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block/export: Fix vhost-user-blk shutdown with requests in flight

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The vhost-user-blk export runs requests asynchronously in their own
coroutine. When the vhost connection goes away and we want to stop the
vhost-user server, we need to wait for these coroutines to stop before
we can unmap the shared memory. Otherwise, they would still access the
unmapped memory and crash.

This introduces a refcount to VuServer which is increased when spawning
a new request coroutine and decreased before the coroutine exits. The
memory is only unmapped when the refcount reaches zero.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20220125151435.48792-1-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2022-01-25 16:14:35 +01:00
parent c0829cb1fd
commit 520d8b40e8
3 changed files with 32 additions and 0 deletions
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5
block/export/vhost-user-blk-server.c
View File

@ -172,6 +172,7 @@ vu_blk_discard_write_zeroes(VuBlkExport *vexp, struct iovec *iov,
return VIRTIO_BLK_S_IOERR;
}
/* Called with server refcount increased, must decrease before returning */
static void coroutine_fn vu_blk_virtio_process_req(void *opaque)
{
VuBlkReq *req = opaque;
@ -286,10 +287,12 @@ static void coroutine_fn vu_blk_virtio_process_req(void *opaque)
}
vu_blk_req_complete(req);
vhost_user_server_unref(server);
return;
err:
free(req);
vhost_user_server_unref(server);
}
static void vu_blk_process_vq(VuDev *vu_dev, int idx)
@ -310,6 +313,8 @@ static void vu_blk_process_vq(VuDev *vu_dev, int idx)
Coroutine *co =
qemu_coroutine_create(vu_blk_virtio_process_req, req);
vhost_user_server_ref(server);
qemu_coroutine_enter(co);
}
}

5
include/qemu/vhost-user-server.h
View File

@ -42,6 +42,8 @@ typedef struct {
const VuDevIface *vu_iface;
/* Protected by ctx lock */
unsigned int refcount;
bool wait_idle;
VuDev vu_dev;
QIOChannel *ioc; /* The I/O channel with the client */
QIOChannelSocket *sioc; /* The underlying data channel with the client */
@ -59,6 +61,9 @@ bool vhost_user_server_start(VuServer *server,
void vhost_user_server_stop(VuServer *server);
void vhost_user_server_ref(VuServer *server);
void vhost_user_server_unref(VuServer *server);
void vhost_user_server_attach_aio_context(VuServer *server, AioContext *ctx);
void vhost_user_server_detach_aio_context(VuServer *server);

22
util/vhost-user-server.c
View File

@ -74,6 +74,20 @@ static void panic_cb(VuDev *vu_dev, const char *buf)
error_report("vu_panic: %s", buf);
}
void vhost_user_server_ref(VuServer *server)
{
assert(!server->wait_idle);
server->refcount++;
}
void vhost_user_server_unref(VuServer *server)
{
server->refcount--;
if (server->wait_idle && !server->refcount) {
aio_co_wake(server->co_trip);
}
}
static bool coroutine_fn
vu_message_read(VuDev *vu_dev, int conn_fd, VhostUserMsg *vmsg)
{
@ -177,6 +191,14 @@ static coroutine_fn void vu_client_trip(void *opaque)
/* Keep running */
}
if (server->refcount) {
/* Wait for requests to complete before we can unmap the memory */
server->wait_idle = true;
qemu_coroutine_yield();
server->wait_idle = false;
}
assert(server->refcount == 0);
vu_deinit(vu_dev);
/* vu_deinit() should have called remove_watch() */