From: Christoph Hellwig <firstname.lastname@example.org> To: Ming Lei <email@example.com> Cc: Jens Axboe <firstname.lastname@example.org>, email@example.com Subject: Re: [PATCH] blk-mq: insert passthrough request into hctx->dispatch directly Date: Wed, 19 Feb 2020 08:36:15 -0800 Message-ID: <20200219163615.GE18377@infradead.org> (raw) In-Reply-To: <firstname.lastname@example.org> On Sat, Feb 15, 2020 at 11:21:40AM +0800, Ming Lei wrote: > 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. > > Fix this issue by inserting passthrough request into hctx->dispatch > directly. Then it becomes consistent with original legacy IO request > path, in which passthrough request is always added to q->queue_head. Do you have a description of an actual problem this fixes? Maybe even a reproducer for blktests?
next prev parent reply index Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-02-15 3:21 Ming Lei 2020-02-19 16:36 ` Christoph Hellwig [this message] 2020-02-19 22:10 ` Ming Lei 2020-02-19 23:47 ` dongli.zhang 2020-02-20 1:45 ` Ming Lei 2020-02-20 3:11 ` Dongli Zhang
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