116,11 +1116,18 @@
return q->limits.alignment_offset;
}
+static inline int queue_limit_alignment_offset(struct queue_limits *lim, sector_t offset)
+{
+ unsigned int granularity = max(lim->physical_block_size, lim->io_min);
+
+ offset &= granularity - 1;
+ return (granularity + lim->alignment_offset - offset) & (granularity - 1);
+}
+
static inline int queue_sector_alignment_offset(struct request_queue *q,
sector_t sector)
{
- return ((sector << 9) - q->limits.alignment_offset)
- & (q->limits.io_min - 1);
+ return queue_limit_alignment_offset(&q->limits, sector << 9);
}
static inline int bdev_alignment_offset(struct block_device *bdev)