From bddf389330e11fb0ce17413c1bfa2264a281ded2 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Mon, 30 Mar 2020 11:19:24 +0100 Subject: [PATCH 4/4] mirror: Wait only for in-flight operations RH-Author: Kevin Wolf Message-id: <20200330111924.22938-3-kwolf@redhat.com> Patchwork-id: 94463 O-Subject: [RHEL-AV-8.2.0 qemu-kvm PATCH 2/2] mirror: Wait only for in-flight operations Bugzilla: 1794692 RH-Acked-by: Maxim Levitsky RH-Acked-by: Danilo de Paula RH-Acked-by: Max Reitz mirror_wait_for_free_in_flight_slot() just picks a random operation to wait for. However, a MirrorOp is already in s->ops_in_flight when mirror_co_read() waits for free slots, so if not enough slots are immediately available, an operation can end up waiting for itself, or two or more operations can wait for each other to complete, which results in a hang. Fix this by adding a flag to MirrorOp that tells us if the request is already in flight (and therefore occupies slots that it will later free), and picking only such operations for waiting. Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1794692 Signed-off-by: Kevin Wolf Message-Id: <20200326153628.4869-3-kwolf@redhat.com> Reviewed-by: Eric Blake Signed-off-by: Kevin Wolf (cherry picked from commit ce8cabbd17cf738ddfc68384440c38e5dd2fdf97) Signed-off-by: Kevin Wolf Signed-off-by: Danilo C. L. de Paula --- block/mirror.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/block/mirror.c b/block/mirror.c index 8959e42..5e5a521 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -102,6 +102,7 @@ struct MirrorOp { bool is_pseudo_op; bool is_active_write; + bool is_in_flight; CoQueue waiting_requests; Coroutine *co; @@ -293,7 +294,9 @@ mirror_wait_for_any_operation(MirrorBlockJob *s, bool active) * caller of this function. Since there is only one pseudo op * at any given time, we will always find some real operation * to wait on. */ - if (!op->is_pseudo_op && op->is_active_write == active) { + if (!op->is_pseudo_op && op->is_in_flight && + op->is_active_write == active) + { qemu_co_queue_wait(&op->waiting_requests, NULL); return; } @@ -367,6 +370,7 @@ static void coroutine_fn mirror_co_read(void *opaque) /* Copy the dirty cluster. */ s->in_flight++; s->bytes_in_flight += op->bytes; + op->is_in_flight = true; trace_mirror_one_iteration(s, op->offset, op->bytes); ret = bdrv_co_preadv(s->mirror_top_bs->backing, op->offset, op->bytes, @@ -382,6 +386,7 @@ static void coroutine_fn mirror_co_zero(void *opaque) op->s->in_flight++; op->s->bytes_in_flight += op->bytes; *op->bytes_handled = op->bytes; + op->is_in_flight = true; ret = blk_co_pwrite_zeroes(op->s->target, op->offset, op->bytes, op->s->unmap ? BDRV_REQ_MAY_UNMAP : 0); @@ -396,6 +401,7 @@ static void coroutine_fn mirror_co_discard(void *opaque) op->s->in_flight++; op->s->bytes_in_flight += op->bytes; *op->bytes_handled = op->bytes; + op->is_in_flight = true; ret = blk_co_pdiscard(op->s->target, op->offset, op->bytes); mirror_write_complete(op, ret); @@ -1306,6 +1312,7 @@ static MirrorOp *coroutine_fn active_write_prepare(MirrorBlockJob *s, .offset = offset, .bytes = bytes, .is_active_write = true, + .is_in_flight = true, }; qemu_co_queue_init(&op->waiting_requests); QTAILQ_INSERT_TAIL(&s->ops_in_flight, op, next); -- 1.8.3.1