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authorMing Lei <ming.lei@redhat.com>2020-02-25 09:04:32 +0800
committerJens Axboe <axboe@kernel.dk>2020-02-24 18:50:48 -0700
commit01e99aeca3979600302913cef3f89076786f32c8 (patch)
treefd971e355c8d579a32d0689755870b498d3b2b11 /block/blk-mq.h
parentf8788d86ab28f61f7b46eb6be375f8a726783636 (diff)
blk-mq: insert passthrough request into hctx->dispatch directly
For some reason, device may be in one situation which can't handle FS request, so STS_RESOURCE is always returned and the FS request will be added to hctx->dispatch. However passthrough request may be required at that time for fixing the problem. If passthrough request is added to scheduler queue, there isn't any chance for blk-mq to dispatch it given we prioritize requests in hctx->dispatch. Then the FS IO request may never be completed, and IO hang is caused. So passthrough request has to be added to hctx->dispatch directly for fixing the IO hang. Fix this issue by inserting passthrough request into hctx->dispatch directly together withing adding FS request to the tail of hctx->dispatch in blk_mq_dispatch_rq_list(). Actually we add FS request to tail of hctx->dispatch at default, see blk_mq_request_bypass_insert(). Then it becomes consistent with original legacy IO request path, in which passthrough request is always added to q->queue_head. Cc: Dongli Zhang <dongli.zhang@oracle.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Ewan D. Milne <emilne@redhat.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-mq.h')
-rw-r--r--block/blk-mq.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/block/blk-mq.h b/block/blk-mq.h
index eaaca8fc1c28..c0fa34378eb2 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -66,7 +66,8 @@ int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
*/
void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
bool at_head);
-void blk_mq_request_bypass_insert(struct request *rq, bool run_queue);
+void blk_mq_request_bypass_insert(struct request *rq, bool at_head,
+ bool run_queue);
void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
struct list_head *list);