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block/io: split out bdrv_find_conflicting_request

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To be reused in separate.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20201021145859.11201-4-vsementsov@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2020-10-21 17:58:41 +03:00 committed by Max Reitz
parent 2e36da62cf
commit 3183937ff9
1 changed files with 40 additions and 29 deletions
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69
block/io.c
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@ -754,43 +754,54 @@ static bool tracked_request_overlaps(BdrvTrackedRequest *req,
return true;
}
/* Called with self->bs->reqs_lock held */
static BdrvTrackedRequest *
bdrv_find_conflicting_request(BdrvTrackedRequest *self)
{
BdrvTrackedRequest *req;
QLIST_FOREACH(req, &self->bs->tracked_requests, list) {
if (req == self || (!req->serialising && !self->serialising)) {
continue;
}
if (tracked_request_overlaps(req, self->overlap_offset,
self->overlap_bytes))
{
/*
* Hitting this means there was a reentrant request, for
* example, a block driver issuing nested requests. This must
* never happen since it means deadlock.
*/
assert(qemu_coroutine_self() != req->co);
/*
* If the request is already (indirectly) waiting for us, or
* will wait for us as soon as it wakes up, then just go on
* (instead of producing a deadlock in the former case).
*/
if (!req->waiting_for) {
return req;
}
}
}
return NULL;
}
static bool coroutine_fn
bdrv_wait_serialising_requests_locked(BlockDriverState *bs,
BdrvTrackedRequest *self)
{
BdrvTrackedRequest *req;
bool retry;
bool waited = false;
do {
retry = false;
QLIST_FOREACH(req, &bs->tracked_requests, list) {
if (req == self || (!req->serialising && !self->serialising)) {
continue;
}
if (tracked_request_overlaps(req, self->overlap_offset,
self->overlap_bytes))
{
/* Hitting this means there was a reentrant request, for
* example, a block driver issuing nested requests. This must
* never happen since it means deadlock.
*/
assert(qemu_coroutine_self() != req->co);
while ((req = bdrv_find_conflicting_request(self))) {
self->waiting_for = req;
qemu_co_queue_wait(&req->wait_queue, &bs->reqs_lock);
self->waiting_for = NULL;
waited = true;
}
/* If the request is already (indirectly) waiting for us, or
* will wait for us as soon as it wakes up, then just go on
* (instead of producing a deadlock in the former case). */
if (!req->waiting_for) {
self->waiting_for = req;
qemu_co_queue_wait(&req->wait_queue, &bs->reqs_lock);
self->waiting_for = NULL;
retry = true;
waited = true;
break;
}
}
}
} while (retry);
return waited;
}