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 6760EECAAA1 for ; Mon, 5 Sep 2022 03:57:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235677AbiIED5b (ORCPT ); Sun, 4 Sep 2022 23:57:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54442 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231540AbiIED52 (ORCPT ); Sun, 4 Sep 2022 23:57:28 -0400 Received: from out20-158.mail.aliyun.com (out20-158.mail.aliyun.com [115.124.20.158]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 82D4224F11 for ; Sun, 4 Sep 2022 20:57:26 -0700 (PDT) X-Alimail-AntiSpam: AC=CONTINUE;BC=0.04442586|-1;BR=01201311R191S27rulernew998_84748_2000303;CH=blue;DM=|CONTINUE|false|;DS=CONTINUE|ham_regular_dialog|0.365067-0.0122703-0.622663;FP=0|0|0|0|0|-1|-1|-1;HT=ay29a033018047188;MF=wangyugui@e16-tech.com;NM=1;PH=DS;RN=1;RT=1;SR=0;TI=SMTPD_---.P80ExQK_1662350243; Received: from 192.168.2.112(mailfrom:wangyugui@e16-tech.com fp:SMTPD_---.P80ExQK_1662350243) by smtp.aliyun-inc.com; Mon, 05 Sep 2022 11:57:24 +0800 Date: Mon, 05 Sep 2022 11:57:26 +0800 From: Wang Yugui To: linux-btrfs@vger.kernel.org Subject: Re: [PATCH v2] btrfs: slience the sparse warn of rcu_string In-Reply-To: <20220824051208.19924-1-wangyugui@e16-tech.com> References: <20220824051208.19924-1-wangyugui@e16-tech.com> Message-Id: <20220905115726.6C63.409509F4@e16-tech.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.75.04 [en] Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Hi, > slience the sparse warn of rcu_string reported by 'make C=1' > > warning example: > fs/btrfs/volumes.c:2300:41: warning: incorrect type in argument 3 (different address spaces) > fs/btrfs/volumes.c:2300:41: expected char const *device_path > fs/btrfs/volumes.c:2300:41: got char [noderef] __rcu * I'm sorry that some new WARNING is triggered when lockdep(CONFIG_PROVE_LOCKING/...) check is enabled. [ 112.742722] ============================= [ 112.746835] WARNING: suspicious RCU usage [ 112.750917] 6.0.0-4.0.el7.x86_64 #1 Not tainted [ 112.755540] ----------------------------- [ 112.759624] fs/btrfs/volumes.c:918 suspicious rcu_dereference_check() usage! [ 112.766776] other info that might help us debug this: [ 112.774921] rcu_scheduler_active = 2, debug_locks = 1 [ 112.781566] 2 locks held by mount/1725: [ 112.785471] #0: ffffffffc50592a8 (uuid_mutex){+.+.}-{3:3}, at: btrfs_mount_root+0xfe/0x520 [btrfs] [ 112.794763] #1: ffffa1147bf068e0 (&fs_devs->device_list_mutex){+.+.}-{3:3}, at: device_list_add+0x28d/0x830 [btrfs] The fix is yet not clear, we may need rcu_read_lock() just like 3181faa85bda3dc3f5e630a1846526c9caaa38e3 (cfq-iosched: fix a rcu warning) Best Regards Wang Yugui (wangyugui@e16-tech.com) 2022/09/05 > Reviewed-by: Johannes Thumshirn > Signed-off-by: Wang Yugui > --- > changes since v1: > add a warn example. > add 'Reviewed-by: Johannes Thumshirn'. > > fs/btrfs/dev-replace.c | 2 +- > fs/btrfs/volumes.c | 14 +++++++------- > 2 files changed, 8 insertions(+), 8 deletions(-) > > diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c > index 70d001d..b30930e 100644 > --- a/fs/btrfs/dev-replace.c > +++ b/fs/btrfs/dev-replace.c > @@ -1006,7 +1006,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info, > btrfs_sysfs_update_devid(tgt_device); > if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &src_device->dev_state)) > btrfs_scratch_superblocks(fs_info, src_device->bdev, > - src_device->name->str); > + rcu_str_deref(src_device->name)); > > /* write back the superblocks */ > trans = btrfs_start_transaction(root, 0); > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > index 9481108..2cd261c 100644 > --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -390,7 +390,7 @@ static struct btrfs_fs_devices *alloc_fs_devices(const u8 *fsid, > void btrfs_free_device(struct btrfs_device *device) > { > WARN_ON(!list_empty(&device->post_commit_list)); > - rcu_string_free(device->name); > + rcu_string_free(rcu_dereference(device->name)); > extent_io_tree_release(&device->alloc_state); > btrfs_destroy_dev_zone_info(device); > kfree(device); > @@ -640,7 +640,7 @@ static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices, > if (!device->name) > return -EINVAL; > > - ret = btrfs_get_bdev_and_sb(device->name->str, flags, holder, 1, > + ret = btrfs_get_bdev_and_sb(rcu_str_deref(device->name), flags, holder, 1, > &bdev, &disk_super); > if (ret) > return ret; > @@ -908,7 +908,7 @@ static noinline struct btrfs_device *device_list_add(const char *path, > disk_super->fsid, devid, found_transid, path, > current->comm, task_pid_nr(current)); > > - } else if (!device->name || strcmp(device->name->str, path)) { > + } else if (!device->name || strcmp(rcu_str_deref(device->name), path)) { > /* > * When FS is already mounted. > * 1. If you are here and if the device->name is NULL that > @@ -978,7 +978,7 @@ static noinline struct btrfs_device *device_list_add(const char *path, > mutex_unlock(&fs_devices->device_list_mutex); > return ERR_PTR(-ENOMEM); > } > - rcu_string_free(device->name); > + rcu_string_free(rcu_dereference(device->name)); > rcu_assign_pointer(device->name, name); > if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state)) { > fs_devices->missing_devices--; > @@ -1035,7 +1035,7 @@ static struct btrfs_fs_devices *clone_fs_devices(struct btrfs_fs_devices *orig) > * uuid mutex so nothing we touch in here is going to disappear. > */ > if (orig_dev->name) { > - name = rcu_string_strdup(orig_dev->name->str, > + name = rcu_string_strdup(rcu_str_deref(orig_dev->name), > GFP_KERNEL); > if (!name) { > btrfs_free_device(device); > @@ -2217,7 +2217,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, > */ > if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) { > btrfs_scratch_superblocks(fs_info, device->bdev, > - device->name->str); > + rcu_str_deref(device->name)); > if (device->bdev) { > sync_blockdev(device->bdev); > invalidate_bdev(device->bdev); > @@ -2332,7 +2332,7 @@ void btrfs_destroy_dev_replace_tgtdev(struct btrfs_device *tgtdev) > mutex_unlock(&fs_devices->device_list_mutex); > > btrfs_scratch_superblocks(tgtdev->fs_info, tgtdev->bdev, > - tgtdev->name->str); > + rcu_str_deref(tgtdev->name)); > > btrfs_close_bdev(tgtdev); > synchronize_rcu(); > -- > 2.36.2