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io_uring: resubmit when result is -EAGAIN

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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>
This commit is contained in:
Fabian Ebner 2021-07-29 11:50:31 +02:00 committed by Thomas Lamprecht
parent bb3e494bdc
commit 0114d3cd02
2 changed files with 50 additions and 0 deletions
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49
debian/patches/extra/0002-block-io_uring-resubmit-when-result-is-EAGAIN.patch vendored Normal file
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@ -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

1
debian/patches/series vendored
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@ -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