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[PULL 5/6] mirror: Wait only for in-flight operations
From: |
Kevin Wolf |
Subject: |
[PULL 5/6] mirror: Wait only for in-flight operations |
Date: |
Fri, 27 Mar 2020 16:19:49 +0100 |
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 <address@hidden>
Message-Id: <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
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);
--
2.20.1
- [PULL 0/6] Block layer patches, Kevin Wolf, 2020/03/27
- [PULL 1/6] block/iscsi:use the flags in iscsi_open() prevent Clang warning, Kevin Wolf, 2020/03/27
- [PULL 2/6] block: fix bdrv_root_attach_child forget to unref child_bs, Kevin Wolf, 2020/03/27
- [PULL 3/6] nvme: Print 'cqid' for nvme_del_cq, Kevin Wolf, 2020/03/27
- [PULL 4/6] Revert "mirror: Don't let an operation wait for itself", Kevin Wolf, 2020/03/27
- [PULL 6/6] qcow2: Remove unused fields from BDRVQcow2State, Kevin Wolf, 2020/03/27
- [PULL 5/6] mirror: Wait only for in-flight operations,
Kevin Wolf <=
- Re: [PULL 0/6] Block layer patches, Peter Maydell, 2020/03/27