Description of problem:
In an append only dir, a open(2) call without O_RDONLY and O_APPEND will return -EPERM, but after the call new file is created.

Version-Release number of selected component (if applicable):
kernel-2.6.32-211.el6

How reproducible:
100%

Steps to Reproduce:
1. mkdir /mnt/ext4/append-only
2. chattr +a /mnt/ext4/append-only
3. ./test /mnt/ext4/append-only/testfile (touch /mnt/ext4/append-only/testfile will also work, but touch won't return error, you have to strace touch and search for open, it returns -EPERM)

# cat test.c
#include <stdio.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <errno.h>

int main(int argc, char *argv[])
{
        int fd;
        fd = open(argv[1], O_RDWR|O_CREAT, 0666);
        if (fd == -1)
                perror("open failed");
        exit(errno);
}
  
Actual results:
[root@fstest xfstests]# mkdir -p /mnt/ext4/append-only
[root@fstest xfstests]# chattr +a /mnt/ext4/append-only
[root@fstest xfstests]# lsattr /mnt/ext4/
--------------- /mnt/ext4/lost+found
-----a-------e- /mnt/ext4/append-only
[root@fstest xfstests]# ./test /mnt/ext4/append-only/testfile
open failed: Operation not permitted
[root@fstest xfstests]# ls -l /mnt/ext4/append-only/testfile
-rw-r--r--. 1 root root 0 Oct 26 16:07 /mnt/ext4/append-only/testfile
[root@fstest xfstests]# lsattr /mnt/ext4/append-only/testfile
-----a-------e- /mnt/ext4/append-only/testfile

Expected results:
open(2) return success or new file is not created at all

Additional info:
xfs will create new file with no problem
btrfs will fail too

Not sure if it's really a bug, but some kind of inconsistent