From 01e99aeca3979600302913cef3f89076786f32c8 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Tue, 25 Feb 2020 09:04:32 +0800 Subject: 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 Cc: Christoph Hellwig Cc: Ewan D. Milne Signed-off-by: Ming Lei Signed-off-by: Jens Axboe --- block/blk-flush.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'block/blk-flush.c') diff --git a/block/blk-flush.c b/block/blk-flush.c index 3f977c517960..5cc775bdb06a 100644 --- a/block/blk-flush.c +++ b/block/blk-flush.c @@ -412,7 +412,7 @@ void blk_insert_flush(struct request *rq) */ if ((policy & REQ_FSEQ_DATA) && !(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) { - blk_mq_request_bypass_insert(rq, false); + blk_mq_request_bypass_insert(rq, false, false); return; } -- cgit v1.2.3