---
 block/blk-mq-tag.c     |    2 ++
 block/blk-mq.c         |   83 +++++++++++++++++++++++++++++++++++++++++++-----
 block/blk-mq.h         |    2 ++
 include/linux/blk-mq.h |   12 +++++++
 4 files changed, 91 insertions(+), 8 deletions(-)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 108f82b..a7b1888 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -121,6 +121,8 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int 
total_tags,
        if (!tags)
                return NULL;
 
+       kref_init(&tags->ref_count);
+
        nr_tags = total_tags - reserved_tags;
        nr_cache = nr_tags / num_possible_cpus();
 
diff --git a/block/blk-mq.c b/block/blk-mq.c
index f1b5d52..3d63d71 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1051,8 +1051,10 @@ void blk_mq_free_commands(struct request_queue *q,
 }
 EXPORT_SYMBOL(blk_mq_free_commands);
 
-static void blk_mq_free_rq_map(struct blk_mq_tags *tags)
+static void blk_mq_free_rq_map(struct kref *kref)
 {
+       struct blk_mq_tags *tags =
+               container_of(kref, struct blk_mq_tags, ref_count);
        struct page *page;
 
        while (!list_empty(&tags->page_list)) {
@@ -1066,6 +1068,17 @@ static void blk_mq_free_rq_map(struct blk_mq_tags *tags)
        blk_mq_free_tags(tags);
 }
 
+static void blk_mq_put_rq_map(struct blk_mq_tags *tags)
+{
+       kref_put(&tags->ref_count, blk_mq_free_rq_map);
+}
+
+static struct blk_mq_tags *blk_mq_get_rq_map(struct blk_mq_tags *tags)
+{
+       kref_get(&tags->ref_count);
+       return tags;
+}
+
 static size_t order_to_size(unsigned int order)
 {
        size_t ret = PAGE_SIZE;
@@ -1144,7 +1157,7 @@ static struct blk_mq_tags *blk_mq_init_rq_map(unsigned 
int total_tags,
 
 fail:
        pr_warn("%s: failed to allocate requests\n", __func__);
-       blk_mq_free_rq_map(tags);
+       blk_mq_put_rq_map(tags);
        return NULL;
 }
 
@@ -1178,10 +1191,14 @@ static int blk_mq_init_hw_queues(struct request_queue 
*q,
                                                blk_mq_hctx_notify, hctx);
                blk_mq_register_cpu_notifier(&hctx->cpu_notifier);
 
-               hctx->tags = blk_mq_init_rq_map(hctx->queue_depth,
-                               reg->reserved_tags, reg->cmd_size, node);
-               if (!hctx->tags)
-                       break;
+               if (reg->shared_tags) {
+                       hctx->tags = 
blk_mq_get_rq_map(reg->shared_tags->tags[i]);
+               } else {
+                       hctx->tags = blk_mq_init_rq_map(hctx->queue_depth,
+                                       reg->reserved_tags, reg->cmd_size, 
node);
+                       if (!hctx->tags)
+                               break;
+               }
 
                /*
                 * Allocate space for all possible cpus to avoid allocation in
@@ -1221,7 +1238,7 @@ static int blk_mq_init_hw_queues(struct request_queue *q,
 
                blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
                if (hctx->tags)
-                       blk_mq_free_rq_map(hctx->tags);
+                       blk_mq_put_rq_map(hctx->tags);
                kfree(hctx->ctxs);
        }
 
@@ -1399,7 +1416,7 @@ void blk_mq_free_queue(struct request_queue *q)
                kfree(hctx->ctx_map);
                kfree(hctx->ctxs);
                if (hctx->tags)
-                       blk_mq_free_rq_map(hctx->tags);
+                       blk_mq_put_rq_map(hctx->tags);
                blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
                if (q->mq_ops->exit_hctx)
                        q->mq_ops->exit_hctx(hctx, i);
@@ -1459,6 +1476,56 @@ static int blk_mq_queue_reinit_notify(struct 
notifier_block *nb,
        return NOTIFY_OK;
 }
 
+struct blk_mq_shared_tags *blk_mq_alloc_shared_tags(struct blk_mq_reg *reg,
+               int (*init)(void *, struct request *), void *data)
+{
+       struct blk_mq_shared_tags *shared_tags;
+       int i, j;
+
+       shared_tags = kmalloc_node(sizeof(*shared_tags) +
+                               reg->nr_hw_queues * sizeof(struct blk_mq_tags),
+                               GFP_KERNEL, reg->numa_node);
+       if (!shared_tags)
+               goto out;
+
+       shared_tags->nr_hw_queues = reg->nr_hw_queues;
+       shared_tags->queue_depth = reg->queue_depth;
+       for (i = 0; i < reg->nr_hw_queues; i++) {
+               shared_tags->tags[i] = blk_mq_init_rq_map(reg->queue_depth,
+                               reg->reserved_tags, reg->cmd_size, 
reg->numa_node);
+               if (!shared_tags->tags[i])
+                       goto out_unwind;
+
+               for (j = 0; j < reg->queue_depth; j++) {
+                       struct request *rq = shared_tags->tags[i]->rqs[j];
+                       int ret;
+
+                       ret = init(data, rq);
+                       BUG_ON(ret);
+               }
+       }
+
+       return shared_tags;
+
+out_unwind:
+       while (--i >= 0)
+               blk_mq_put_rq_map(shared_tags->tags[i]);
+out:
+       return NULL;
+}
+
+void blk_mq_free_shared_tags(struct blk_mq_shared_tags *shared_tags,
+               void (*exit)(void *, struct request *), void *data)
+{
+       int i, j;
+
+       for (i = 0; i < shared_tags->nr_hw_queues; i++) {
+               for (j = 0; j < shared_tags->queue_depth; j++)
+                       exit(data, shared_tags->tags[i]->rqs[j]);
+               blk_mq_put_rq_map(shared_tags->tags[i]);
+       }
+}
+
 void blk_mq_disable_hotplug(void)
 {
        mutex_lock(&all_q_mutex);
diff --git a/block/blk-mq.h b/block/blk-mq.h
index eca3a47..d7c753b 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -17,6 +17,8 @@ struct blk_mq_tags {
 
        struct request **rqs;
        struct list_head page_list;
+
+       struct kref ref_count;
 };
 
 struct blk_mq_ctx {
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 69aa3ad..a564167 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -47,6 +47,12 @@ struct blk_mq_hw_ctx {
        struct kobject          kobj;
 };
 
+struct blk_mq_shared_tags {
+       unsigned int            nr_hw_queues;
+       unsigned int            queue_depth;
+       struct blk_mq_tags      *tags[];
+};
+
 struct blk_mq_reg {
        struct blk_mq_ops       *ops;
        unsigned int            nr_hw_queues;
@@ -56,6 +62,7 @@ struct blk_mq_reg {
        int                     numa_node;
        unsigned int            timeout;
        unsigned int            flags;          /* BLK_MQ_F_* */
+       struct blk_mq_shared_tags *shared_tags;
 };
 
 typedef int (queue_rq_fn)(struct blk_mq_hw_ctx *, struct request *);
@@ -118,6 +125,11 @@ void blk_mq_unregister_disk(struct gendisk *);
 int blk_mq_init_commands(struct request_queue *, int (*init)(void *data, 
struct blk_mq_hw_ctx *, struct request *, unsigned int), void *data);
 void blk_mq_free_commands(struct request_queue *, void (*free)(void *data, 
struct blk_mq_hw_ctx *, struct request *, unsigned int), void *data);
 
+struct blk_mq_shared_tags *blk_mq_alloc_shared_tags(struct blk_mq_reg *reg,
+               int (*init)(void *, struct request *), void *data);
+void blk_mq_free_shared_tags(struct blk_mq_shared_tags *shared_tags,
+               void (*exit)(void *, struct request *), void *data);
+
 void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule);
 
 void blk_mq_insert_request(struct request *, bool, bool, bool);
-- 
1.7.10.4

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