From f0276924fa35a3607920a58cf5d878212824b951 Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Tue, 31 Dec 2013 11:38:50 +0800 Subject: blk-mq: Don't reserve a tag for flush request Reserving a tag (request) for flush to avoid dead lock is a overkill. A tag is valuable resource. We can track the number of flush requests and disallow having too many pending flush requests allocated. With this patch, blk_mq_alloc_request_pinned() could do a busy nop (but not a dead loop) if too many pending requests are allocated and new flush request is allocated. But this should not be a problem, too many pending flush requests are very rare case. I verified this can fix the deadlock caused by too many pending flush requests. Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe --- include/linux/blk-mq.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include') diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 161b23105b1e..1e8f16f65af4 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -36,12 +36,15 @@ struct blk_mq_hw_ctx { struct list_head page_list; struct blk_mq_tags *tags; + atomic_t pending_flush; + unsigned long queued; unsigned long run; #define BLK_MQ_MAX_DISPATCH_ORDER 10 unsigned long dispatched[BLK_MQ_MAX_DISPATCH_ORDER]; unsigned int queue_depth; + unsigned int reserved_tags; unsigned int numa_node; unsigned int cmd_size; /* per-request extra data */ -- cgit v1.2.3