Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754200AbaF3Dum (ORCPT ); Sun, 29 Jun 2014 23:50:42 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:34000 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751552AbaF3Duk (ORCPT ); Sun, 29 Jun 2014 23:50:40 -0400 Message-ID: <53B0DE84.40206@huawei.com> Date: Mon, 30 Jun 2014 11:50:28 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: Tejun Heo CC: LKML , Cgroups , Greg Kroah-Hartman Subject: [PATCH v3 2/3] kernfs: introduce kernfs_pin_sb() References: <53B0DE66.5080100@huawei.com> In-Reply-To: <53B0DE66.5080100@huawei.com> Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.18.230] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org kernfs_pin_sb() tries to get a refcnt of the superblock. This will be used by cgroupfs. v2: - make kernfs_pin_sb() return the superblock. - drop kernfs_drop_sb(). [ This is a prerequisite for a bugfix. ] Cc: # 3.15 Acked-by: Greg Kroah-Hartman Signed-off-by: Li Zefan --- fs/kernfs/mount.c | 27 +++++++++++++++++++++++++++ include/linux/kernfs.h | 1 + 2 files changed, 28 insertions(+) diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c index f25a7c0..616c5c4 100644 --- a/fs/kernfs/mount.c +++ b/fs/kernfs/mount.c @@ -210,6 +210,33 @@ void kernfs_kill_sb(struct super_block *sb) kernfs_put(root_kn); } +/** + * kernfs_pin_sb: try to pin the superblock associated with a kernfs_root + * @kernfs_root: the kernfs_root in question + * @ns: the namespace tag + * + * Pin the superblock so the superblock won't be destroyed in subsequent + * operations. Return NULL if there's no superblock associated to this + * kernfs_root, or -EINVAL if the superblock is being freed. + */ +struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns) +{ + struct kernfs_super_info *info; + struct super_block *sb = NULL; + + mutex_lock(&kernfs_mutex); + list_for_each_entry(info, &root->supers, node) { + if (info->ns == ns) { + sb = info->sb; + if (!atomic_inc_not_zero(&info->sb->s_active)) + sb = ERR_PTR(-EINVAL); + break; + } + } + mutex_unlock(&kernfs_mutex); + return sb; +} + void __init kernfs_init(void) { kernfs_node_cache = kmem_cache_create("kernfs_node_cache", diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h index 589318b..9096296 100644 --- a/include/linux/kernfs.h +++ b/include/linux/kernfs.h @@ -287,6 +287,7 @@ struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags, struct kernfs_root *root, bool *new_sb_created, const void *ns); void kernfs_kill_sb(struct super_block *sb); +struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns); void kernfs_init(void); -- 1.8.0.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/