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Commit ee1b6f7a authored by Shaohua Li's avatar Shaohua Li Committed by Jens Axboe
Browse files

block: support different tag allocation policy 



The libata tag allocation is using a round-robin policy. Next patch will
make libata use block generic tag allocation, so let's add a policy to
tag allocation.

Currently two policies: FIFO (default) and round-robin.

Cc: Jens Axboe <axboe@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: default avatarShaohua Li <shli@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent bb5c3cdd

block/blk-tag.c

+25 −8
Original line number Diff line number Diff line
@@ -119,7 +119,7 @@ fail: 
}



static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,

						   int depth)

						int depth, int alloc_policy)

{

	struct blk_queue_tag *tags;
@@ -131,6 +131,8 @@ static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q, 
		goto fail;



	atomic_set(&tags->refcnt, 1);

	tags->alloc_policy = alloc_policy;

	tags->next_tag = 0;

	return tags;

fail:

	kfree(tags);
@@ -140,10 +142,11 @@ fail: 
/**

 * blk_init_tags - initialize the tag info for an external tag map

 * @depth:	the maximum queue depth supported

 * @alloc_policy: tag allocation policy

 **/

struct blk_queue_tag *blk_init_tags(int depth)

struct blk_queue_tag *blk_init_tags(int depth, int alloc_policy)

{

	return __blk_queue_init_tags(NULL, depth);

	return __blk_queue_init_tags(NULL, depth, alloc_policy);

}

EXPORT_SYMBOL(blk_init_tags);
@@ -152,19 +155,20 @@ EXPORT_SYMBOL(blk_init_tags); 
 * @q:  the request queue for the device

 * @depth:  the maximum queue depth supported

 * @tags: the tag to use

 * @alloc_policy: tag allocation policy

 *

 * Queue lock must be held here if the function is called to resize an

 * existing map.

 **/

int blk_queue_init_tags(struct request_queue *q, int depth,

			struct blk_queue_tag *tags)

			struct blk_queue_tag *tags, int alloc_policy)

{

	int rc;



	BUG_ON(tags && q->queue_tags && tags != q->queue_tags);



	if (!tags && !q->queue_tags) {

		tags = __blk_queue_init_tags(q, depth);

		tags = __blk_queue_init_tags(q, depth, alloc_policy);



		if (!tags)

			return -ENOMEM;
@@ -344,9 +348,21 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq) 
	}



	do {

		if (bqt->alloc_policy == BLK_TAG_ALLOC_FIFO) {

			tag = find_first_zero_bit(bqt->tag_map, max_depth);

			if (tag >= max_depth)

				return 1;

		} else {

			int start = bqt->next_tag;

			int size = min_t(int, bqt->max_depth, max_depth + start);

			tag = find_next_zero_bit(bqt->tag_map, size, start);

			if (tag >= size && start + size > bqt->max_depth) {

				size = start + size - bqt->max_depth;

				tag = find_first_zero_bit(bqt->tag_map, size);

			}

			if (tag >= size)

				return 1;

		}



	} while (test_and_set_bit_lock(tag, bqt->tag_map));

	/*
@@ -354,6 +370,7 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq) 
	 * See blk_queue_end_tag for details.

	 */



	bqt->next_tag = (tag + 1) % bqt->max_depth;

	rq->cmd_flags |= REQ_QUEUED;

	rq->tag = tag;

	bqt->tag_index[tag] = rq;

drivers/block/osdblk.c

+1 −1
Original line number Diff line number Diff line
@@ -423,7 +423,7 @@ static int osdblk_init_disk(struct osdblk_device *osdev) 
	}



	/* switch queue to TCQ mode; allocate tag map */

	rc = blk_queue_init_tags(q, OSDBLK_MAX_REQ, NULL);

	rc = blk_queue_init_tags(q, OSDBLK_MAX_REQ, NULL, BLK_TAG_ALLOC_FIFO);

	if (rc) {

		blk_cleanup_queue(q);

		put_disk(disk);

drivers/scsi/scsi_scan.c

+2 −1
Original line number Diff line number Diff line
@@ -290,7 +290,8 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget, 
	if (!shost_use_blk_mq(sdev->host) &&

	    (shost->bqt || shost->hostt->use_blk_tags)) {

		blk_queue_init_tags(sdev->request_queue,

				    sdev->host->cmd_per_lun, shost->bqt);

				    sdev->host->cmd_per_lun, shost->bqt,

				    shost->hostt->tag_alloc_policy);

	}

	scsi_change_queue_depth(sdev, sdev->host->cmd_per_lun);

include/linux/blkdev.h

+6 −2
Original line number Diff line number Diff line
@@ -272,7 +272,11 @@ struct blk_queue_tag { 
	int max_depth;			/* what we will send to device */

	int real_max_depth;		/* what the array can hold */

	atomic_t refcnt;		/* map can be shared */

	int alloc_policy;		/* tag allocation policy */

	int next_tag;			/* next tag */

};

#define BLK_TAG_ALLOC_FIFO 0 /* allocate starting from 0 */

#define BLK_TAG_ALLOC_RR 1 /* allocate starting from last allocated tag */



#define BLK_SCSI_MAX_CMDS	(256)

#define BLK_SCSI_CMD_PER_LONG	(BLK_SCSI_MAX_CMDS / (sizeof(long) * 8))
@@ -1139,11 +1143,11 @@ static inline bool blk_needs_flush_plug(struct task_struct *tsk) 
extern int blk_queue_start_tag(struct request_queue *, struct request *);

extern struct request *blk_queue_find_tag(struct request_queue *, int);

extern void blk_queue_end_tag(struct request_queue *, struct request *);

extern int blk_queue_init_tags(struct request_queue *, int, struct blk_queue_tag *);

extern int blk_queue_init_tags(struct request_queue *, int, struct blk_queue_tag *, int);

extern void blk_queue_free_tags(struct request_queue *);

extern int blk_queue_resize_tags(struct request_queue *, int);

extern void blk_queue_invalidate_tags(struct request_queue *);

extern struct blk_queue_tag *blk_init_tags(int);

extern struct blk_queue_tag *blk_init_tags(int, int);

extern void blk_free_tags(struct blk_queue_tag *);



static inline struct request *blk_map_queue_find_tag(struct blk_queue_tag *bqt,

include/scsi/scsi_host.h

+3 −0
Original line number Diff line number Diff line
@@ -402,6 +402,9 @@ struct scsi_host_template { 
	 */

	unsigned char present;



	/* If use block layer to manage tags, this is tag allocation policy */

	int tag_alloc_policy;



	/*

	 * Let the block layer assigns tags to all commands.

	 */