From ce8cabbd17cf738ddfc68384440c38e5dd2fdf97 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Thu, 26 Mar 2020 16:36:28 +0100 Subject: [PATCH] mirror: Wait only for in-flight operations 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 --- block/mirror.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/block/mirror.c b/block/mirror.c index 5879e63473..c26fd9260d 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); @@ -1319,6 +1325,7 @@ 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); -- 2.30.2