lkml.org 
[lkml]   [2008]   [Jul]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 11/17] configfs: Protect configfs_dirent s_links list mutations
Date
From: Louis Rilling <Louis.Rilling@kerlabs.com>

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 <Louis.Rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
---
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 2619f48..a08e5c2 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 676c84c..faeb441 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);
--
1.5.4.1


\
 
 \ /
  Last update: 2008-07-15 00:09    [W:0.140 / U:0.724 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site