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.
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/blk-settings.c | 10 ++++------
include/linux/blkdev.h | 12 +++++++++---
2 files changed, 13 insertions(+), 9 deletions(-)
diff --git a/block/blk-settings.c b/block/blk-settings.c
index b2e1a929a6db..5ea3de48afba 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -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);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index bb5636cc17b9..51d98a595943 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1059,11 +1059,17 @@ 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,
--
2.15.0
