CIFS: Fix wrong pos argument of cifs_find_lock_conflict

and use generic_file_aio_write rather than __generic_file_aio_write
in cifs_writev.

Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/file.c

@@ -2579,31 +2579,19 @@ cifs_writev(struct kiocb *iocb, const struct iovec *iov,
 	struct cifsInodeInfo *cinode = CIFS_I(inode);
 	struct TCP_Server_Info *server = tlink_tcon(cfile->tlink)->ses->server;
 	ssize_t rc = -EACCES;
+	loff_t lock_pos = pos;
 
-	BUG_ON(iocb->ki_pos != pos);
-
+	if (file->f_flags & O_APPEND)
+		lock_pos = i_size_read(inode);
 	/*
 	 * We need to hold the sem to be sure nobody modifies lock list
 	 * with a brlock that prevents writing.
 	 */
 	down_read(&cinode->lock_sem);
-	if (!cifs_find_lock_conflict(cfile, pos, iov_length(iov, nr_segs),
+	if (!cifs_find_lock_conflict(cfile, lock_pos, iov_length(iov, nr_segs),
 				     server->vals->exclusive_lock_type, NULL,
-				     CIFS_WRITE_OP)) {
-		mutex_lock(&inode->i_mutex);
-		rc = __generic_file_aio_write(iocb, iov, nr_segs,
-					       &iocb->ki_pos);
-		mutex_unlock(&inode->i_mutex);
-	}
-
-	if (rc > 0) {
-		ssize_t err;
-
-		err = generic_write_sync(file, iocb->ki_pos - rc, rc);
-		if (err < 0)
-			rc = err;
-	}
-
+				     CIFS_WRITE_OP))
+		rc = generic_file_aio_write(iocb, iov, nr_segs, pos);
 	up_read(&cinode->lock_sem);
 	return rc;
 }