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authorTejun Heo <htejun@gmail.com>2007-06-11 14:04:01 +0900
committerGreg Kroah-Hartman <gregkh@suse.de>2007-06-12 16:08:47 -0700
commitdd14cbc994709a1c5a64ed3621f583c49a27e521 (patch)
treee48d38b7450661907c7b75490504c7f70b04d6cc /fs/sysfs/inode.c
parent6aa054aadfea613a437ad0b15d38eca2b963fc0a (diff)
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sysfs: fix race condition around sd->s_dentry, take#2
Allowing attribute and symlink dentries to be reclaimed means sd->s_dentry can change dynamically. However, updates to the field are unsynchronized leading to race conditions. This patch adds sysfs_lock and use it to synchronize updates to sd->s_dentry. Due to the locking around ->d_iput, the check in sysfs_drop_dentry() is complex. sysfs_lock only protect sd->s_dentry pointer itself. The validity of the dentry is protected by dcache_lock, so whether dentry is alive or not can only be tested while holding both locks. This is minimal backport of sysfs_drop_dentry() rewrite in devel branch. Signed-off-by: Tejun Heo <htejun@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'fs/sysfs/inode.c')
-rw-r--r--fs/sysfs/inode.c18
1 files changed, 17 insertions, 1 deletions
diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index 38bbe071cc1..5266eec15f6 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -246,9 +246,23 @@ static inline void orphan_all_buffers(struct inode *node)
*/
void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
{
- struct dentry * dentry = sd->s_dentry;
+ struct dentry *dentry = NULL;
struct inode *inode;
+ /* We're not holding a reference to ->s_dentry dentry but the
+ * field will stay valid as long as sysfs_lock is held.
+ */
+ spin_lock(&sysfs_lock);
+ spin_lock(&dcache_lock);
+
+ /* dget dentry if it's still alive */
+ if (sd->s_dentry && sd->s_dentry->d_inode)
+ dentry = dget_locked(sd->s_dentry);
+
+ spin_unlock(&dcache_lock);
+ spin_unlock(&sysfs_lock);
+
+ /* drop dentry */
if (dentry) {
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
@@ -268,6 +282,8 @@ void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
}
+
+ dput(dentry);
}
}