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block: support different tag allocation policy

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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: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Shaohua Li
2015-01-15 17:32:25 -08:00
committed by Jens Axboe
parent bb5c3cdda3
commit ee1b6f7aff
6 changed files with 39 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files
block/blk-tag.c
+25 -8
View File
@@ -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 {
tag = find_first_zero_bit(bqt->tag_map, max_depth);
if (tag >= max_depth)
return 1;
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;