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: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-tag.c b/block/blk-tag.c
index a185b86..f0344e6 100644
--- a/block/blk-tag.c
+++ b/block/blk-tag.c
@@ -119,7 +119,7 @@
}
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 @@
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 @@
/**
* 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 @@
* @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 @@
}
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 @@
* 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;
diff --git a/drivers/block/osdblk.c b/drivers/block/osdblk.c
index 79aa179..e229425 100644
--- a/drivers/block/osdblk.c
+++ b/drivers/block/osdblk.c
@@ -423,7 +423,7 @@
}
/* 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);
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 983aed1..921a8c8 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -290,7 +290,8 @@
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);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 4c4b732..6f388fd 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -272,7 +272,11 @@
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 @@
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,
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 019e668..e113c75 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -402,6 +402,9 @@
*/
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.
*/
diff --git a/include/scsi/scsi_tcq.h b/include/scsi/scsi_tcq.h
index 9708b28..b27977e 100644
--- a/include/scsi/scsi_tcq.h
+++ b/include/scsi/scsi_tcq.h
@@ -66,7 +66,8 @@
* devices on the shared host (for libata)
*/
if (!shost->bqt) {
- shost->bqt = blk_init_tags(depth);
+ shost->bqt = blk_init_tags(depth,
+ shost->hostt->tag_alloc_policy);
if (!shost->bqt)
return -ENOMEM;
}
