From 5301a77da2da1e4c22573e0e8d394a653b8ad9f9 Mon Sep 17 00:00:00 2001 From: Louis Rilling Date: Mon, 16 Jun 2008 19:00:59 +0200 Subject: [PATCH] configfs: Protect configfs_dirent s_links list mutations Symlinks to a config_item are listed under its configfs_dirent s_links, but the list mutations are not protected by any common lock. This patch uses the configfs_dirent_lock spinlock to add the necessary protection. Note: we should also protect the list_empty() test in configfs_detach_prep() but 1/ the lock should not be released immediately because nothing would prevent the list from being filled after a successful list_empty() test, making the problem tricky, 2/ this will be solved by the rmdir() vs rename() deadlock bugfix. Signed-off-by: Louis Rilling Signed-off-by: Joel Becker --- fs/configfs/dir.c | 5 +++-- fs/configfs/symlink.c | 8 ++++++-- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c index 2619f485bc3..a08e5c2f25e 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -37,10 +37,11 @@ DECLARE_RWSEM(configfs_rename_sem); /* * Protects mutations of configfs_dirent linkage together with proper i_mutex + * Also protects mutations of symlinks linkage to target configfs_dirent * Mutators of configfs_dirent linkage must *both* have the proper inode locked * and configfs_dirent_lock locked, in that order. - * This allows one to safely traverse configfs_dirent trees without having to - * lock inodes. + * This allows one to safely traverse configfs_dirent trees and symlinks without + * having to lock inodes. */ DEFINE_SPINLOCK(configfs_dirent_lock); diff --git a/fs/configfs/symlink.c b/fs/configfs/symlink.c index 676c84c416d..faeb4417a10 100644 --- a/fs/configfs/symlink.c +++ b/fs/configfs/symlink.c @@ -77,12 +77,15 @@ static int create_link(struct config_item *parent_item, sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL); if (sl) { sl->sl_target = config_item_get(item); - /* FIXME: needs a lock, I'd bet */ + spin_lock(&configfs_dirent_lock); list_add(&sl->sl_list, &target_sd->s_links); + spin_unlock(&configfs_dirent_lock); ret = configfs_create_link(sl, parent_item->ci_dentry, dentry); if (ret) { + spin_lock(&configfs_dirent_lock); list_del_init(&sl->sl_list); + spin_unlock(&configfs_dirent_lock); config_item_put(item); kfree(sl); } @@ -186,8 +189,9 @@ int configfs_unlink(struct inode *dir, struct dentry *dentry) type->ct_item_ops->drop_link(parent_item, sl->sl_target); - /* FIXME: Needs lock */ + spin_lock(&configfs_dirent_lock); list_del_init(&sl->sl_list); + spin_unlock(&configfs_dirent_lock); /* Put reference from create_link() */ config_item_put(sl->sl_target);