blk-mq: fix tag_get wait task can't be awakened

In case of shared tags, there might be more than one hctx which
allocates from the same tags, and each hctx is limited to allocate at
most:
        hctx_max_depth = max((bt->sb.depth + users - 1) / users, 4U);

tag idle detection is lazy, and may be delayed for 30sec, so there
could be just one real active hctx(queue) but all others are actually
idle and still accounted as active because of the lazy idle detection.
Then if wake_batch is > hctx_max_depth, driver tag allocation may wait
forever on this real active hctx.

Fix this by recalculating wake_batch when inc or dec active_queues.

Fixes: 0d2602ca30e41 ("blk-mq: improve support for shared tags maps")
Suggested-by: Ming Lei <ming.lei@redhat.com>
Suggested-by: John Garry <john.garry@huawei.com>
Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220113025536.1479653-1-qiulaibin@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
index fc0357a6e19b..95df357ec009 100644
--- a/include/linux/sbitmap.h
+++ b/include/linux/sbitmap.h
@@ -416,6 +416,17 @@ static inline void sbitmap_queue_free(struct sbitmap_queue *sbq)
 }
 
 /**
+ * sbitmap_queue_recalculate_wake_batch() - Recalculate wake batch
+ * @sbq: Bitmap queue to recalculate wake batch.
+ * @users: Number of shares.
+ *
+ * Like sbitmap_queue_update_wake_batch(), this will calculate wake batch
+ * by depth. This interface is for HCTX shared tags or queue shared tags.
+ */
+void sbitmap_queue_recalculate_wake_batch(struct sbitmap_queue *sbq,
+					    unsigned int users);
+
+/**
  * sbitmap_queue_resize() - Resize a &struct sbitmap_queue.
  * @sbq: Bitmap queue to resize.
  * @depth: New number of bits to resize to.