From patchwork Mon Dec 11 12:06:09 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhao Chen X-Patchwork-Id: 13487108 Received: from out0-221.mail.aliyun.com (out0-221.mail.aliyun.com [140.205.0.221]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E26A5EB for ; Mon, 11 Dec 2023 04:06:13 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R491e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018047204;MF=winters.zc@antgroup.com;NM=1;PH=DS;RN=2;SR=0;TI=SMTPD_---.VhZAIUB_1702296371; Received: from localhost(mailfrom:winters.zc@antgroup.com fp:SMTPD_---.VhZAIUB_1702296371) by smtp.aliyun-inc.com; Mon, 11 Dec 2023 20:06:11 +0800 From: "Zhao Chen" To: linux-fsdevel@vger.kernel.org Cc: miklos@szeredi.hu Subject: [PATCH v3 RESEND 0/2] fuse: Add support for resend pending requests Date: Mon, 11 Dec 2023 20:06:09 +0800 Message-Id: <20231211120611.39543-1-winters.zc@antgroup.com> X-Mailer: git-send-email 2.32.0.3.g01195cf9f Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 After the FUSE daemon crashes, the fuse mount point becomes inaccessible. In some production environments, a watchdog daemon is used to preserve the FUSE connection's file descriptor (fd). When the FUSE daemon crashes, a new FUSE daemon is started and takes over the fd from the watchdog daemon, allowing it to continue providing services. However, if any inflight requests are lost during the crash, the user process becomes stuck as it does not receive any replies. To resolve this issue, this patchset introduces a new notification type that enable resending these pending requests to the FUSE daemon again, allowing the stuck user process to recover. When using the resend API, FUSE daemon needs to ensure avoidance of processing duplicate non-idempotent requests to prevent potential consistency issues. The high bit of the fuse request id is utilized for indicating the resend request. --- v2->v3: - use notification instead of sysfs API to trigger resend - simplify FUSE_REQ_ID_MASK related code - rename some related macro names v1->v2: - remove flush sysfs API in the original mail - add using high bit of request ID for indicating resend requests - add wakeup in fuse_resend_pqueue() Zhao Chen (2): fuse: Introduce a new notification type for resend pending requests fuse: Use the high bit of request ID for indicating resend requests fs/fuse/dev.c | 69 ++++++++++++++++++++++++++++++++++++++- fs/fuse/inode.c | 3 +- include/uapi/linux/fuse.h | 12 +++++++ 3 files changed, 82 insertions(+), 2 deletions(-)