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nbd: take receive_mutex when reading requests[].receiving 

requests[].receiving is set by nbd_receive_replies() under the receive_mutex;
Read it under the same mutex as well.  Waking up receivers on errors happens
after each reply finishes processing, in nbd_co_receive_one_chunk().
If there is no currently-active reply, there are two cases:

* either there is no active request at all, in which case no
element of request[] can have .receiving = true

* or nbd_receive_replies() must be running and owns receive_mutex;
in that case it will get back to nbd_co_receive_one_chunk() because
the socket has been shutdown, and all waiting coroutines will wake up
in turn.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220414175756.671165-9-pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@openvz.org>
Reviewed-by: Lukas Straub <lukasstraub2@web.de>
Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Paolo Bonzini 2022-04-14 19:57:55 +02:00 committed by Eric Blake
parent dba5156c0e
commit a80a9a1c73
1 changed files with 7 additions and 8 deletions
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15
block/nbd.c
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@ -131,6 +131,7 @@ static void nbd_clear_bdrvstate(BlockDriverState *bs)
s->x_dirty_bitmap = NULL;
}
/* Called with s->receive_mutex taken. */
static bool coroutine_fn nbd_recv_coroutine_wake_one(NBDClientRequest *req)
{
if (req->receiving) {
@ -142,12 +143,13 @@ static bool coroutine_fn nbd_recv_coroutine_wake_one(NBDClientRequest *req)
return false;
}
static void coroutine_fn nbd_recv_coroutines_wake(BDRVNBDState *s, bool all)
static void coroutine_fn nbd_recv_coroutines_wake(BDRVNBDState *s)
{
int i;
QEMU_LOCK_GUARD(&s->receive_mutex);
for (i = 0; i < MAX_NBD_REQUESTS; i++) {
if (nbd_recv_coroutine_wake_one(&s->requests[i]) && !all) {
if (nbd_recv_coroutine_wake_one(&s->requests[i])) {
return;
}
}
@ -168,8 +170,6 @@ static void coroutine_fn nbd_channel_error_locked(BDRVNBDState *s, int ret)
} else {
s->state = NBD_CLIENT_QUIT;
}
nbd_recv_coroutines_wake(s, true);
}
static void coroutine_fn nbd_channel_error(BDRVNBDState *s, int ret)
@ -432,11 +432,10 @@ static coroutine_fn int nbd_receive_replies(BDRVNBDState *s, uint64_t handle)
qemu_coroutine_yield();
/*
* We may be woken for 3 reasons:
* We may be woken for 2 reasons:
* 1. From this function, executing in parallel coroutine, when our
* handle is received.
* 2. From nbd_channel_error(), when connection is lost.
* 3. From nbd_co_receive_one_chunk(), when previous request is
* 2. From nbd_co_receive_one_chunk(), when previous request is
* finished and s->reply.handle set to 0.
* Anyway, it's OK to lock the mutex and go to the next iteration.
*/
@ -928,7 +927,7 @@ static coroutine_fn int nbd_co_receive_one_chunk(
}
s->reply.handle = 0;
nbd_recv_coroutines_wake(s, false);
nbd_recv_coroutines_wake(s);
return ret;
}