[PATCH 2/3] blk-mq: Check queue depth is valid

[Alexander Gordeev]

Ensure that depth of a queue is enough to hold at least
reserved tags plus a minimal amount of normal tags. The
minimal amount is chosen to be consistent with minimal
length of tags cache.

Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxx>
---
 block/blk-mq-tag.c |    8 ++++----
 block/blk-mq-tag.h |    6 ++++++
 block/blk-mq.c     |   12 +++++++-----
 3 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 6718007..fe4acb1 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -447,10 +447,10 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags,
 	tags->nr_tags = nr_tags;
 	tags->reserved_tags = reserved_tags;
 	tags->max_cache = nr_tags / num_possible_cpus();
-	if (tags->max_cache < 4)
-		tags->max_cache = 4;
-	else if (tags->max_cache > 64)
-		tags->max_cache = 64;
+	if (tags->max_cache < BLK_MQ_TAG_CACHE_MIN)
+		tags->max_cache = BLK_MQ_TAG_CACHE_MIN;
+	else if (tags->max_cache > BLK_MQ_TAG_CACHE_MAX)
+		tags->max_cache = BLK_MQ_TAG_CACHE_MAX;
 
 	tags->batch_move = tags->max_cache / 2;
 
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index ce4d5b2..716ea79 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -14,7 +14,13 @@ 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);
 
 enum {
+	BLK_MQ_TAG_CACHE_MIN	= 4,
+	BLK_MQ_TAG_CACHE_MAX	= 64,
+};
+
+enum {
 	BLK_MQ_TAG_FAIL		= -1U,
+	BLK_MQ_TAG_MIN		= BLK_MQ_TAG_CACHE_MIN,
 	BLK_MQ_TAG_MAX		= BLK_MQ_TAG_FAIL - 1,
 };
 
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6fc1df3..a8b4c79 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1151,8 +1151,8 @@ static int blk_mq_init_rq_map(struct blk_mq_hw_ctx *hctx,
 		}
 	}
 
-	if (!i)
-		return -ENOMEM;
+	if (i < (reserved_tags + BLK_MQ_TAG_MIN))
+		goto err_rq_map;
 	else if (i != hctx->queue_depth) {
 		hctx->queue_depth = i;
 		pr_warn("%s: queue depth set to %u because of low memory\n",
@@ -1161,6 +1161,7 @@ static int blk_mq_init_rq_map(struct blk_mq_hw_ctx *hctx,
 
 	hctx->tags = blk_mq_init_tags(hctx->queue_depth, reserved_tags, node);
 	if (!hctx->tags) {
+err_rq_map:
 		blk_mq_free_rq_map(hctx);
 		return -ENOMEM;
 	}
@@ -1305,9 +1306,10 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_reg *reg,
 	struct request_queue *q;
 	int i;
 
-	if (!reg->nr_hw_queues || !reg->ops->queue_rq ||
-	    !reg->ops->map_queue || !reg->ops->alloc_hctx ||
-	    !reg->ops->free_hctx)
+	if (!reg->nr_hw_queues ||
+	    !reg->ops->queue_rq || !reg->ops->map_queue ||
+	    !reg->ops->alloc_hctx || !reg->ops->free_hctx ||
+	    (reg->queue_depth < (reg->reserved_tags + BLK_MQ_TAG_MIN)))
 		return ERR_PTR(-EINVAL);
 
 	if (!reg->queue_depth)
-- 
1.7.7.6


-- 
Regards,
Alexander Gordeev
agordeev@xxxxxxxxxx
--
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