From mboxrd@z Thu Jan 1 00:00:00 1970
Return-Path: <f.ebner@proxmox.com>
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) server-digest SHA256)
(No client certificate requested)
by lists.proxmox.com (Postfix) with ESMTPS id 5EF5969ED1
for <pve-devel@lists.proxmox.com>; Thu, 29 Jul 2021 11:51:12 +0200 (CEST)
Received: from firstgate.proxmox.com (localhost [127.0.0.1])
by firstgate.proxmox.com (Proxmox) with ESMTP id 3019D2D6C0
for <pve-devel@lists.proxmox.com>; Thu, 29 Jul 2021 11:50:42 +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) server-digest SHA256)
(No client certificate requested)
by firstgate.proxmox.com (Proxmox) with ESMTPS id A74EA2D6B4
for <pve-devel@lists.proxmox.com>; Thu, 29 Jul 2021 11:50:39 +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 69E3242C38
for <pve-devel@lists.proxmox.com>; Thu, 29 Jul 2021 11:50:39 +0200 (CEST)
From: Fabian Ebner <f.ebner@proxmox.com>
To: pve-devel@lists.proxmox.com
Date: Thu, 29 Jul 2021 11:50:31 +0200
Message-Id: <20210729095031.90694-1-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 0.467 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
Subject: [pve-devel] [PATCH v2 qemu] 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 <pve-devel.lists.proxmox.com>
List-Unsubscribe: <https://lists.proxmox.com/cgi-bin/mailman/options/pve-devel>,
<mailto:pve-devel-request@lists.proxmox.com?subject=unsubscribe>
List-Archive: <http://lists.proxmox.com/pipermail/pve-devel/>
List-Post: <mailto:pve-devel@lists.proxmox.com>
List-Help: <mailto:pve-devel-request@lists.proxmox.com?subject=help>
List-Subscribe: <https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel>,
<mailto:pve-devel-request@lists.proxmox.com?subject=subscribe>
X-List-Received-Date: Thu, 29 Jul 2021 09:51:12 -0000
Linux SCSI can throw spurious -EAGAIN in some corner cases in its
completion path, which will end up being the result in the completed
io_uring request.
Resubmitting such requests should allow block jobs to complete, even
if such spurious errors are encountered.
Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>
---
Changes from v1:
* make it a patch for pve-qemu instead of the qemu submodule
* use v2 of the patch with a comment by Stefan Hajnoczi
...uring-resubmit-when-result-is-EAGAIN.patch | 49 +++++++++++++++++++
debian/patches/series | 1 +
2 files changed, 50 insertions(+)
create mode 100644 debian/patches/extra/0002-block-io_uring-resubmit-when-result-is-EAGAIN.patch
diff --git a/debian/patches/extra/0002-block-io_uring-resubmit-when-result-is-EAGAIN.patch b/debian/patches/extra/0002-block-io_uring-resubmit-when-result-is-EAGAIN.patch
new file mode 100644
index 0000000..b5dd07a
--- /dev/null
+++ b/debian/patches/extra/0002-block-io_uring-resubmit-when-result-is-EAGAIN.patch
@@ -0,0 +1,49 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Fabian Ebner <f.ebner@proxmox.com>
+Date: Fri, 23 Jul 2021 12:42:23 +0200
+Subject: [PATCH] block/io_uring: resubmit when result is -EAGAIN
+
+Linux SCSI can throw spurious -EAGAIN in some corner cases in its
+completion path, which will end up being the result in the completed
+io_uring request.
+
+Resubmitting such requests should allow block jobs to complete, even
+if such spurious errors are encountered.
+
+Co-authored-by: Stefan Hajnoczi <stefanha@gmail.com>
+Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
+Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>
+---
+ block/io_uring.c | 16 +++++++++++++++-
+ 1 file changed, 15 insertions(+), 1 deletion(-)
+
+diff --git a/block/io_uring.c b/block/io_uring.c
+index 00a3ee9fb8..dfa475cc87 100644
+--- a/block/io_uring.c
++++ b/block/io_uring.c
+@@ -165,7 +165,21 @@ static void luring_process_completions(LuringState *s)
+ total_bytes = ret + luringcb->total_read;
+
+ if (ret < 0) {
+- if (ret == -EINTR) {
++ /*
++ * Only writev/readv/fsync requests on regular files or host block
++ * devices are submitted. Therefore -EAGAIN is not expected but it's
++ * known to happen sometimes with Linux SCSI. Submit again and hope
++ * the request completes successfully.
++ *
++ * For more information, see:
++ * https://lore.kernel.org/io-uring/20210727165811.284510-3-axboe@kernel.dk/T/#u
++ *
++ * If the code is changed to submit other types of requests in the
++ * future, then this workaround may need to be extended to deal with
++ * genuine -EAGAIN results that should not be resubmitted
++ * immediately.
++ */
++ if (ret == -EINTR || ret == -EAGAIN) {
+ luring_resubmit(s, luringcb);
+ continue;
+ }
+--
+2.30.2
+
diff --git a/debian/patches/series b/debian/patches/series
index ada674b..6edf8ce 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -1,4 +1,5 @@
extra/0001-monitor-qmp-fix-race-on-CHR_EVENT_CLOSED-without-OOB.patch
+extra/0002-block-io_uring-resubmit-when-result-is-EAGAIN.patch
bitmap-mirror/0001-drive-mirror-add-support-for-sync-bitmap-mode-never.patch
bitmap-mirror/0002-drive-mirror-add-support-for-conditional-and-always-.patch
bitmap-mirror/0003-mirror-add-check-for-bitmap-mode-without-bitmap.patch
--
2.30.2