From 762380ad9322951cea4ce9d24864265f9c66a916 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 5 Jun 2014 13:38:39 -0600 Subject: 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/blk-settings.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'block/blk-settings.c') diff --git a/block/blk-settings.c b/block/blk-settings.c index 5d21239bc859..a2b9cb195e70 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 -- cgit v1.2.3