From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794320914; b=5EspThKc1fdC8/lmdrNgWDVsyNUAq5wCF92JK1sR2iH1/6bAVA/plTPnheVNev8sjoeB GgYOo9uuEpRBz2Vts6etxxJheCd7UTuXBbkEnnCEZ3Vmjz32lXaUUIfRoFuU6RhAKDw0z T2AVyL1YQOa/F7OZn+JaqNgj7B569CcO0hBrKnAWVEKaNdoDkjGSQ1ZfDfOWGNtRXrl0X zkoHhlYqhg75qAkKwhBoBk/7TAFTA+bdPrGCeOcMuw9Gu/fBcNWFc/iUdpBuNx/mmC62m +cc5l9B4c7Hvi2eoxCLqzJOdiqutUFcTcwWsKa9X7obajJMhkxEsE0bg4Jq0hm3B6RA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794320914; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=MqraL4pYI3WOLZfdxQ0WEo828k6jsvlr5I93mDDDZtw=; b=JhemThMzn+Ydh9uZWChX+IN3DIdK3oof+o2vDrkj8XULD4IIcWMSr0pAE1yR+pRTWNHd 0nsqukTPMlmIKntzp+ocIO4CWmdVFdv2WmHc4sKwRe4akG2lxoXr3i5Oc7jam0DUM8lji CAgbZr6bo9ftqVtZk75uDaCcHvczZrWTZ+X4FF3uofeARdfc8KC/wlnJLO4/pH+4dvioA eboRisRIHfG0OhO2PjgoQkYQaEc8b/iC890LfDFbExbbN2OUKQwv7FEAqePNuS2WfIfeW IIzUeHD+vwT5cxqMa3rRaFQGo4wUQFAggM/ONdg4bLIgxuERYccpFb0gFytNbuIrLdw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=af9z43iA; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ED14560727EC for ; Tue, 10 Nov 2026 14:28:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=af9z43iA Received: by smtp.kernel.org (Postfix) with ESMTPSA id E89A21F008AB; Tue, 10 Nov 2026 14:28:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794320913; bh=MqraL4pYI3WOLZfdxQ0WEo828k6jsvlr5I93mDDDZtw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=af9z43iAMUfFYd3blh/i3lSx+H5ZhDPUPAaDRtT2K8Kj3IrM8B80A1pxbuYGO+WmS qw4I3fk43Ni6Mbr8JrtMwJuFmk78usTsdq0F1m8H6QZHX4j/RkexnirF+yjVTme1++ MPTy1tEJ/z4UP2tXnFeFUO4K6rdfYzy4+YHMZSPUq8JFzPVVQ5N5FSPH9+Tz6eutmn d1fY8b9HpzHczCj5MEVsKZMYa75KN0FYMhU4Njq6C1jaEEuZqWPJPkSof4hnB/xGkF pPmTeSaBRNAcd3GktsllNbeMetfZQDsz/yF5y//TC6PKJthooPB+k43XXUxQXvT0om FqCAak97yrUAw== From: Sasha Levin To: stable@vger.kernel.org Cc: Ming Lei , Josef Bacik , Jens Axboe , Sasha Levin Subject: [PATCH 6.18.y] ublk: keep a canceled FETCH round canceling until the server is gone Date: Tue, 10 Nov 2026 09:28:31 -0500 Message-ID: <20261110142814.1876003-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261107051205-failed-6.18-4c454b5b2634@kernel.org> References: <20261107051205-failed-6.18-4c454b5b2634@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Ming Lei [ Upstream commit 4c454b5b2634d982caf797fbe477770c3edfc983 ] A cancel completes a fetched io command and sets io->cmd to NULL, but the io still counts as ready. Only ubq->canceling stops ublk_queue_rq() from using the NULL io->cmd. Two paths clear that flag too early: partial FETCH round recovery, two queues ------------------- -------------------- task A: FETCH tags 0-2 q0 ready: q0->canceling = false task A exits: q0 task exits: start_cancel(): mark queues start_cancel(): ub->canceling tags 0-2: io->cmd = NULL is still set -> q0 not marked task B: FETCH tag 3 q0: io->cmd = NULL queue ready: canceling = false q1 ready START_DEV END_USER_RECOVERY read -> ublk_queue_cmd(NULL) read on q0 -> ublk_queue_cmd(NULL) A FETCH round runs from the open of /dev/ublkcN until ublk_reset_ch_dev() resets the queues. A canceled command can't be fetched again in the same round. So the ready check only needs one fact: did this round see a cancel? ub->canceling already records it: ublk_start_cancel() sets it under cancel_mutex before any command is taken. It is only cleared too early, when all queues are ready. Fix: - clear ub->canceling only in ublk_reset_ch_dev() - when a queue gets ready, clear ubq->canceling only if ub->canceling is not set, and check it under cancel_mutex The check and the marking are ordered by cancel_mutex: check first: queue cleared -> start_cancel() marks it again -> command taken cancel first: check sees ub->canceling -> queue stays canceling While ub->canceling is set, no queue clears its flag. So the "all queues marked" shortcut in ublk_start_cancel() is correct again. UBLK_F_BATCH_IO follows the same rule. It does not dispatch through io->cmd, so it never hit the oops, but a round which lost a fetch command is treated the same way: it has to start over. Fixes: 728cbac5fe21 ("ublk: move device reset into ublk_ch_release()") Fixes: 3f3850785594 ("ublk: fix batch I/O recovery -ENODEV error") Cc: stable@vger.kernel.org # v6.17+: needs cancel_mutex Reported-by: Josef Bacik Closes: https://lore.kernel.org/linux-block/20260928-b4-ublk-cancel-stop-v1-0-4a4360232a46@toxicpanda.com/ Tested-by: Josef Bacik Signed-off-by: Ming Lei Link: https://patch.msgid.link/20261011063555.1142277-2-tom.leiming@gmail.com Signed-off-by: Jens Axboe [ sashal: Adapted per-queue readiness handling to the existing device-wide ublk_reset_io_flags() helper. ] Signed-off-by: Sasha Levin --- drivers/block/ublk_drv.c | 31 ++++++++++++++++++++++++------- 1 file changed, 24 insertions(+), 7 deletions(-) diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c index 6b2035c46daa3..c0e4f94cc43b0 100644 --- a/drivers/block/ublk_drv.c +++ b/drivers/block/ublk_drv.c @@ -233,6 +233,11 @@ struct ublk_device { u32 nr_io_ready; bool unprivileged_daemons; struct mutex cancel_mutex; + /* + * A cancel started in this FETCH round. Set by ublk_set_canceling(), + * cleared only by ublk_reset_ch_dev() when a new round starts. While + * it is set, no queue clears its ->canceling. + */ bool canceling; pid_t ublksrv_tgid; struct delayed_work exit_work; @@ -1637,6 +1642,11 @@ static void ublk_reset_ch_dev(struct ublk_device *ub) for (i = 0; i < ub->dev_info.nr_hw_queues; i++) ublk_queue_reinit(ub, ublk_get_queue(ub, i)); + /* a new FETCH round starts, the queues stay canceling until ready */ + mutex_lock(&ub->cancel_mutex); + ub->canceling = false; + mutex_unlock(&ub->cancel_mutex); + /* set to NULL, otherwise new tasks cannot mmap io_cmd_buf */ ub->mm = NULL; ub->nr_io_ready = 0; @@ -2152,8 +2162,15 @@ static void ublk_reset_io_flags(struct ublk_device *ub) for (i = 0; i < ub->dev_info.nr_hw_queues; i++) ublk_get_queue(ub, i)->fail_io = false; + /* + * A cancel in this FETCH round took a command which still counts as + * ready, so the queues have to stay canceling. ub->canceling is set + * under cancel_mutex before any command is taken: either we see it + * here, or the cancel marks these queues again later. + */ mutex_lock(&ub->cancel_mutex); - ublk_set_canceling(ub, false); + if (!ub->canceling) + ublk_set_canceling(ub, false); mutex_unlock(&ub->cancel_mutex); } @@ -2173,9 +2190,8 @@ static void ublk_mark_io_ready(struct ublk_device *ub, struct ublk_queue *ubq, ub->nr_io_ready++; if (ublk_dev_ready(ub)) { /* - * now we are ready for handling ublk io request, clear - * device-level canceling flag and wake ublk_dev_ready() - * waiters + * Reset queue flags unless this round saw a cancel, and + * wake ublk_dev_ready() waiters. */ ublk_reset_io_flags(ub); wake_up_var(&ub->nr_io_ready); @@ -2996,9 +3012,10 @@ static bool ublk_validate_user_pid(struct ublk_device *ub, pid_t ublksrv_pid) /* * Wait until all queues have fetched their I/O commands, and return with - * ub->mutex held and readiness guaranteed: then every queue's ->canceling - * is cleared. Ready may regress between wakeup and mutex_lock() (daemon - * death), so re-check it under the mutex and wait again. + * ub->mutex held and readiness guaranteed. The queues stay canceling if + * this round saw a cancel, see ublk_reset_io_flags(). Ready may regress + * between wakeup and mutex_lock() (daemon death), so re-check it under + * the mutex and wait again. */ static int ublk_wait_dev_ready_and_lock(struct ublk_device *ub) { -- 2.53.0