block: Stop using byte offsets

All callers of the stacking functions use 512-byte sector units rather
than byte offsets.  Simplify the code so the stacking functions take
sectors when specifying data offsets.

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

block/blk-settings.c

@@ -507,7 +507,7 @@ static unsigned int lcm(unsigned int a, unsigned int b)
  * blk_stack_limits - adjust queue_limits for stacked devices
  * @t:	the stacking driver limits (top device)
  * @b:  the underlying queue limits (bottom, component device)
- * @offset:  offset to beginning of data within component device
+ * @start:  first data sector within component device
  *
  * Description:
  *    This function is used by stacking drivers like MD and DM to ensure
@@ -525,10 +525,9 @@ static unsigned int lcm(unsigned int a, unsigned int b)
  *    the alignment_offset is undefined.
  */
 int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
-		     sector_t offset)
+		     sector_t start)
 {
-	sector_t alignment;
-	unsigned int top, bottom, ret = 0;
+	unsigned int top, bottom, alignment, ret = 0;
 
 	t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
 	t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
@@ -548,7 +547,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 
 	t->misaligned |= b->misaligned;
 
-	alignment = queue_limit_alignment_offset(b, offset);
+	alignment = queue_limit_alignment_offset(b, start);
 
 	/* Bottom device has different alignment.  Check that it is
 	 * compatible with the current top alignment.
@@ -611,11 +610,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 
 	/* Discard alignment and granularity */
 	if (b->discard_granularity) {
-		unsigned int granularity = b->discard_granularity;
-		offset &= granularity - 1;
-
-		alignment = (granularity + b->discard_alignment - offset)
-			& (granularity - 1);
+		alignment = queue_limit_discard_alignment(b, start);
 
 		if (t->discard_granularity != 0 &&
 		    t->discard_alignment != alignment) {
@@ -657,7 +652,7 @@ int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
 
 	start += get_start_sect(bdev);
 
-	return blk_stack_limits(t, &bq->limits, start << 9);
+	return blk_stack_limits(t, &bq->limits, start);
 }
 EXPORT_SYMBOL(bdev_stack_limits);
 
@@ -668,19 +663,16 @@ EXPORT_SYMBOL(bdev_stack_limits);
  * @offset:  offset to beginning of data within component device
  *
  * Description:
- *    Merges the limits for two queues.  Returns 0 if alignment
- *    didn't change.  Returns -1 if adding the bottom device caused
- *    misalignment.
+ *    Merges the limits for a top level gendisk and a bottom level
+ *    block_device.
  */
 void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
 		       sector_t offset)
 {
 	struct request_queue *t = disk->queue;
 	struct request_queue *b = bdev_get_queue(bdev);
 
-	offset += get_start_sect(bdev) << 9;
-
-	if (blk_stack_limits(&t->limits, &b->limits, offset) < 0) {
+	if (bdev_stack_limits(&t->limits, bdev, offset >> 9) < 0) {
 		char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
 
 		disk_name(disk, 0, top);

fs/partitions/check.c

@@ -412,9 +412,10 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno,
 	pdev = part_to_dev(p);
 
 	p->start_sect = start;
-	p->alignment_offset = queue_sector_alignment_offset(disk->queue, start);
-	p->discard_alignment = queue_sector_discard_alignment(disk->queue,
-							      start);
+	p->alignment_offset =
+		queue_limit_alignment_offset(&disk->queue->limits, start);
+	p->discard_alignment =
+		queue_limit_discard_alignment(&disk->queue->limits, start);
 	p->nr_sects = len;
 	p->partno = partno;
 	p->policy = get_disk_ro(disk);

include/linux/blkdev.h

@@ -1112,18 +1112,13 @@ static inline int queue_alignment_offset(struct request_queue *q)
 	return q->limits.alignment_offset;
 }
 
-static inline int queue_limit_alignment_offset(struct queue_limits *lim, sector_t offset)
+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);
 
-	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 queue_limit_alignment_offset(&q->limits, sector << 9);
+	return (granularity + lim->alignment_offset - alignment)
+		& (granularity - 1);
 }
 
 static inline int bdev_alignment_offset(struct block_device *bdev)
@@ -1147,10 +1142,8 @@ static inline int queue_discard_alignment(struct request_queue *q)
 	return q->limits.discard_alignment;
 }
 
-static inline int queue_sector_discard_alignment(struct request_queue *q,
-						 sector_t sector)
+static inline int queue_limit_discard_alignment(struct queue_limits *lim, sector_t sector)
 {
-	struct queue_limits *lim = &q->limits;
 	unsigned int alignment = (sector << 9) & (lim->discard_granularity - 1);
 
 	return (lim->discard_granularity + lim->discard_alignment - alignment)