On Wed, Jan 11, 2017 at 02:39:59PM -0700, Jens Axboe wrote:
> This is in preparation for having another tag set available. Cleanup
> the parameters, and allow passing in of tags fo blk_mq_put_tag().

I've been playing around with this are a bit but never submitted
anything.  Below is an untested merge of my previous bits with your
patch, let me know what you think about it:

---
>From c9ea92bfb468e9116149db95d246e48ace2b87f1 Mon Sep 17 00:00:00 2001
From: Jens Axboe <ax...@fb.com>
Date: Wed, 11 Jan 2017 11:04:53 -0700
Subject: blk-mq-tag: cleanup the normal/reserved tag allocation

This is in preparation for having another tag set available. Cleanup
the parameters, and allow passing in of tags for blk_mq_put_tag().

Signed-off-by: Jens Axboe <ax...@fb.com>
[hch: even more cleanups]
Signed-off-by: Christoph Hellwig <h...@lst.de>
---
 block/blk-mq-tag.c | 94 +++++++++++++++++++++---------------------------------
 block/blk-mq-tag.h |  4 +--
 block/blk-mq.c     |  2 +-
 block/blk-mq.h     |  5 +++
 4 files changed, 44 insertions(+), 61 deletions(-)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index dcf5ce3..ced7527 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -90,32 +90,46 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx 
*hctx,
        return atomic_read(&hctx->nr_active) < depth;
 }
 
-static int __bt_get(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt)
+static int __blk_mq_get_tag(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue 
*bt)
 {
        if (!hctx_may_queue(hctx, bt))
                return -1;
        return __sbitmap_queue_get(bt);
 }
 
-static int bt_get(struct blk_mq_alloc_data *data, struct sbitmap_queue *bt,
-                 struct blk_mq_hw_ctx *hctx, struct blk_mq_tags *tags)
+unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
 {
+       struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
+       struct sbitmap_queue *bt;
        struct sbq_wait_state *ws;
        DEFINE_WAIT(wait);
+       unsigned int tag_offset;
        int tag;
 
-       tag = __bt_get(hctx, bt);
+       if (data->flags & BLK_MQ_REQ_RESERVED) {
+               if (unlikely(!tags->nr_reserved_tags)) {
+                       WARN_ON_ONCE(1);
+                       return BLK_MQ_TAG_FAIL;
+               }
+               bt = &tags->breserved_tags;
+               tag_offset = 0;
+       } else {
+               bt = &tags->bitmap_tags;
+               tag_offset = tags->nr_reserved_tags;
+       }
+
+       tag = __blk_mq_get_tag(data->hctx, bt);
        if (tag != -1)
-               return tag;
+               goto found_tag;
 
        if (data->flags & BLK_MQ_REQ_NOWAIT)
-               return -1;
+               return BLK_MQ_TAG_FAIL;
 
-       ws = bt_wait_ptr(bt, hctx);
+       ws = bt_wait_ptr(bt, data->hctx);
        do {
                prepare_to_wait(&ws->wait, &wait, TASK_UNINTERRUPTIBLE);
 
-               tag = __bt_get(hctx, bt);
+               tag = __blk_mq_get_tag(data->hctx, bt);
                if (tag != -1)
                        break;
 
@@ -125,14 +139,14 @@ static int bt_get(struct blk_mq_alloc_data *data, struct 
sbitmap_queue *bt,
                 * some to complete. Note that hctx can be NULL here for
                 * reserved tag allocation.
                 */
-               if (hctx)
-                       blk_mq_run_hw_queue(hctx, false);
+               if (data->hctx)
+                       blk_mq_run_hw_queue(data->hctx, false);
 
                /*
                 * Retry tag allocation after running the hardware queue,
                 * as running the queue may also have found completions.
                 */
-               tag = __bt_get(hctx, bt);
+               tag = __blk_mq_get_tag(data->hctx, bt);
                if (tag != -1)
                        break;
 
@@ -142,61 +156,25 @@ static int bt_get(struct blk_mq_alloc_data *data, struct 
sbitmap_queue *bt,
 
                data->ctx = blk_mq_get_ctx(data->q);
                data->hctx = blk_mq_map_queue(data->q, data->ctx->cpu);
-               if (data->flags & BLK_MQ_REQ_RESERVED) {
-                       bt = &data->hctx->tags->breserved_tags;
-               } else {
-                       hctx = data->hctx;
-                       bt = &hctx->tags->bitmap_tags;
-               }
+               tags = blk_mq_tags_from_data(data);
+               if (data->flags & BLK_MQ_REQ_RESERVED)
+                       bt = &tags->breserved_tags;
+               else
+                       bt = &tags->bitmap_tags;
+
                finish_wait(&ws->wait, &wait);
-               ws = bt_wait_ptr(bt, hctx);
+               ws = bt_wait_ptr(bt, data->hctx);
        } while (1);
 
        finish_wait(&ws->wait, &wait);
-       return tag;
-}
-
-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->hctx->tags);
-       if (tag >= 0)
-               return tag + data->hctx->tags->nr_reserved_tags;
-
-       return BLK_MQ_TAG_FAIL;
-}
-
-static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_alloc_data *data)
-{
-       int tag;
 
-       if (unlikely(!data->hctx->tags->nr_reserved_tags)) {
-               WARN_ON_ONCE(1);
-               return BLK_MQ_TAG_FAIL;
-       }
-
-       tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL,
-                    data->hctx->tags);
-       if (tag < 0)
-               return BLK_MQ_TAG_FAIL;
-
-       return tag;
+found_tag:
+       return tag + tag_offset;
 }
 
-unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
+void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_tags *tags,
+                   struct blk_mq_ctx *ctx, unsigned int tag)
 {
-       if (data->flags & BLK_MQ_REQ_RESERVED)
-               return __blk_mq_get_reserved_tag(data);
-       return __blk_mq_get_tag(data);
-}
-
-void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
-                   unsigned int tag)
-{
-       struct blk_mq_tags *tags = hctx->tags;
-
        if (tag >= tags->nr_reserved_tags) {
                const int real_tag = tag - tags->nr_reserved_tags;
 
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index d166273..923602d 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -24,8 +24,8 @@ extern struct blk_mq_tags *blk_mq_init_tags(unsigned int 
nr_tags, unsigned int r
 extern void blk_mq_free_tags(struct blk_mq_tags *tags);
 
 extern unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data);
-extern void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
-                          unsigned int tag);
+extern void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_tags 
*tags,
+                          struct blk_mq_ctx *ctx, unsigned int tag);
 extern bool blk_mq_has_free_tags(struct blk_mq_tags *tags);
 extern ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page);
 extern int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int 
depth);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9fc5217..6fab8e9 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -335,7 +335,7 @@ void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx, 
struct blk_mq_ctx *ctx,
 
        clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
        clear_bit(REQ_ATOM_POLL_SLEPT, &rq->atomic_flags);
-       blk_mq_put_tag(hctx, ctx, tag);
+       blk_mq_put_tag(hctx, hctx->tags, ctx, tag);
        blk_queue_exit(q);
 }
 
diff --git a/block/blk-mq.h b/block/blk-mq.h
index e59f5ca..48b7771 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -118,6 +118,11 @@ static inline void blk_mq_set_alloc_data(struct 
blk_mq_alloc_data *data,
        data->hctx = hctx;
 }
 
+static inline struct blk_mq_tags *blk_mq_tags_from_data(struct 
blk_mq_alloc_data *data)
+{
+       return data->hctx->tags;
+}
+
 /*
  * Internal helpers for request allocation/init/free
  */
-- 
2.1.4

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