From 762380ad9322951cea4ce9d24864265f9c66a916 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 5 Jun 2014 13:38:39 -0600 Subject: [PATCH] block: add notion of a chunk size for request merging 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 --- block/bio.c | 3 ++- block/blk-settings.c | 18 ++++++++++++++++++ include/linux/blkdev.h | 22 +++++++++++++++++++++- 3 files changed, 41 insertions(+), 2 deletions(-) diff --git a/block/bio.c b/block/bio.c index 96d28eee8a1ee..97e832cc9b9cb 100644 --- a/block/bio.c +++ b/block/bio.c @@ -849,7 +849,8 @@ int bio_add_page(struct bio *bio, struct page *page, unsigned int len, unsigned int offset) { struct request_queue *q = bdev_get_queue(bio->bi_bdev); - return __bio_add_page(q, bio, page, len, offset, queue_max_sectors(q)); + + return __bio_add_page(q, bio, page, len, offset, blk_max_size_offset(q, bio->bi_iter.bi_sector)); } EXPORT_SYMBOL(bio_add_page); diff --git a/block/blk-settings.c b/block/blk-settings.c index 5d21239bc8599..a2b9cb195e70e 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -113,6 +113,7 @@ void blk_set_default_limits(struct queue_limits *lim) lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK; lim->max_segment_size = BLK_MAX_SEGMENT_SIZE; lim->max_sectors = lim->max_hw_sectors = BLK_SAFE_MAX_SECTORS; + lim->chunk_sectors = 0; lim->max_write_same_sectors = 0; lim->max_discard_sectors = 0; lim->discard_granularity = 0; @@ -276,6 +277,23 @@ void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_secto } EXPORT_SYMBOL(blk_queue_max_hw_sectors); +/** + * blk_queue_chunk_sectors - set size of the chunk for this queue + * @q: the request queue for the device + * @chunk_sectors: chunk sectors in the usual 512b unit + * + * 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. + **/ +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); + /** * blk_queue_max_discard_sectors - set max sectors for a single discard * @q: the request queue for the device diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 3cd426e971db6..dc2c703f05fd1 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -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, -- 2.39.2