reiserfs: Relax lock on xattr removing

When we remove an xattr, we call lookup_and_delete_xattr()
that takes some private xattr inodes mutexes. But we hold
the reiserfs lock at this time, which leads to dependency
inversions.

We can safely call lookup_and_delete_xattr() without the
reiserfs lock, where xattr inodes lookups only need the
xattr inodes mutexes.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Christian Kujau <lists@nerdbynature.de>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>

fs/reiserfs/xattr.c

@@ -451,7 +451,9 @@ static int lookup_and_delete_xattr(struct inode *inode, const char *name)
 	}
 
 	if (dentry->d_inode) {
+		reiserfs_write_lock(inode->i_sb);
 		err = xattr_unlink(xadir->d_inode, dentry);
+		reiserfs_write_unlock(inode->i_sb);
 		update_ctime(inode);
 	}
 
@@ -485,10 +487,14 @@ reiserfs_xattr_set_handle(struct reiserfs_transaction_handle *th,
 	if (get_inode_sd_version(inode) == STAT_DATA_V1)
 		return -EOPNOTSUPP;
 
-	if (!buffer)
-		return lookup_and_delete_xattr(inode, name);
-
 	reiserfs_write_unlock(inode->i_sb);
+
+	if (!buffer) {
+		err = lookup_and_delete_xattr(inode, name);
+		reiserfs_write_lock(inode->i_sb);
+		return err;
+	}
+
 	dentry = xattr_lookup(inode, name, flags);
 	if (IS_ERR(dentry)) {
 		reiserfs_write_lock(inode->i_sb);