Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753307AbaF3OTM (ORCPT ); Mon, 30 Jun 2014 10:19:12 -0400 Received: from mail-qa0-f42.google.com ([209.85.216.42]:38140 "EHLO mail-qa0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751223AbaF3OTK (ORCPT ); Mon, 30 Jun 2014 10:19:10 -0400 Date: Mon, 30 Jun 2014 10:19:06 -0400 From: Tejun Heo To: Li Zefan Cc: LKML , Cgroups , Greg Kroah-Hartman Subject: Re: [PATCH v3 2/3] kernfs: introduce kernfs_pin_sb() Message-ID: <20140630141906.GB14807@htj.dyndns.org> References: <53B0DE66.5080100@huawei.com> <53B0DE84.40206@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53B0DE84.40206@huawei.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Applied to cgroup/for-3.16-fixes with minor updates. Thanks. ------ 8< ------ >From 4e26445faad366d67d7723622bf6a60a6f0f5993 Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Mon, 30 Jun 2014 11:50:28 +0800 Subject: [PATCH 2/3] kernfs: introduce kernfs_pin_sb() 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(). tj: Updated the comment a bit. [ This is a prerequisite for a bugfix. ] Cc: # 3.15 Acked-by: Greg Kroah-Hartman Signed-off-by: Li Zefan Signed-off-by: Tejun Heo --- fs/kernfs/mount.c | 30 ++++++++++++++++++++++++++++++ include/linux/kernfs.h | 1 + 2 files changed, 31 insertions(+) diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c index d171b98..f973ae9 100644 --- a/fs/kernfs/mount.c +++ b/fs/kernfs/mount.c @@ -211,6 +211,36 @@ 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. This can be used to block ->kill_sb() which may be useful + * for kernfs users which dynamically manage superblocks. + * + * Returns 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 17aa1cc..20f4935 100644 --- a/include/linux/kernfs.h +++ b/include/linux/kernfs.h @@ -304,6 +304,7 @@ struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags, struct kernfs_root *root, unsigned long magic, 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); -- 1.9.3 -- 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/