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 AE891C433FE for ; Tue, 18 Oct 2022 04:55:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229818AbiJREzL (ORCPT ); Tue, 18 Oct 2022 00:55:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54952 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229845AbiJREzB (ORCPT ); Tue, 18 Oct 2022 00:55:01 -0400 Received: from out30-43.freemail.mail.aliyun.com (out30-43.freemail.mail.aliyun.com [115.124.30.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 461D01C91D; Mon, 17 Oct 2022 21:54:50 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R971e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046050;MF=ziyangzhang@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0VSTAzRM_1666068875; Received: from localhost.localdomain(mailfrom:ZiyangZhang@linux.alibaba.com fp:SMTPD_---0VSTAzRM_1666068875) by smtp.aliyun-inc.com; Tue, 18 Oct 2022 12:54:47 +0800 From: ZiyangZhang To: axboe@kernel.dk, ming.lei@redhat.com Cc: xiaoguang.wang@linux.alibaba.com, linux-block@vger.kernel.org, corbet@lwn.net, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, joseph.qi@linux.alibaba.com, ZiyangZhang Subject: [PATCH 1/1] Documentation: document ublk user recovery feature Date: Tue, 18 Oct 2022 12:53:46 +0800 Message-Id: <20221018045346.99706-2-ZiyangZhang@linux.alibaba.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20221018045346.99706-1-ZiyangZhang@linux.alibaba.com> References: <20221018045346.99706-1-ZiyangZhang@linux.alibaba.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add documentation for user recovery feature of ublk subsystem. Signed-off-by: ZiyangZhang Reviewed-by: Ming Lei --- Documentation/block/ublk.rst | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/Documentation/block/ublk.rst b/Documentation/block/ublk.rst index 2122d1a4a541..ba45c46cc0da 100644 --- a/Documentation/block/ublk.rst +++ b/Documentation/block/ublk.rst @@ -144,6 +144,42 @@ 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_START_USER_RECOVERY`` + + This command is valid if ``UBLK_F_USER_RECOVERY`` feature is enabled. This + command is accepted after the old process has exited, ublk device is quiesced + and ``/dev/ublkc*`` is released. User should send this command before he starts + a new process which re-opens ``/dev/ublkc*``. When this command returns, the + ublk device is ready for the new process. + +- ``UBLK_CMD_END_USER_RECOVERY`` + + This command is valid if ``UBLK_F_USER_RECOVERY`` feature is enabled. This + command is accepted after ublk device is quiesced and a new process has + opened ``/dev/ublkc*`` and get all ublk queues be ready. 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(ublk server's io + handler) is dying, ublk does not delete ``/dev/ublkb*`` during the whole + recovery stage and ublk device ID is kept. It is ublk server's + responsibility to recover the device context by its own knowledge. + Requests which have not been issued to userspace are requeued. Requests + which have been issued to userspace are aborted. + + With ``UBLK_F_USER_RECOVERY_REISSUE`` set, after one ubq_daemon(ublk + server's 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_END_USER_RECOVERY``. + ``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