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Fri, 17 Jul 2020 08:55:38 -0400 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-141-gVTc5EiaOy-oG4RMnRGGcw-1; Fri, 17 Jul 2020 08:55:31 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id ED9A28C5A8E; Fri, 17 Jul 2020 12:55:24 +0000 (UTC) Received: from linux.fritz.box.com (ovpn-113-80.ams2.redhat.com [10.36.113.80]) by smtp.corp.redhat.com (Postfix) with ESMTP id 05886710C8; Fri, 17 Jul 2020 12:55:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1594990536; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=176bmdEuvMrg1lCHTVJS3+4pNrYOIDKZBuVZSCBxM1k=; b=FC5smtAYYnOfkzd+/7itGkCGIi7z2hWmE12e5ntqI3NeZto6Q3FzDUHZyt1K9sEuWT69C5 DmXAVWpbVMooPOBgCpTXIfrI0Krmnx119eJPZOTm+gtBrVGnUAvygXNp5fE65F5yb5J15Q iZCzDbgPRkCeykSRlFPpFIU9d2hucU8= X-MC-Unique: gVTc5EiaOy-oG4RMnRGGcw-1 From: Kevin Wolf To: qemu-block@nongnu.org Subject: [PULL 06/12] nbd: make nbd_export_close_all() synchronous Date: Fri, 17 Jul 2020 14:55:04 +0200 Message-Id: <20200717125510.238374-7-kwolf@redhat.com> In-Reply-To: <20200717125510.238374-1-kwolf@redhat.com> References: <20200717125510.238374-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=207.211.31.120; envelope-from=kwolf@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/17 03:33:51 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no 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, peter.maydell@linaro.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) Content-Type: text/plain; charset="utf-8" From: Vladimir Sementsov-Ogievskiy 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 Reviewed-by: Eric Blake Message-Id: <20200714162234.13113-2-vsementsov@virtuozzo.com> Signed-off-by: Kevin Wolf --- nbd/server.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/nbd/server.c b/nbd/server.c index 5357f588f0..4752a6c8bc 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -102,6 +102,8 @@ struct NBDExport { }; =20 static QTAILQ_HEAD(, NBDExport) exports =3D QTAILQ_HEAD_INITIALIZER(export= s); +static QTAILQ_HEAD(, NBDExport) closed_exports =3D + QTAILQ_HEAD_INITIALIZER(closed_exports); =20 /* NBDExportMetaContexts represents a list of contexts to be exported, * as selected by NBD_OPT_SET_META_CONTEXT. Also used for @@ -1659,6 +1661,7 @@ void nbd_export_close(NBDExport *exp) g_free(exp->name); exp->name =3D NULL; QTAILQ_REMOVE(&exports, exp, next); + QTAILQ_INSERT_TAIL(&closed_exports, exp, next); } g_free(exp->description); exp->description =3D NULL; @@ -1722,7 +1725,9 @@ void nbd_export_put(NBDExport *exp) g_free(exp->export_bitmap_context); } =20 + QTAILQ_REMOVE(&closed_exports, exp, next); g_free(exp); + aio_wait_kick(); } } =20 @@ -1742,6 +1747,9 @@ 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))); } =20 static int coroutine_fn nbd_co_send_iov(NBDClient *client, struct iovec *i= ov, --=20 2.25.4