Commit 07d098e6 authored by Mike Snitzer's avatar Mike Snitzer Committed by Jens Axboe
Browse files

block: allow 'chunk_sectors' to be non-power-of-2 



It is possible, albeit more unlikely, for a block device to have a non
power-of-2 for chunk_sectors (e.g. 10+2 RAID6 with 128K chunk_sectors,
which results in a full-stripe size of 1280K. This causes the RAID6's
io_opt to be advertised as 1280K, and a stacked device _could_ then be
made to use a blocksize, aka chunk_sectors, that matches non power-of-2
io_opt of underlying RAID6 -- resulting in stacked device's
chunk_sectors being a non power-of-2).

Update blk_queue_chunk_sectors() and blk_max_size_offset() to
accommodate drivers that need a non power-of-2 chunk_sectors.

Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Reviewed-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 22ada802

block/blk-settings.c

+4 −6
Original line number Diff line number Diff line
@@ -172,15 +172,13 @@ EXPORT_SYMBOL(blk_queue_max_hw_sectors); 
 *

 * Description:

 *    If a driver doesn't want IOs to cross a given chunk size, it can set

 *    this limit and prevent merging across chunks. Note that the chunk size

 *    must currently be a power-of-2 in sectors. Also note that the block

 *    layer must accept a page worth of data at any offset. So if the

 *    crossing of chunks is a hard limitation in the driver, it must still be

 *    prepared to split single page bios.

 *    this limit and prevent merging across chunks. Note that the block layer

 *    must accept a page worth of data at any offset. So if the crossing of

 *    chunks is a hard limitation in the driver, it must still be prepared

 *    to split single page bios.

 **/

void blk_queue_chunk_sectors(struct request_queue *q, unsigned int chunk_sectors)

{

	BUG_ON(!is_power_of_2(chunk_sectors));

	q->limits.chunk_sectors = chunk_sectors;

}

EXPORT_SYMBOL(blk_queue_chunk_sectors);

include/linux/blkdev.h

+9 −3
Original line number Diff line number Diff line
@@ -1063,11 +1063,17 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q, 
static inline unsigned int blk_max_size_offset(struct request_queue *q,

					       sector_t offset)

{

	if (!q->limits.chunk_sectors)

	unsigned int chunk_sectors = q->limits.chunk_sectors;



	if (!chunk_sectors)

		return q->limits.max_sectors;



	return min(q->limits.max_sectors, (unsigned int)(q->limits.chunk_sectors -

			(offset & (q->limits.chunk_sectors - 1))));

	if (likely(is_power_of_2(chunk_sectors)))

		chunk_sectors -= offset & (chunk_sectors - 1);

	else

		chunk_sectors -= sector_div(offset, chunk_sectors);



	return min(q->limits.max_sectors, chunk_sectors);

}



static inline unsigned int blk_rq_get_max_sectors(struct request *rq,

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