1 files changed, 56 insertions, 0 deletions
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index edb30621b82..c6f3b697064 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -435,6 +435,62 @@ void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
 }
 
 /**
+ *	sysfs_drop_dentry - drop dentry for the specified sysfs_dirent
+ *	@sd: target sysfs_dirent
+ *
+ *	Drop dentry for @sd.  @sd must have been unlinked from its
+ *	parent on entry to this function such that it can't be looked
+ *	up anymore.
+ *
+ *	@sd->s_dentry which is protected with sysfs_assoc_lock points
+ *	to the currently associated dentry but we're not holding a
+ *	reference to it and racing with dput().  Grab dcache_lock and
+ *	verify dentry before dropping it.  If @sd->s_dentry is NULL or
+ *	dput() beats us, no need to bother.
+ */
+static void sysfs_drop_dentry(struct sysfs_dirent *sd)
+{
+	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_assoc_lock is held.
+	 */
+	spin_lock(&sysfs_assoc_lock);
+	spin_lock(&dcache_lock);
+
+	/* drop dentry if it's there and dput() didn't kill it yet */
+	if (sd->s_dentry && sd->s_dentry->d_inode) {
+		dentry = dget_locked(sd->s_dentry);
+		spin_lock(&dentry->d_lock);
+		__d_drop(dentry);
+		spin_unlock(&dentry->d_lock);
+	}
+
+	spin_unlock(&dcache_lock);
+	spin_unlock(&sysfs_assoc_lock);
+
+	dput(dentry);
+	/* XXX: unpin if directory, this will go away soon */
+	if (sysfs_type(sd) == SYSFS_DIR)
+		dput(dentry);
+
+	/* adjust nlink and update timestamp */
+	inode = ilookup(sysfs_sb, sd->s_ino);
+	if (inode) {
+		mutex_lock(&inode->i_mutex);
+
+		inode->i_ctime = CURRENT_TIME;
+		drop_nlink(inode);
+		if (sysfs_type(sd) == SYSFS_DIR)
+			drop_nlink(inode);
+
+		mutex_unlock(&inode->i_mutex);
+		iput(inode);
+	}
+}
+
+/**
  *	sysfs_addrm_finish - finish up sysfs_dirent add/remove
  *	@acxt: addrm context to finish up
  *