blk-mq: Shared tag enhancements

Storage controllers may expose multiple block devices that share hardware
resources managed by blk-mq. This patch enhances the shared tags so a
low-level driver can access the shared resources not tied to the unshared
h/w contexts. This way the LLD can dynamically add and delete disks and
request queues without having to track all the request_queue hctx's to
iterate outstanding tags.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index be3290cc0644..9b6e28830b82 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -438,6 +438,39 @@ static void bt_for_each(struct blk_mq_hw_ctx *hctx,
         }
 }
 
+static void bt_tags_for_each(struct blk_mq_tags *tags,
+                struct blk_mq_bitmap_tags *bt, unsigned int off,
+                busy_tag_iter_fn *fn, void *data, bool reserved)
+{
+        struct request *rq;
+        int bit, i;
+
+        if (!tags->rqs)
+                return;
+        for (i = 0; i < bt->map_nr; i++) {
+                struct blk_align_bitmap *bm = &bt->map[i];
+
+                for (bit = find_first_bit(&bm->word, bm->depth);
+                     bit < bm->depth;
+                     bit = find_next_bit(&bm->word, bm->depth, bit + 1)) {
+                        rq = blk_mq_tag_to_rq(tags, off + bit);
+                        fn(rq, data, reserved);
+                }
+
+                off += (1 << bt->bits_per_word);
+        }
+}
+
+void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn,
+                void *priv)
+{
+        if (tags->nr_reserved_tags)
+                bt_tags_for_each(tags, &tags->breserved_tags, 0, fn, priv, true);
+        bt_tags_for_each(tags, &tags->bitmap_tags, tags->nr_reserved_tags, fn, priv,
+                        false);
+}
+EXPORT_SYMBOL(blk_mq_all_tag_busy_iter);
+
 void blk_mq_tag_busy_iter(struct blk_mq_hw_ctx *hctx, busy_iter_fn *fn,
                 void *priv)
 {
@@ -580,6 +613,11 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
         if (!tags)
                 return NULL;
 
+        if (!zalloc_cpumask_var(&tags->cpumask, GFP_KERNEL)) {
+                kfree(tags);
+                return NULL;
+        }
+
         tags->nr_tags = total_tags;
         tags->nr_reserved_tags = reserved_tags;