qemu-kvm/kvm-qed-Don-t-yield-in-bdrv_qed_co_drain_begin.patch

From f628a08d20b9ab6be24c2ab18b38a934a314c78b Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Fri, 18 Nov 2022 18:40:56 +0100
Subject: [PATCH 14/31] qed: Don't yield in bdrv_qed_co_drain_begin()

RH-Author: Stefano Garzarella <sgarzare@redhat.com>
RH-MergeRequest: 135: block: Simplify drain to prevent QEMU from crashing during snapshot
RH-Bugzilla: 2155112
RH-Acked-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
RH-Acked-by: Hanna Czenczek <hreitz@redhat.com>
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Commit: [2/16] f18e9aebb7e04a62e309b656bac8f2ab83df657f (sgarzarella/qemu-kvm-c-9-s)

We want to change .bdrv_co_drained_begin() back to be a non-coroutine
callback, so in preparation, avoid yielding in its implementation.

Because we increase bs->in_flight and bdrv_drained_begin() polls, the
behaviour is unchanged.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20221118174110.55183-2-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 6d47eb0c8bf2d50682c7dccae74d24104076fe23)
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 block/qed.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/block/qed.c b/block/qed.c
index 2f36ad342c..013f826c44 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -282,9 +282,8 @@ static void coroutine_fn qed_unplug_allocating_write_reqs(BDRVQEDState *s)
     qemu_co_mutex_unlock(&s->table_lock);
 }
 
-static void coroutine_fn qed_need_check_timer_entry(void *opaque)
+static void coroutine_fn qed_need_check_timer(BDRVQEDState *s)
 {
-    BDRVQEDState *s = opaque;
     int ret;
 
     trace_qed_need_check_timer_cb(s);
@@ -310,9 +309,20 @@ static void coroutine_fn qed_need_check_timer_entry(void *opaque)
     (void) ret;
 }
 
+static void coroutine_fn qed_need_check_timer_entry(void *opaque)
+{
+    BDRVQEDState *s = opaque;
+
+    qed_need_check_timer(opaque);
+    bdrv_dec_in_flight(s->bs);
+}
+
 static void qed_need_check_timer_cb(void *opaque)
 {
+    BDRVQEDState *s = opaque;
     Coroutine *co = qemu_coroutine_create(qed_need_check_timer_entry, opaque);
+
+    bdrv_inc_in_flight(s->bs);
     qemu_coroutine_enter(co);
 }
 
@@ -363,8 +373,12 @@ static void coroutine_fn bdrv_qed_co_drain_begin(BlockDriverState *bs)
      * header is flushed.
      */
     if (s->need_check_timer && timer_pending(s->need_check_timer)) {
+        Coroutine *co;
+
         qed_cancel_need_check_timer(s);
-        qed_need_check_timer_entry(s);
+        co = qemu_coroutine_create(qed_need_check_timer_entry, s);
+        bdrv_inc_in_flight(bs);
+        aio_co_enter(bdrv_get_aio_context(bs), co);
     }
 }
 
-- 
2.31.1