reiserfs: call truncate_setsize under tailpack mutex

Prior to commit 0e4f6a791b (Fix reiserfs_file_release()), reiserfs
truncates serialized on i_mutex. They mostly still do, with the exception
of reiserfs_file_release. That blocks out other writers via the tailpack
mutex and the inode openers counter adjusted in reiserfs_file_open.

However, NFS will call reiserfs_setattr without having called ->open, so
we end up with a race when nfs is calling ->setattr while another
process is releasing the file. Ultimately, it triggers the
BUG_ON(inode->i_size != new_file_size) check in maybe_indirect_to_direct.

The solution is to pull the lock into reiserfs_setattr to encompass the
truncate_setsize call as well.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/reiserfs/inode.c

@@ -3422,8 +3422,14 @@ int reiserfs_setattr(struct dentry *dentry, struct iattr *attr)
 	    attr->ia_size != i_size_read(inode)) {
 		error = inode_newsize_ok(inode, attr->ia_size);
 		if (!error) {
+			/*
+			 * Could race against reiserfs_file_release
+			 * if called from NFS, so take tailpack mutex.
+			 */
+			mutex_lock(&REISERFS_I(inode)->tailpack);
 			truncate_setsize(inode, attr->ia_size);
-			reiserfs_vfs_truncate_file(inode);
+			reiserfs_truncate_file(inode, 1);
+			mutex_unlock(&REISERFS_I(inode)->tailpack);
 		}
 	}