From patchwork Mon Dec 26 10:33:08 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hou Tao X-Patchwork-Id: 36589 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:4e01:0:0:0:0:0 with SMTP id p1csp849627wrt; Mon, 26 Dec 2022 02:57:14 -0800 (PST) X-Google-Smtp-Source: AMrXdXvlcvLdcFonzEo5DcKu7eC9AgKl1mkR8S3kxL6ZPd14/OT5gfrqMSSSdzGNaRMCzNNvXUXR X-Received: by 2002:a17:907:9d03:b0:7c1:a0c:a866 with SMTP id kt3-20020a1709079d0300b007c10a0ca866mr15616810ejc.75.1672052234435; Mon, 26 Dec 2022 02:57:14 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1672052234; cv=none; d=google.com; s=arc-20160816; b=XDphOyUdg9DRtTbZIbnOlqkXvlMWeR2qy7HMglWQAIFuYL4ZxxmSXplD0d2cIrhw9p WtpeR76O+UdxCXRewnF233tJcelW7J/zi1dJ+YdpsIhnJ5ZHRZSaG92bhwc+SUWoLPDM SPAMmTPOH6mtNXkvU3XY+GXA6H4FBkn4pxv24JCLPkNRALxVuwgGfQY8F8ZHaFTc8FPp soqToO6CobaENaDrpgAvU88IeM0dNPnUunM+grPGcVYQWXK6xpv84XIkJUXcbWijJtbc 9cqNiMt6JwjB/e4VUwXriWjQ9C5R4n2HlmjYDACTUf0dBB9truTynPLzARUfNkKfcfxH 9BIQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from; bh=/Phdeb4YIDP8cG7b5A0ptqX7HDgtNj3DsW/jw3l03iM=; b=xU4WQMo4comBikSGJj6S6b2MACIfqFYQQB8QTRAICmHCKJIuL2TbR/+Zg/ZN8wU3sD arHcDMynesRU2x6DGt69vFnHkrZchZ/1IjIrwvqLlIAtDDF4C1POEjjv5QtwCkW8GKAW uvoXzhQIHhQw3UrSpgMn961ha8Pc9KsiITcfwyhE4M18ApcKscFCfH6isH8W7irzH+7D 0nH9cU/BqcTZ79dzHQwY11nN8Gvr14bFvfbMJmjw1KEla2iR5jOEgAYtKiYwBkjUZ1a8 SGjMYp3ebRkvdmoRo8SAJ0Hll+ZjoOnjo7QlB/flLl3uUWezSfmRFMWltrKO5CAce7qF sgnA== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id ae2-20020a17090725c200b007c103219025si7597619ejc.825.2022.12.26.02.56.50; Mon, 26 Dec 2022 02:57:14 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231889AbiLZKda (ORCPT + 99 others); Mon, 26 Dec 2022 05:33:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46766 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229484AbiLZKdX (ORCPT ); Mon, 26 Dec 2022 05:33:23 -0500 Received: from dggsgout12.his.huawei.com (dggsgout12.his.huawei.com [45.249.212.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B34CF6160 for ; Mon, 26 Dec 2022 02:33:21 -0800 (PST) Received: from mail02.huawei.com (unknown [172.30.67.153]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4NgYyz6skQz4f3l1t for ; Mon, 26 Dec 2022 18:33:15 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.124.27]) by APP4 (Coremail) with SMTP id gCh0CgBH_rFreKlj6SMxAg--.54373S5; Mon, 26 Dec 2022 18:33:18 +0800 (CST) From: Hou Tao To: linux-cachefs@redhat.com Cc: David Howells , Jeff Layton , linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org, Jingbo Xu , houtao1@huawei.com Subject: [PATCH v2 1/2] fscache: Use wait_on_bit() to wait for the freeing of relinquished volume Date: Mon, 26 Dec 2022 18:33:08 +0800 Message-Id: <20221226103309.953112-2-houtao@huaweicloud.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20221226103309.953112-1-houtao@huaweicloud.com> References: <20221226103309.953112-1-houtao@huaweicloud.com> MIME-Version: 1.0 X-CM-TRANSID: gCh0CgBH_rFreKlj6SMxAg--.54373S5 X-Coremail-Antispam: 1UD129KBjvJXoWxCF45KrWftrWxXrWxury7trb_yoW5KFWkp3 9I9343trW8X3sFyw4kJw47Z34SgFykJan7CrWvkry7Aa1rtF15tF10k3s8uay7A3yDJrW2 va1jq3sIgw1UAFJanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvGb4IE77IF4wAFF20E14v26ryj6rWUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28IrcIa0xkI8VA2jI8067AKxVWUGw A2048vs2IY020Ec7CjxVAFwI0_JFI_Gr1l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxS w2x7M28EF7xvwVC0I7IYx2IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxV W8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E14v2 6rxl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMc Ij6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_ Jr0_Gr1lF7xvr2IYc2Ij64vIr41l42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr 0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY 17CE14v26r126r1DMIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcV C0I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY 6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWIevJa 73UjIFyTuYvjxUzl1vUUUUU X-CM-SenderInfo: xkrx3t3r6k3tpzhluzxrxghudrp/ X-CFilter-Loop: Reflected X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1753273843989784537?= X-GMAIL-MSGID: =?utf-8?q?1753273843989784537?= From: Hou Tao The freeing of relinquished volume will wake up the pending volume acquisition by using wake_up_bit(), however it is mismatched with wait_var_event() used in fscache_wait_on_volume_collision() and it will never wake up the waiter in the wait-queue because these two functions operate on different wait-queues. According to the implementation in fscache_wait_on_volume_collision(), if the wake-up of pending acquisition is delayed longer than 20 seconds (e.g., due to the delay of on-demand fd closing), the first wait_var_event_timeout() will timeout and the following wait_var_event() will hang forever as shown below: FS-Cache: Potential volume collision new=00000024 old=00000022 ...... INFO: task mount:1148 blocked for more than 122 seconds. Not tainted 6.1.0-rc6+ #1 task:mount state:D stack:0 pid:1148 ppid:1 Call Trace: __schedule+0x2f6/0xb80 schedule+0x67/0xe0 fscache_wait_on_volume_collision.cold+0x80/0x82 __fscache_acquire_volume+0x40d/0x4e0 erofs_fscache_register_volume+0x51/0xe0 [erofs] erofs_fscache_register_fs+0x19c/0x240 [erofs] erofs_fc_fill_super+0x746/0xaf0 [erofs] vfs_get_super+0x7d/0x100 get_tree_nodev+0x16/0x20 erofs_fc_get_tree+0x20/0x30 [erofs] vfs_get_tree+0x24/0xb0 path_mount+0x2fa/0xa90 do_mount+0x7c/0xa0 __x64_sys_mount+0x8b/0xe0 do_syscall_64+0x30/0x60 entry_SYSCALL_64_after_hwframe+0x46/0xb0 Considering that wake_up_bit() is more selective, so fixing it by using wait_on_bit() instead of wait_var_event() to wait for the freeing of relinquished volume. In addition because waitqueue_active() is used in wake_up_bit() and clear_bit() doesn't imply any memory barrier, so also adding smp_mb__after_atomic() before wake_up_bit(). Fixes: 62ab63352350 ("fscache: Implement volume registration") Signed-off-by: Hou Tao Reviewed-by: Jingbo Xu --- fs/fscache/volume.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/fs/fscache/volume.c b/fs/fscache/volume.c index ab8ceddf9efa..fc3dd3bc851d 100644 --- a/fs/fscache/volume.c +++ b/fs/fscache/volume.c @@ -141,13 +141,14 @@ static bool fscache_is_acquire_pending(struct fscache_volume *volume) static void fscache_wait_on_volume_collision(struct fscache_volume *candidate, unsigned int collidee_debug_id) { - wait_var_event_timeout(&candidate->flags, - !fscache_is_acquire_pending(candidate), 20 * HZ); + wait_on_bit_timeout(&candidate->flags, FSCACHE_VOLUME_ACQUIRE_PENDING, + TASK_UNINTERRUPTIBLE, 20 * HZ); if (fscache_is_acquire_pending(candidate)) { pr_notice("Potential volume collision new=%08x old=%08x", candidate->debug_id, collidee_debug_id); fscache_stat(&fscache_n_volumes_collision); - wait_var_event(&candidate->flags, !fscache_is_acquire_pending(candidate)); + wait_on_bit(&candidate->flags, FSCACHE_VOLUME_ACQUIRE_PENDING, + TASK_UNINTERRUPTIBLE); } } @@ -348,6 +349,11 @@ static void fscache_wake_pending_volume(struct fscache_volume *volume, if (fscache_volume_same(cursor, volume)) { fscache_see_volume(cursor, fscache_volume_see_hash_wake); clear_bit(FSCACHE_VOLUME_ACQUIRE_PENDING, &cursor->flags); + /* + * Paired with barrier in wait_on_bit(). Check + * wake_up_bit() and waitqueue_active() for details. + */ + smp_mb__after_atomic(); wake_up_bit(&cursor->flags, FSCACHE_VOLUME_ACQUIRE_PENDING); return; } From patchwork Mon Dec 26 10:33:09 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hou Tao X-Patchwork-Id: 36588 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:4e01:0:0:0:0:0 with SMTP id p1csp848811wrt; Mon, 26 Dec 2022 02:54:16 -0800 (PST) X-Google-Smtp-Source: AMrXdXtKT1LWfwxw9n86q74WhjwvjN+XAwEF7g7l+Ta79H5NYy3shjPlkWhQJFx83n8x0IAJ1pD+ X-Received: by 2002:a17:907:a803:b0:7c3:15cc:76d0 with SMTP id vo3-20020a170907a80300b007c315cc76d0mr18411373ejc.47.1672052056185; Mon, 26 Dec 2022 02:54:16 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1672052056; cv=none; d=google.com; s=arc-20160816; b=dRbTA5RgoLQf+XiGHc7ucic/bEnf/b0nkaPiFJQG6DpoCz2ceTJtqqUz39zIk9atEo aANwYpxLV1+hiZAtWl9wjZIgXeNu3pMB8NWflGBZe56XNdALGrGOflKGuaJtG/wh5pB6 MCGg7EezS83ARDhsGPe2sAZiUssEbu001HpaVJlM2x5VRegBEhVYy/o7kMV21U/Qr/OM cIxURZ1a0n61vCntOCv836l4VQ36Nez7qwyTdnJJzmDveKHtaMn5vhOr1IWxLZKK0pwf Ipb6+aDAqr+lklarSQcmGuTidUuT9cAsuu2SZaFZey0YODL9Ev15mfJciXdANkEerUga Gh+w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from; bh=/8iJERifRuDgkKMvQvGyxuwsw9IX1lKSaIBEuKbKFZc=; b=r7W5QmoxiMrY30h+ehoEtT+buRXm6gf1GEUgRIJB676ZMzZCxhNEtmQWB1j9vSPoo1 YvRT56Bw2y4rQfMapOdcBhZsebzKyAY+KHTb/Gpovy+vaGp614WLpUvf/sUZJS3qeACa SWy0jYIT2GxoH/1+c304jXiI9/qpaIR2l3KzflmkH2Nvl9n9QiBucmymI2iwnJLTWPPE h4z0CYnCoDWlP7f3iJ36g47mt+vQdRrT62FfAmL7cu0hO5s4vwNSl/Yzumgp01FrCbSd DswAxwlGB5YnvNPoC1J9+92TPYtaZ20lK7AGwf6VEofd63KN5ssJC90R0tQwpn/3foM0 ig0w== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id g23-20020a170906349700b007316843d58bsi6681318ejb.925.2022.12.26.02.53.49; Mon, 26 Dec 2022 02:54:16 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231873AbiLZKd0 (ORCPT + 99 others); Mon, 26 Dec 2022 05:33:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46768 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229450AbiLZKdX (ORCPT ); Mon, 26 Dec 2022 05:33:23 -0500 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B35586161 for ; Mon, 26 Dec 2022 02:33:21 -0800 (PST) Received: from mail02.huawei.com (unknown [172.30.67.153]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4NgYz03ZqSz4f3p0c for ; Mon, 26 Dec 2022 18:33:16 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.124.27]) by APP4 (Coremail) with SMTP id gCh0CgBH_rFreKlj6SMxAg--.54373S6; Mon, 26 Dec 2022 18:33:19 +0800 (CST) From: Hou Tao To: linux-cachefs@redhat.com Cc: David Howells , Jeff Layton , linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org, Jingbo Xu , houtao1@huawei.com Subject: [PATCH v2 2/2] fscache: Add the missing smp_mb__after_atomic() before wake_up_bit() Date: Mon, 26 Dec 2022 18:33:09 +0800 Message-Id: <20221226103309.953112-3-houtao@huaweicloud.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20221226103309.953112-1-houtao@huaweicloud.com> References: <20221226103309.953112-1-houtao@huaweicloud.com> MIME-Version: 1.0 X-CM-TRANSID: gCh0CgBH_rFreKlj6SMxAg--.54373S6 X-Coremail-Antispam: 1UD129KBjvJXoW7tryxXF18tr4DCF48ZF47Arb_yoW8Gr18pr Z5WFySqay8X39rt3yDJw17u34SgrWUKanrGr10y3WUZF4FqrWFv3WSkas8u3W7C398Xry3 ZF15K3y3XF1UZr7anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvGb4IE77IF4wAFF20E14v26rWj6s0DM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28IrcIa0xkI8VA2jI8067AKxVWUXw A2048vs2IY020Ec7CjxVAFwI0_Gr0_Xr1l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxS w2x7M28EF7xvwVC0I7IYx2IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxV W8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E14v2 6rxl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMc Ij6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_ Jr0_Gr1lF7xvr2IYc2Ij64vIr41l42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr 0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY 17CE14v26r126r1DMIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcV C0I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY 6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWIevJa 73UjIFyTuYvjxU2GYLDUUUU X-CM-SenderInfo: xkrx3t3r6k3tpzhluzxrxghudrp/ X-CFilter-Loop: Reflected X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1753273656786916432?= X-GMAIL-MSGID: =?utf-8?q?1753273656786916432?= From: Hou Tao fscache_create_volume_work() uses wake_up_bit() to wake up the processes which are waiting for the completion of volume creation. According to comments in wake_up_bit() and waitqueue_active(), an extra smp_mb() is needed to guarantee the memory order between FSCACHE_VOLUME_CREATING flag and waitqueue_active() before invoking wake_up_bit(). Considering clear_bit_unlock() before wake_up_bit() is an atomic operation, use smp_mb__after_atomic() instead of smp_mb() to provide such guarantee. Signed-off-by: Hou Tao --- fs/fscache/volume.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/fscache/volume.c b/fs/fscache/volume.c index fc3dd3bc851d..734d17f404e7 100644 --- a/fs/fscache/volume.c +++ b/fs/fscache/volume.c @@ -281,6 +281,11 @@ static void fscache_create_volume_work(struct work_struct *work) fscache_access_acquire_volume_end); clear_bit_unlock(FSCACHE_VOLUME_CREATING, &volume->flags); + /* + * Paired with barrier in wait_on_bit(). Check wake_up_bit() and + * waitqueue_active() for details. + */ + smp_mb__after_atomic(); wake_up_bit(&volume->flags, FSCACHE_VOLUME_CREATING); fscache_put_volume(volume, fscache_volume_put_create_work); }