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Thu, 19 Aug 2021 18:18:52 +0000 From: Anand Jain To: linux-btrfs@vger.kernel.org Cc: dsterba@suse.com, l@damenly.su Subject: [PATCH 1/3] btrfs: fix comment about the btrfs_show_devname Date: Fri, 20 Aug 2021 02:18:12 +0800 Message-Id: <26445e25588c8216cd5b7dcc453bf42dd4707739.1629396187.git.anand.jain@oracle.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: References: X-ClientProxiedBy: SG2PR01CA0114.apcprd01.prod.exchangelabs.com (2603:1096:4:40::18) To MN2PR10MB4128.namprd10.prod.outlook.com (2603:10b6:208:1d2::24) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from localhost.localdomain (203.116.164.13) by SG2PR01CA0114.apcprd01.prod.exchangelabs.com (2603:1096:4:40::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4436.19 via Frontend Transport; Thu, 19 Aug 2021 18:18:34 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: bb0e5e38-841c-4702-d4ca-08d9633dcbf4 X-MS-TrafficTypeDiagnostic: MN2PR10MB3966: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:514; 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This patch fixes a stale comment about the function btrfs_show_devname. Signed-off-by: Anand Jain --- fs/btrfs/volumes.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 9cb4ed90888d..91b8422b3f67 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -2278,10 +2278,7 @@ void btrfs_destroy_dev_replace_tgtdev(struct btrfs_device *tgtdev) /* * The update_dev_time() with in btrfs_scratch_superblocks() - * may lead to a call to btrfs_show_devname() which will try - * to hold device_list_mutex. And here this device - * is already out of device list, so we don't have to hold - * the device_list_mutex lock. + * may lead to a call to btrfs_show_devname(). */ btrfs_scratch_superblocks(tgtdev->fs_info, tgtdev->bdev, tgtdev->name->str); From patchwork Thu Aug 19 18:18:13 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Anand Jain X-Patchwork-Id: 12447735 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MSGID_FROM_MTA_HEADER,SPF_HELO_NONE, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5129CC432BE for ; Thu, 19 Aug 2021 18:19:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 39D31610A1 for ; 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Thu, 19 Aug 2021 18:18:54 +0000 From: Anand Jain To: linux-btrfs@vger.kernel.org Cc: dsterba@suse.com, l@damenly.su Subject: [PATCH RFC 2/3] btrfs: consolidate device_list_mutex in prepare_sprout to its parent Date: Fri, 20 Aug 2021 02:18:13 +0800 Message-Id: <8b8e72c87d0ee97da1b2e243a24b68d84d0ac3b9.1629396187.git.anand.jain@oracle.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: References: X-ClientProxiedBy: SG2PR01CA0114.apcprd01.prod.exchangelabs.com (2603:1096:4:40::18) To MN2PR10MB4128.namprd10.prod.outlook.com (2603:10b6:208:1d2::24) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from localhost.localdomain (203.116.164.13) by SG2PR01CA0114.apcprd01.prod.exchangelabs.com (2603:1096:4:40::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4436.19 via Frontend Transport; Thu, 19 Aug 2021 18:18:52 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 01d69ea8-78ef-4f1b-f4b9-08d9633dcd69 X-MS-TrafficTypeDiagnostic: MN2PR10MB3966: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:8273; 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Both btrfs_prepare_sprout() and btrfs_init_new_device() needs device_list_mutex. But they are holding it sequentially, thus creates a small window to an opportunity to race. Close this opportunity and hold device_list_mutex common to both btrfs_init_new_device() and btrfs_prepare_sprout(). Signed-off-by: Anand Jain --- RFC because I haven't identified the other thread which could race with this, but still does this cleanup makes sense? fs/btrfs/volumes.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 91b8422b3f67..f490d1897c56 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -2366,6 +2366,8 @@ static int btrfs_prepare_sprout(struct btrfs_fs_info *fs_info) u64 super_flags; lockdep_assert_held(&uuid_mutex); + lockdep_assert_held(&fs_devices->device_list_mutex); + if (!fs_devices->seeding) return -EINVAL; @@ -2397,7 +2399,6 @@ static int btrfs_prepare_sprout(struct btrfs_fs_info *fs_info) INIT_LIST_HEAD(&seed_devices->alloc_list); mutex_init(&seed_devices->device_list_mutex); - mutex_lock(&fs_devices->device_list_mutex); list_splice_init_rcu(&fs_devices->devices, &seed_devices->devices, synchronize_rcu); list_for_each_entry(device, &seed_devices->devices, dev_list) @@ -2413,7 +2414,6 @@ static int btrfs_prepare_sprout(struct btrfs_fs_info *fs_info) generate_random_uuid(fs_devices->fsid); memcpy(fs_devices->metadata_uuid, fs_devices->fsid, BTRFS_FSID_SIZE); memcpy(disk_super->fsid, fs_devices->fsid, BTRFS_FSID_SIZE); - mutex_unlock(&fs_devices->device_list_mutex); super_flags = btrfs_super_flags(disk_super) & ~BTRFS_SUPER_FLAG_SEEDING; @@ -2588,6 +2588,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path device->dev_stats_valid = 1; set_blocksize(device->bdev, BTRFS_BDEV_BLOCKSIZE); + mutex_lock(&fs_devices->device_list_mutex); if (seeding_dev) { btrfs_clear_sb_rdonly(sb); ret = btrfs_prepare_sprout(fs_info); @@ -2599,7 +2600,6 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path device->fs_devices = fs_devices; - mutex_lock(&fs_devices->device_list_mutex); mutex_lock(&fs_info->chunk_mutex); list_add_rcu(&device->dev_list, &fs_devices->devices); list_add(&device->dev_alloc_list, &fs_devices->alloc_list); From patchwork Thu Aug 19 18:18:14 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Anand Jain X-Patchwork-Id: 12447731 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MSGID_FROM_MTA_HEADER,SPF_HELO_NONE, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5E501C4338F for ; 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Thu, 19 Aug 2021 18:18:56 +0000 From: Anand Jain To: linux-btrfs@vger.kernel.org Cc: dsterba@suse.com, l@damenly.su Subject: [PATCH RFC 3/3] btrfs: use latest_bdev in btrfs_show_devname Date: Fri, 20 Aug 2021 02:18:14 +0800 Message-Id: <9a06b04b9003f86c3300e497b35b0ef0310c84c0.1629396187.git.anand.jain@oracle.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: References: X-ClientProxiedBy: SG2PR01CA0114.apcprd01.prod.exchangelabs.com (2603:1096:4:40::18) To MN2PR10MB4128.namprd10.prod.outlook.com (2603:10b6:208:1d2::24) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from localhost.localdomain (203.116.164.13) by SG2PR01CA0114.apcprd01.prod.exchangelabs.com (2603:1096:4:40::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4436.19 via Frontend Transport; Thu, 19 Aug 2021 18:18:54 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 60bc09ef-055b-4e61-19fd-08d9633dcec5 X-MS-TrafficTypeDiagnostic: MN2PR10MB3966: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:10000; 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That means we could use the latest_bdev to show the device name in /proc/self/mounts. So this patch makes that change. Signed-off-by: Anand Jain --- RFC because 1. latest_bdev might not be the lowest devid but, we showed the lowest devid in /proc/self/mount. 2. The device's path is not shown now but, previously we did. So does these break ABI? Maybe yes for 2 howabout for 1 above? fs/btrfs/super.c | 25 +++---------------------- 1 file changed, 3 insertions(+), 22 deletions(-) diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 1f9dd1a4faa3..4ad3fe174c41 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -2464,30 +2464,11 @@ static int btrfs_unfreeze(struct super_block *sb) static int btrfs_show_devname(struct seq_file *m, struct dentry *root) { struct btrfs_fs_info *fs_info = btrfs_sb(root->d_sb); - struct btrfs_device *dev, *first_dev = NULL; + char name[BDEVNAME_SIZE]; - /* - * Lightweight locking of the devices. We should not need - * device_list_mutex here as we only read the device data and the list - * is protected by RCU. Even if a device is deleted during the list - * traversals, we'll get valid data, the freeing callback will wait at - * least until the rcu_read_unlock. - */ - rcu_read_lock(); - list_for_each_entry_rcu(dev, &fs_info->fs_devices->devices, dev_list) { - if (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state)) - continue; - if (!dev->name) - continue; - if (!first_dev || dev->devid < first_dev->devid) - first_dev = dev; - } + seq_escape(m, bdevname(fs_info->fs_devices->latest_bdev, name), + " \t\n\\"); - if (first_dev) - seq_escape(m, rcu_str_deref(first_dev->name), " \t\n\\"); - else - WARN_ON(1); - rcu_read_unlock(); return 0; }