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Commit e475bba2 authored by Martin K. Petersen's avatar Martin K. Petersen Committed by Jens Axboe
Browse files

block: Introduce helper to reset queue limits to default values 



DM reuses the request queue when swapping in a new device table
Introduce blk_set_default_limits() which can be used to reset the the
queue_limits prior to stacking devices.

Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Acked-by: default avatarAlasdair G Kergon <agk@redhat.com>
Acked-by: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 6923715a

block/blk-settings.c

+27 −6
Original line number Diff line number Diff line
@@ -95,6 +95,31 @@ void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn) 
}

EXPORT_SYMBOL_GPL(blk_queue_lld_busy);



/**

 * blk_set_default_limits - reset limits to default values

 * @limits:  the queue_limits structure to reset

 *

 * Description:

 *   Returns a queue_limit struct to its default state.  Can be used by

 *   stacking drivers like DM that stage table swaps and reuse an

 *   existing device queue.

 */

void blk_set_default_limits(struct queue_limits *lim)

{

	lim->max_phys_segments = MAX_PHYS_SEGMENTS;

	lim->max_hw_segments = MAX_HW_SEGMENTS;

	lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;

	lim->max_segment_size = MAX_SEGMENT_SIZE;

	lim->max_sectors = lim->max_hw_sectors = SAFE_MAX_SECTORS;

	lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;

	lim->bounce_pfn = BLK_BOUNCE_ANY;

	lim->alignment_offset = 0;

	lim->io_opt = 0;

	lim->misaligned = 0;

	lim->no_cluster = 0;

}

EXPORT_SYMBOL(blk_set_default_limits);



/**

 * blk_queue_make_request - define an alternate make_request function for a device

 * @q:  the request queue for the device to be affected
@@ -123,14 +148,8 @@ void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn) 
	 * set defaults

	 */

	q->nr_requests = BLKDEV_MAX_RQ;

	blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);

	blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);

	blk_queue_segment_boundary(q, BLK_SEG_BOUNDARY_MASK);

	blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE);



	q->make_request_fn = mfn;

	blk_queue_max_sectors(q, SAFE_MAX_SECTORS);

	blk_queue_logical_block_size(q, 512);

	blk_queue_dma_alignment(q, 511);

	blk_queue_congestion_threshold(q);

	q->nr_batching = BLK_BATCH_REQ;
@@ -143,6 +162,8 @@ void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn) 
	q->unplug_timer.function = blk_unplug_timeout;

	q->unplug_timer.data = (unsigned long)q;



	blk_set_default_limits(&q->limits);



	/*

	 * by default assume old behaviour and bounce for any highmem page

	 */

include/linux/blkdev.h

+1 −0
Original line number Diff line number Diff line
@@ -926,6 +926,7 @@ extern void blk_queue_alignment_offset(struct request_queue *q, 
				       unsigned int alignment);

extern void blk_queue_io_min(struct request_queue *q, unsigned int min);

extern void blk_queue_io_opt(struct request_queue *q, unsigned int opt);

extern void blk_set_default_limits(struct queue_limits *lim);

extern int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,

			    sector_t offset);

extern void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,