blk-mq: split out tag initialization, support shared tags

Add a new blk_mq_tag_set structure that gets set up before we initialize
the queue.  A single blk_mq_tag_set structure can be shared by multiple
queues.

Signed-off-by: Christoph Hellwig <hch@lst.de>

Modular export of blk_mq_{alloc,free}_tagset added by me.

Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-mq-cpumap.c

@@ -80,17 +80,17 @@ int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues)
  return 0;
 }
 
-unsigned int *blk_mq_make_queue_map(struct blk_mq_reg *reg)
+unsigned int *blk_mq_make_queue_map(struct blk_mq_tag_set *set)
 {
  unsigned int *map;
 
  /* If cpus are offline, map them to first hctx */
  map = kzalloc_node(sizeof(*map) * num_possible_cpus(), GFP_KERNEL,
- reg->numa_node);
+ set->numa_node);
  if (!map)
  return NULL;
 
- if (!blk_mq_update_queue_map(map, reg->nr_hw_queues))
+ if (!blk_mq_update_queue_map(map, set->nr_hw_queues))
  return map;
 
  kfree(map);

block/blk-mq-tag.c

@@ -1,25 +1,11 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
-#include <linux/percpu_ida.h>
 
 #include <linux/blk-mq.h>
 #include "blk.h"
 #include "blk-mq.h"
 #include "blk-mq-tag.h"
 
-/*
- * Per tagged queue (tag address space) map
- */
-struct blk_mq_tags {
- unsigned int nr_tags;
- unsigned int nr_reserved_tags;
- unsigned int nr_batch_move;
- unsigned int nr_max_cache;
-
- struct percpu_ida free_tags;
- struct percpu_ida reserved_tags;
-};
-
 void blk_mq_wait_for_tags(struct blk_mq_tags *tags)
 {
  int tag = blk_mq_get_tag(tags, __GFP_WAIT, false);

block/blk-mq-tag.h

@@ -1,7 +1,24 @@
 #ifndef INT_BLK_MQ_TAG_H
 #define INT_BLK_MQ_TAG_H
 
-struct blk_mq_tags;
+#include <linux/percpu_ida.h>
+
+/*
+ * Tag address space map.
+ */
+struct blk_mq_tags {
+ unsigned int nr_tags;
+ unsigned int nr_reserved_tags;
+ unsigned int nr_batch_move;
+ unsigned int nr_max_cache;
+
+ struct percpu_ida free_tags;
+ struct percpu_ida reserved_tags;
+
+ struct request **rqs;
+ struct list_head page_list;
+};
+
 
 extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int reserved_tags, int node);
 extern void blk_mq_free_tags(struct blk_mq_tags *tags);