From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 795F9C32771 for ; Wed, 21 Sep 2022 10:01:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231641AbiIUKBy (ORCPT ); Wed, 21 Sep 2022 06:01:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50706 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231477AbiIUKBV (ORCPT ); Wed, 21 Sep 2022 06:01:21 -0400 Received: from out30-45.freemail.mail.aliyun.com (out30-45.freemail.mail.aliyun.com [115.124.30.45]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C21918B2E3; Wed, 21 Sep 2022 03:01:05 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R211e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045168;MF=ziyangzhang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VQNuDpk_1663754457; Received: from localhost.localdomain(mailfrom:ZiyangZhang@linux.alibaba.com fp:SMTPD_---0VQNuDpk_1663754457) by smtp.aliyun-inc.com; Wed, 21 Sep 2022 18:01:03 +0800 From: ZiyangZhang To: ming.lei@redhat.com Cc: axboe@kernel.dk, xiaoguang.wang@linux.alibaba.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, joseph.qi@linux.alibaba.com, ZiyangZhang Subject: [PATCH V4 8/8] Documentation: document ublk user recovery feature Date: Wed, 21 Sep 2022 17:58:49 +0800 Message-Id: <20220921095849.84988-9-ZiyangZhang@linux.alibaba.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20220921095849.84988-1-ZiyangZhang@linux.alibaba.com> References: <20220921095849.84988-1-ZiyangZhang@linux.alibaba.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Add documentation for user recovery feature of ublk subsystem. Signed-off-by: ZiyangZhang --- Documentation/block/ublk.rst | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/Documentation/block/ublk.rst b/Documentation/block/ublk.rst index 2122d1a4a541..3f1bfd51898b 100644 --- a/Documentation/block/ublk.rst +++ b/Documentation/block/ublk.rst @@ -144,6 +144,31 @@ managing and controlling ublk devices with help of several control commands: For retrieving device info via ``ublksrv_ctrl_dev_info``. It is the server's responsibility to save IO target specific info in userspace. +- ``UBLK_CMD_RESTART_DEV`` + + This command is valid if ``UBLK_F_USER_RECOVERY`` feature is enabled. The old + process has exited and ublk device is quiesced. Then, user should start a new + process which opens ``/dev/ublkc*`` and gets all ublk queues be ready. Finally + user should send this command. When this command returns, ublk device is + unquiesced and new I/O requests are passed to the new process. + +- user recovery feature description + + Two new features are added for user recovery: ``UBLK_F_USER_RECOVERY`` and + ``UBLK_F_USER_RECOVERY_REISSUE``. + + With ``UBLK_F_USER_RECOVERY`` set, after one ubq_daemon(ublksrv io handler) is + dying, ublk does not release ``/dev/ublkc*`` or ``/dev/ublkb*`` but requeues all + inflight requests which have not been issued to userspace. Requests which have + been issued to userspace are aborted. + + With ``UBLK_F_USER_RECOVERY_REISSUE`` set, after one ubq_daemon(ublksrv io + handler) is dying, contrary to ``UBLK_F_USER_RECOVERY``, requests which have been + issued to userspace are requeued and will be re-issued to the new process after + handling ``UBLK_CMD_RESTART_DEV``. ``UBLK_F_USER_RECOVERY_REISSUE`` is designed + for backends who tolerate double-write since the driver may issue the same + I/O request twice. It might be useful to a read-only FS or a VM backend. + Data plane ---------- -- 2.27.0