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authorShaohua Li <shli@kernel.org>2013-12-31 11:38:50 +0800
committerJens Axboe <axboe@kernel.dk>2014-01-30 12:57:25 -0700
commitf0276924fa35a3607920a58cf5d878212824b951 (patch)
tree5759cef09f3ba6b2f206ace779fef298a8b9d7be /include
parentd835502f3dacad1638d516ab156d66f0ba377cf5 (diff)
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 <shli@fusionio.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include')
-rw-r--r--include/linux/blk-mq.h3
1 files changed, 3 insertions, 0 deletions
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 */