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Sun, 22 Jun 2025 22:13:44 -0400 X-MC-Unique: NSpttJjBP1eRHtCF2tVqTQ-1 X-Mimecast-MFC-AGG-ID: NSpttJjBP1eRHtCF2tVqTQ_1750644823 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7CA9D19560AE; Mon, 23 Jun 2025 02:13:42 +0000 (UTC) Received: from fedora (unknown [10.72.116.88]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 82509195608D; Mon, 23 Jun 2025 02:13:38 +0000 (UTC) Date: Mon, 23 Jun 2025 10:13:33 +0800 From: Ming Lei To: Yoav Cohen Cc: Jens Axboe , "linux-block@vger.kernel.org" , Uday Shankar , Caleb Sander Mateos Subject: Re: [PATCH 2/3] ublk: add feature UBLK_F_QUIESCE Message-ID: References: <20250522163523.406289-1-ming.lei@redhat.com> <20250522163523.406289-3-ming.lei@redhat.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 On Thu, Jun 12, 2025 at 12:04:39PM +0000, Yoav Cohen wrote: > > Hi Ming, > > So I know it's a radical situation but my only concern is that: > > 0) On our application timeout of IO may be set to few minutes as it is goes over the network. > 1) Let's assume we have 1 queue with QD=1. > 2) the Only IO is in the userspace application but as we send the IOs over the network it may be stuck due to connectivy issues. > 3) User trying to upgrade/stop the application so we issue Quiesce_DEV with infinite timeout as we want to ensure it works. > 4) We are stuck now until network connection will recover or Our datapath will somehow Issue the COMMIT_AND_FETCH back to to the kernel so it we can get the ABORT later and QUICESE_DEV can finish. > > Problem is that I don't want to wait for this IO until recovery but on the other end I don't want to complete the IO with error to the user. > So on this case I guess we can abort the application or something but maybe it will be cleaner that on Quiesce_DEV will need to issue another SQE per queue or something so we can notify the application this way about it. > > Anyway also on our case it will be super rare to happen where there is a queue without an idle operation + network is currently down but we try to be complete as possible. > What do you think? Hi Yoav, The multishot approach for fetching io command should address the issue wrt. single queue depth case: https://github.com/ming1/linux/commits/ublk2-cmd-batch.v3/ In which there is always one multishot FETCH_IO_CMDS for notifying ublk server for new io commands(requests) in batch way. Thanks, Ming