blk-mq: add tag allocation policy

This is the blk-mq part to support tag allocation policy. The default
allocation policy isn't changed (though it's not a strict FIFO). The new
policy is round-robin for libata. But it's a try-best implementation. If
multiple tasks are competing, the tags returned will be mixed (which is
unavoidable even with !mq, as requests from different tasks can be
mixed in queue)

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-mq-tag.c b/block/blk-mq-tag.c
index d4daee385a235ebd7c8bb86c3ecbaef74e46f233..e3387a74a9a2e63134512f7dd521266d61181115 100644 (file)
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -140,7 +140,8 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
        return atomic_read(&hctx->nr_active) < depth;
 }
 
-static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)
+static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag,
+                        bool nowrap)
 {
        int tag, org_last_tag = last_tag;
 
@@ -152,7 +153,7 @@ static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)
                         * offset to 0 in a failure case, so start from 0 to
                         * exhaust the map.
                         */
-                       if (org_last_tag && last_tag) {
+                       if (org_last_tag && last_tag && !nowrap) {
                                last_tag = org_last_tag = 0;
                                continue;
                        }
@@ -170,6 +171,8 @@ static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)
        return tag;
 }
 
+#define BT_ALLOC_RR(tags) (tags->alloc_policy == BLK_TAG_ALLOC_RR)
+
 /*
  * Straight forward bitmap tag implementation, where each bit is a tag
  * (cleared == free, and set == busy). The small twist is using per-cpu
@@ -182,7 +185,7 @@ static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)
  * until the map is exhausted.
  */
 static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt,
-                   unsigned int *tag_cache)
+                   unsigned int *tag_cache, struct blk_mq_tags *tags)
 {
        unsigned int last_tag, org_last_tag;
        int index, i, tag;
@@ -194,7 +197,8 @@ static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt,
        index = TAG_TO_INDEX(bt, last_tag);
 
        for (i = 0; i < bt->map_nr; i++) {
-               tag = __bt_get_word(&bt->map[index], TAG_TO_BIT(bt, last_tag));
+               tag = __bt_get_word(&bt->map[index], TAG_TO_BIT(bt, last_tag),
+                                   BT_ALLOC_RR(tags));
                if (tag != -1) {
                        tag += (index << bt->bits_per_word);
                        goto done;
@@ -221,7 +225,7 @@ static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt,
         * up using the specific cached tag.
         */
 done:
-       if (tag == org_last_tag) {
+       if (tag == org_last_tag || unlikely(BT_ALLOC_RR(tags))) {
                last_tag = tag + 1;
                if (last_tag >= bt->depth - 1)
                        last_tag = 0;
@@ -250,13 +254,13 @@ static struct bt_wait_state *bt_wait_ptr(struct blk_mq_bitmap_tags *bt,
 static int bt_get(struct blk_mq_alloc_data *data,
                struct blk_mq_bitmap_tags *bt,
                struct blk_mq_hw_ctx *hctx,
-               unsigned int *last_tag)
+               unsigned int *last_tag, struct blk_mq_tags *tags)
 {
        struct bt_wait_state *bs;
        DEFINE_WAIT(wait);
        int tag;
 
-       tag = __bt_get(hctx, bt, last_tag);
+       tag = __bt_get(hctx, bt, last_tag, tags);
        if (tag != -1)
                return tag;
 
@@ -267,7 +271,7 @@ static int bt_get(struct blk_mq_alloc_data *data,
        do {
                prepare_to_wait(&bs->wait, &wait, TASK_UNINTERRUPTIBLE);
 
-               tag = __bt_get(hctx, bt, last_tag);
+               tag = __bt_get(hctx, bt, last_tag, tags);
                if (tag != -1)
                        break;
 
@@ -282,7 +286,7 @@ static int bt_get(struct blk_mq_alloc_data *data,
                 * Retry tag allocation after running the hardware queue,
                 * as running the queue may also have found completions.
                 */
-               tag = __bt_get(hctx, bt, last_tag);
+               tag = __bt_get(hctx, bt, last_tag, tags);
                if (tag != -1)
                        break;
 
@@ -313,7 +317,7 @@ static unsigned int __blk_mq_get_tag(struct blk_mq_alloc_data *data)
        int tag;
 
        tag = bt_get(data, &data->hctx->tags->bitmap_tags, data->hctx,
-                       &data->ctx->last_tag);
+                       &data->ctx->last_tag, data->hctx->tags);
        if (tag >= 0)
                return tag + data->hctx->tags->nr_reserved_tags;
 
@@ -329,7 +333,8 @@ static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_alloc_data *data)
                return BLK_MQ_TAG_FAIL;
        }
 
-       tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL, &zero);
+       tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL, &zero,
+               data->hctx->tags);
        if (tag < 0)
                return BLK_MQ_TAG_FAIL;
 
@@ -401,7 +406,8 @@ void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag,
 
                BUG_ON(real_tag >= tags->nr_tags);
                bt_clear_tag(&tags->bitmap_tags, real_tag);
-               *last_tag = real_tag;
+               if (likely(tags->alloc_policy == BLK_TAG_ALLOC_FIFO))
+                       *last_tag = real_tag;
        } else {
                BUG_ON(tag >= tags->nr_reserved_tags);
                bt_clear_tag(&tags->breserved_tags, tag);
@@ -538,10 +544,12 @@ static void bt_free(struct blk_mq_bitmap_tags *bt)
 }
 
 static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
-                                                  int node)
+                                                  int node, int alloc_policy)
 {
        unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
 
+       tags->alloc_policy = alloc_policy;
+
        if (bt_alloc(&tags->bitmap_tags, depth, node, false))
                goto enomem;
        if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, node, true))
@@ -555,7 +563,8 @@ enomem:
 }
 
 struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
-                                    unsigned int reserved_tags, int node)
+                                    unsigned int reserved_tags,
+                                    int node, int alloc_policy)
 {
        struct blk_mq_tags *tags;
 
@@ -571,7 +580,7 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
        tags->nr_tags = total_tags;
        tags->nr_reserved_tags = reserved_tags;
 
-       return blk_mq_init_bitmap_tags(tags, node);
+       return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
 }
 
 void blk_mq_free_tags(struct blk_mq_tags *tags)

diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index a6fa0fc9d41a2e91c8bb4ce29bb2b1a0d952c8ed..90767b370308daab9bdd7efe3903dd72af2a6dad 100644 (file)
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -42,10 +42,12 @@ struct blk_mq_tags {
 
        struct request **rqs;
        struct list_head page_list;
+
+       int alloc_policy;
 };
 
 
-extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int reserved_tags, int node);
+extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int reserved_tags, int node, int alloc_policy);
 extern void blk_mq_free_tags(struct blk_mq_tags *tags);
 
 extern unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data);

diff --git a/block/blk-mq.c b/block/blk-mq.c
index a7d4a988516f173e8f942a183e815bc1e33ea602..eb8e694fda0655cd9fb858c268336fb5a58f0e68 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1374,7 +1374,8 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set,
        size_t rq_size, left;
 
        tags = blk_mq_init_tags(set->queue_depth, set->reserved_tags,
-                               set->numa_node);
+                               set->numa_node,
+                               BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags));
        if (!tags)
                return NULL;
 

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 9ea95dd3e2604eea2613a5a15d074c2357fac7dd..49ab11508286ba55db17f5ce1a5ba6115eb7b627 100644 (file)
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2188,6 +2188,8 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
        shost->tag_set.cmd_size = cmd_size;
        shost->tag_set.numa_node = NUMA_NO_NODE;
        shost->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_SG_MERGE;
+       shost->tag_set.flags |=
+               BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy);
        shost->tag_set.driver_data = shost;
 
        return blk_mq_alloc_tag_set(&shost->tag_set);

diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 5b6500c77ed2deec2fb87cdb5a51239da4d73be6..86b08b1a5eba67ae5be654d0a298c31e96963e9b 100644 (file)
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -147,6 +147,8 @@ enum {
        BLK_MQ_F_SG_MERGE       = 1 << 2,
        BLK_MQ_F_SYSFS_UP       = 1 << 3,
        BLK_MQ_F_DEFER_ISSUE    = 1 << 4,
+       BLK_MQ_F_ALLOC_POLICY_START_BIT = 8,
+       BLK_MQ_F_ALLOC_POLICY_BITS = 1,
 
        BLK_MQ_S_STOPPED        = 0,
        BLK_MQ_S_TAG_ACTIVE     = 1,
@@ -155,6 +157,12 @@ enum {
 
        BLK_MQ_CPU_WORK_BATCH   = 8,
 };
+#define BLK_MQ_FLAG_TO_ALLOC_POLICY(flags) \
+       ((flags >> BLK_MQ_F_ALLOC_POLICY_START_BIT) & \
+               ((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1))
+#define BLK_ALLOC_POLICY_TO_MQ_FLAG(policy) \
+       ((policy & ((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1)) \
+               << BLK_MQ_F_ALLOC_POLICY_START_BIT)
 
 struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *);
 void blk_mq_finish_init(struct request_queue *q);