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* Mon Dec 08 2025 Jon Maloy <jmaloy@redhat.com> - 10.1.0-8

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- kvm-file-posix-Handle-suspended-dm-multipath-better-for-.patch [RHEL-133303]
- Resolves: RHEL-133303
  (The VM hit io error when do S3-PR integration on the pass-through  failover multipath device [rhel-9])
This commit is contained in:
Jon Maloy 2025-12-08 17:41:34 -05:00
parent 3b087bc2a2
commit 4de7fac8a3
2 changed files with 130 additions and 1 deletions
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122
kvm-file-posix-Handle-suspended-dm-multipath-better-for-.patch Normal file
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@ -0,0 +1,122 @@
From 1005d2951e4b62b07e687d570dfdda6f82461a3f Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Fri, 28 Nov 2025 23:14:40 +0100
Subject: [PATCH] file-posix: Handle suspended dm-multipath better for SG_IO
RH-Author: Kevin Wolf <kwolf@redhat.com>
RH-MergeRequest: 438: file-posix: Handle suspended dm-multipath better for SG_IO
RH-Jira: RHEL-133303
RH-Acked-by: Hanna Czenczek <hreitz@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Commit: [1/1] 575791e00334cf288a89855552967a6eca8c44dd (kmwolf/centos-qemu-kvm)
When introducing DM_MPATH_PROBE_PATHS, we already anticipated that
dm-multipath devices might be suspended for a short time when the DM
tables are reloaded and that they return -EAGAIN in this case. We then
wait for a millisecond and retry.
However, meanwhile it has also turned out that libmpathpersist (which is
used by qemu-pr-helper) may need to perform more complex recovery
operations to get reservations back to expected state if a path failure
happened in the middle of a PR operation. In this case, the device is
suspended for a longer time compared to the case we originally expected.
This patch changes hdev_co_ioctl() to treat -EAGAIN separately so that
it doesn't result in an immediate failure if the device is suspended for
more than 1ms, and moves to incremental backoff to cover both quick and
slow cases without excessive delays.
Buglink: https://issues.redhat.com/browse/RHEL-121543
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20251128221440.89125-1-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 2c3165a1a61c299b4a3ae30899e1cc738d20e004)
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
block/file-posix.c | 56 ++++++++++++++++++++++++++++------------------
1 file changed, 34 insertions(+), 22 deletions(-)
diff --git a/block/file-posix.c b/block/file-posix.c
index 8c738674ce..ace0e23df2 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -4284,25 +4284,8 @@ hdev_open_Mac_error:
static bool coroutine_fn sgio_path_error(int ret, sg_io_hdr_t *io_hdr)
{
if (ret < 0) {
- switch (ret) {
- case -ENODEV:
- return true;
- case -EAGAIN:
- /*
- * The device is probably suspended. This happens while the dm table
- * is reloaded, e.g. because a path is added or removed. This is an
- * operation that should complete within 1ms, so just wait a bit and
- * retry.
- *
- * If the device was suspended for another reason, we'll wait and
- * retry SG_IO_MAX_RETRIES times. This is a tolerable delay before
- * we return an error and potentially stop the VM.
- */
- qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, 1000000);
- return true;
- default:
- return false;
- }
+ /* Path errors sometimes result in -ENODEV */
+ return ret == -ENODEV;
}
if (io_hdr->host_status != SCSI_HOST_OK) {
@@ -4371,6 +4354,7 @@ hdev_co_ioctl(BlockDriverState *bs, unsigned long int req, void *buf)
{
BDRVRawState *s = bs->opaque;
RawPosixAIOData acb;
+ uint64_t eagain_sleep_ns = 1 * SCALE_MS;
int retries = SG_IO_MAX_RETRIES;
int ret;
@@ -4399,9 +4383,37 @@ hdev_co_ioctl(BlockDriverState *bs, unsigned long int req, void *buf)
},
};
- do {
- ret = raw_thread_pool_submit(handle_aiocb_ioctl, &acb);
- } while (req == SG_IO && retries-- && hdev_co_ioctl_sgio_retry(&acb, ret));
+retry:
+ ret = raw_thread_pool_submit(handle_aiocb_ioctl, &acb);
+ if (req == SG_IO && s->use_mpath) {
+ if (ret == -EAGAIN && eagain_sleep_ns < NANOSECONDS_PER_SECOND) {
+ /*
+ * If this is a multipath device, it is probably suspended.
+ *
+ * This can happen while the dm table is reloaded, e.g. because a
+ * path is added or removed. This is an operation that should
+ * complete within 1ms, so just wait a bit and retry.
+ *
+ * There are also some cases in which libmpathpersist must recover
+ * from path failure during its operation, which can leave the
+ * device suspended for a bit longer while the library brings back
+ * reservations into the expected state.
+ *
+ * Use increasing delays to cover both cases without waiting
+ * excessively, and stop after a bit more than a second (1023 ms).
+ * This is a tolerable delay before we return an error and
+ * potentially stop the VM.
+ */
+ qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, eagain_sleep_ns);
+ eagain_sleep_ns *= 2;
+ goto retry;
+ }
+
+ /* Even for ret == 0, the SG_IO header can contain an error */
+ if (retries-- && hdev_co_ioctl_sgio_retry(&acb, ret)) {
+ goto retry;
+ }
+ }
return ret;
}
--
2.51.1

9
qemu-kvm.spec
View File

@ -149,7 +149,7 @@ Obsoletes: %{name}-block-ssh <= %{epoch}:%{version} \
Summary: QEMU is a machine emulator and virtualizer
Name: qemu-kvm
Version: 10.1.0
Release: 7%{?rcrel}%{?dist}%{?cc_suffix}
Release: 8%{?rcrel}%{?dist}%{?cc_suffix}
# Epoch because we pushed a qemu-1.0 package. AIUI this can't ever be dropped
# Epoch 15 used for RHEL 8
# Epoch 17 used for RHEL 9 (due to release versioning offset in RHEL 8.5)
@ -228,6 +228,8 @@ Patch41: kvm-ram-block-attributes-Unify-the-retrieval-of-the-bloc.patch
Patch42: kvm-Fix-the-typo-of-vfio-pci-device-s-enable-migration-o.patch
# For RHEL-133008 - Assertion failure on drain with iothread and I/O load [rhel-9]
Patch43: kvm-block-backend-Fix-race-when-resuming-queued-requests.patch
# For RHEL-133303 - The VM hit io error when do S3-PR integration on the pass-through failover multipath device [rhel-9]
Patch44: kvm-file-posix-Handle-suspended-dm-multipath-better-for-.patch
# For RHEL-11424 - [IBM 9.6 FEAT] KVM: Full boot order support - qemu part
@ -1942,6 +1944,11 @@ useradd -r -u 107 -g qemu -G kvm -d / -s /sbin/nologin \
%endif
%changelog
* Mon Dec 08 2025 Jon Maloy <jmaloy@redhat.com> - 10.1.0-8
- kvm-file-posix-Handle-suspended-dm-multipath-better-for-.patch [RHEL-133303]
- Resolves: RHEL-133303
(The VM hit io error when do S3-PR integration on the pass-through failover multipath device [rhel-9])
* Wed Dec 03 2025 Jon Maloy <jmaloy@redhat.com> - 10.1.0-7
- kvm-block-backend-Fix-race-when-resuming-queued-requests.patch [RHEL-133008]
- Resolves: RHEL-133008