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envelope-from=vsementsov@virtuozzo.com; helo=EUR02-HE1-obe.outbound.protection.outlook.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/01 06:53:39 X-ACL-Warn: Detected OS = Windows NT kernel [generic] [fuzzy] X-Spam_score_int: -37 X-Spam_score: -3.8 X-Spam_bar: --- X-Spam_report: (-3.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, MSGID_FROM_MTA_HEADER=0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, vsementsov@virtuozzo.com, qemu-devel@nongnu.org, mreitz@redhat.com, stefanha@redhat.com, den@openvz.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Consider nbd_export_close_all(). The call-stack looks like this: nbd_export_close_all() -> nbd_export_close -> call client_close() for each client. client_close() doesn't guarantee that client is closed: nbd_trip() keeps reference to it. So, nbd_export_close_all() just reduce reference counter on export and removes it from the list, but doesn't guarantee that nbd_trip() finished neither export actually removed. Let's wait for all exports actually removed. Without this fix, the following crash is possible: - export bitmap through internal Qemu NBD server - connect a client - shutdown Qemu On shutdown nbd_export_close_all is called, but it actually don't wait for nbd_trip() to finish and to release its references. So, export is not release, and exported bitmap remains busy, and on try to remove the bitmap (which is part of bdrv_close()) the assertion fails: bdrv_release_dirty_bitmap_locked: Assertion `!bdrv_dirty_bitmap_busy(bitmap)' failed Signed-off-by: Vladimir Sementsov-Ogievskiy --- v2: rewritten, try to wait exports directly. Note: I'm not sure in my understanding of AIO_WAIT_WHILE and related things and really hope for review. nbd/server.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/nbd/server.c b/nbd/server.c index 20754e9ebc..9d64b00f4b 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -102,6 +102,8 @@ struct NBDExport { }; static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports); +static QTAILQ_HEAD(, NBDExport) closed_exports = + QTAILQ_HEAD_INITIALIZER(closed_exports); /* NBDExportMetaContexts represents a list of contexts to be exported, * as selected by NBD_OPT_SET_META_CONTEXT. Also used for @@ -1655,6 +1657,7 @@ void nbd_export_close(NBDExport *exp) g_free(exp->name); exp->name = NULL; QTAILQ_REMOVE(&exports, exp, next); + QTAILQ_INSERT_TAIL(&closed_exports, exp, next); } g_free(exp->description); exp->description = NULL; @@ -1717,7 +1720,9 @@ void nbd_export_put(NBDExport *exp) g_free(exp->export_bitmap_context); } + QTAILQ_REMOVE(&closed_exports, exp, next); g_free(exp); + aio_wait_kick(); } } @@ -1737,6 +1742,9 @@ void nbd_export_close_all(void) nbd_export_close(exp); aio_context_release(aio_context); } + + AIO_WAIT_WHILE(NULL, !(QTAILQ_EMPTY(&exports) && + QTAILQ_EMPTY(&closed_exports))); } static int coroutine_fn nbd_co_send_iov(NBDClient *client, struct iovec *iov, -- 2.18.0