From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.proxmox.com (Postfix) with ESMTPS id F389469C61 for ; Wed, 28 Jul 2021 12:56:00 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id E3B9923AEC for ; Wed, 28 Jul 2021 12:56:00 +0200 (CEST) Received: from proxmox-new.maurer-it.com (proxmox-new.maurer-it.com [94.136.29.106]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by firstgate.proxmox.com (Proxmox) with ESMTPS id 4C7BE23AE1 for ; Wed, 28 Jul 2021 12:55:59 +0200 (CEST) Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 1CB0542B3F for ; Wed, 28 Jul 2021 12:55:59 +0200 (CEST) From: Fabian Ebner To: pve-devel@lists.proxmox.com Date: Wed, 28 Jul 2021 12:55:55 +0200 Message-Id: <20210728105555.1225184-1-f.ebner@proxmox.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SPAM-LEVEL: Spam detection results: 0 AWL 0.468 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record URIBL_BLOCKED 0.001 ADMINISTRATOR NOTICE: The query to URIBL was blocked. See http://wiki.apache.org/spamassassin/DnsBlocklists#dnsbl-block for more information. [proxmox.com, nongnu.org] Subject: [pve-devel] [PATCH qemu] block/io_uring: resubmit when result is -EAGAIN X-BeenThere: pve-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox VE development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 28 Jul 2021 10:56:01 -0000 Quoting from [0]: Some setups, like SCSI, can throw spurious -EAGAIN off the softirq completion path. Normally we expect this to happen inline as part of submission, but apparently SCSI has a weird corner case where it can happen as part of normal completions. Host kernels without patch [0] can panic when this happens [1], and resubmitting makes the panic more likely. On the other hand, for kernels with patch [0], resubmitting ensures that a block job is not aborted just because of such spurious errors. In particular, this should fix the problem reported in [2] with PBS backups of LVM-backed VMs. [0]: https://lore.kernel.org/io-uring/20210727165811.284510-3-axboe@kernel.dk/T/#u [1]: #9 [ffffb732000c8b70] asm_exc_page_fault at ffffffffa4800ade #10 [ffffb732000c8bf8] io_prep_async_work at ffffffffa3d89c16 #11 [ffffb732000c8c50] io_rw_reissue at ffffffffa3d8b2e1 #12 [ffffb732000c8c78] io_complete_rw at ffffffffa3d8baa8 #13 [ffffb732000c8c98] blkdev_bio_end_io at ffffffffa3d62a80 #14 [ffffb732000c8cc8] bio_endio at ffffffffa3f4e800 #15 [ffffb732000c8ce8] dec_pending at ffffffffa432f854 #16 [ffffb732000c8d30] clone_endio at ffffffffa433170c #17 [ffffb732000c8d70] bio_endio at ffffffffa3f4e800 #18 [ffffb732000c8d90] blk_update_request at ffffffffa3f53a37 #19 [ffffb732000c8dd0] scsi_end_request at ffffffffa4233a5c #20 [ffffb732000c8e08] scsi_io_completion at ffffffffa423432c #21 [ffffb732000c8e58] scsi_finish_command at ffffffffa422c527 #22 [ffffb732000c8e88] scsi_softirq_done at ffffffffa42341e4 [2]: https://forum.proxmox.com/threads/backup-job-failed-with-err-11-on-2-of-6-vms.92568/ Signed-off-by: Fabian Ebner --- Mail sent upstream: https://lists.nongnu.org/archive/html/qemu-devel/2021-07/msg06765.html block/io_uring.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/io_uring.c b/block/io_uring.c index 00a3ee9fb8..77d162cb24 100644 --- a/block/io_uring.c +++ b/block/io_uring.c @@ -165,7 +165,7 @@ static void luring_process_completions(LuringState *s) total_bytes = ret + luringcb->total_read; if (ret < 0) { - if (ret == -EINTR) { + if (ret == -EINTR || ret == -EAGAIN) { luring_resubmit(s, luringcb); continue; } -- 2.30.2