block: Align max_hw_sectors to logical blocksize

Block device drivers do not have to call blk_queue_max_hw_sectors() to
set a limit on request size if the default limit BLK_SAFE_MAX_SECTORS
is acceptable. However, this limit (255 sectors) may not be aligned
to the device logical block size which cannot be used as is for a
request maximum size. This is the case for the null_blk device driver.

Modify blk_queue_max_hw_sectors() to make sure that the request size
limits specified by the max_hw_sectors and max_sectors queue limits
are always aligned to the device logical block size. Additionally, to
avoid introducing a dependence on the execution order of this function
with blk_queue_logical_block_size(), also modify
blk_queue_logical_block_size() to perform the same alignment when the
logical block size is set after max_hw_sectors.
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-settings.c

@@ -157,10 +157,16 @@ void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_secto
 		       __func__, max_hw_sectors);
 	}
 
+	max_hw_sectors = round_down(max_hw_sectors,
+				    limits->logical_block_size >> SECTOR_SHIFT);
 	limits->max_hw_sectors = max_hw_sectors;
+
 	max_sectors = min_not_zero(max_hw_sectors, limits->max_dev_sectors);
 	max_sectors = min_t(unsigned int, max_sectors, BLK_DEF_MAX_SECTORS);
+	max_sectors = round_down(max_sectors,
+				 limits->logical_block_size >> SECTOR_SHIFT);
 	limits->max_sectors = max_sectors;
+
 	q->backing_dev_info->io_pages = max_sectors >> (PAGE_SHIFT - 9);
 }
 EXPORT_SYMBOL(blk_queue_max_hw_sectors);
@@ -321,13 +327,20 @@ EXPORT_SYMBOL(blk_queue_max_segment_size);
  **/
 void blk_queue_logical_block_size(struct request_queue *q, unsigned int size)
 {
-	q->limits.logical_block_size = size;
+	struct queue_limits *limits = &q->limits;
 
-	if (q->limits.physical_block_size < size)
-		q->limits.physical_block_size = size;
+	limits->logical_block_size = size;
 
-	if (q->limits.io_min < q->limits.physical_block_size)
-		q->limits.io_min = q->limits.physical_block_size;
+	if (limits->physical_block_size < size)
+		limits->physical_block_size = size;
+
+	if (limits->io_min < limits->physical_block_size)
+		limits->io_min = limits->physical_block_size;
+
+	limits->max_hw_sectors =
+		round_down(limits->max_hw_sectors, size >> SECTOR_SHIFT);
+	limits->max_sectors =
+		round_down(limits->max_sectors, size >> SECTOR_SHIFT);
 }
 EXPORT_SYMBOL(blk_queue_logical_block_size);