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block: add notion of a chunk size for request merging

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Some drivers have different limits on what size a request should
optimally be, depending on the offset of the request. Similar to
dividing a device into chunks. Add a setting that allows the driver
to inform the block layer of such a chunk size. The block layer will
then prevent merging across the chunks.

This is needed to optimally support NVMe with a non-zero stripe size.

Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jens Axboe 2014-06-05 13:38:39 -06:00
parent 046f153343
commit 762380ad93
3 changed files with 41 additions and 2 deletions
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22
include/linux/blkdev.h
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@ -280,6 +280,7 @@ struct queue_limits {
unsigned long seg_boundary_mask;
unsigned int max_hw_sectors;
unsigned int chunk_sectors;
unsigned int max_sectors;
unsigned int max_segment_size;
unsigned int physical_block_size;
@ -910,6 +911,20 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
return q->limits.max_sectors;
}
/*
* Return maximum size of a request at given offset. Only valid for
* file system requests.
*/
static inline unsigned int blk_max_size_offset(struct request_queue *q,
sector_t offset)
{
if (!q->limits.chunk_sectors)
return q->limits.max_hw_sectors;
return q->limits.chunk_sectors -
(offset & (q->limits.chunk_sectors - 1));
}
static inline unsigned int blk_rq_get_max_sectors(struct request *rq)
{
struct request_queue *q = rq->q;
@ -917,7 +932,11 @@ static inline unsigned int blk_rq_get_max_sectors(struct request *rq)
if (unlikely(rq->cmd_type == REQ_TYPE_BLOCK_PC))
return q->limits.max_hw_sectors;
return blk_queue_get_max_sectors(q, rq->cmd_flags);
if (!q->limits.chunk_sectors)
return blk_queue_get_max_sectors(q, rq->cmd_flags);
return min(blk_max_size_offset(q, blk_rq_pos(rq)),
blk_queue_get_max_sectors(q, rq->cmd_flags));
}
static inline unsigned int blk_rq_count_bios(struct request *rq)
@ -983,6 +1002,7 @@ extern void blk_queue_make_request(struct request_queue *, make_request_fn *);
extern void blk_queue_bounce_limit(struct request_queue *, u64);
extern void blk_limits_max_hw_sectors(struct queue_limits *, unsigned int);
extern void blk_queue_max_hw_sectors(struct request_queue *, unsigned int);
extern void blk_queue_chunk_sectors(struct request_queue *, unsigned int);
extern void blk_queue_max_segments(struct request_queue *, unsigned short);
extern void blk_queue_max_segment_size(struct request_queue *, unsigned int);
extern void blk_queue_max_discard_sectors(struct request_queue *q,