Bug 52791

Overview
----------------------

When mounting a CIFS share from a Microsoft Windows 7 or Windows Server 2008 (R1 or R2) system, the number of hard links of both directories and (under certain circumstances) ordinary files is wrong (always 0), no matter what the mount options are. Mounts from Windows 2003 Server and older are set correctly.

Steps to Reproduce
----------------------

1. mount a share from a Windows 7/2008 system to /mnt
   (mount option [no]unix has no effect)
2. ls -la /mnt   or    stat /mnt

Actual Results
----------------------

Directories on the share have the type "directory" (as reported by ls and stat) but a hard link count of 0.

Expected Results
----------------------

The hard link count for any directory should always be at least 2.

Build Date & Platform
----------------------

kernel version 3.7.1, built on January 10th, on an Ubuntu kernel 3.6.5 (custom compiled), x86_64, with gcc version 4.6.3-1ubuntu5.

Additional Information
----------------------

Local processes, especially the Bash, don't bother about the link count. Accessing files and listing directories, changing into them etc. are no problem. 

Samba, however is probably just one example of software relying on the number of hard links for its own purposes. For example, it treats directories with a 0 hard link count as ordinary files with size 0 (Samba clients cannot "click-change" into them, but they can access them directly), and files with 0 link count are presented to the client but inaccessible. See Demonstration below.

Workaround:

Any combination of mount options ([no]unix, [no]serverino, ...) yields the same results concerning the hard link count.

Patching the function cifs_fattr_to_inode works, although it doesn't seem to do anything different than the several other places in inode.c (e. g. cifs_all_info_to_fattr) that set cf_nlink.

*** linux-3.X.X-ORIGINAL/fs/cifs/inode.c 2012-12-06 14:58:18.248221824 +0100
--- linux-3.X.X/fs/cifs/inode.c 2013-01-10 14:02:38.367733296 +0100
***************
*** 132,138 ****
        inode->i_mtime = fattr->cf_mtime;
        inode->i_ctime = fattr->cf_ctime;
        inode->i_rdev = fattr->cf_rdev;
!       set_nlink(inode, fattr->cf_nlink);
        inode->i_uid = fattr->cf_uid;
        inode->i_gid = fattr->cf_gid;
--- 132,141 ----
        inode->i_mtime = fattr->cf_mtime;
        inode->i_ctime = fattr->cf_ctime;
        inode->i_rdev = fattr->cf_rdev;
!       if (fattr->cf_cifsattrs & ATTR_DIRECTORY)
!               set_nlink(inode, 2);
!       else
!               set_nlink(inode, 1);
        inode->i_uid = fattr->cf_uid;
        inode->i_gid = fattr->cf_gid;

In other words, the following piece of code in the current kernel does not work, as the link count cf_nlink seems to be reset to 0 somewhere else:

static void 
cifs_all_info_to_fattr(struct cifs_fattr *fattr, FILE_ALL_INFO *info,
                       struct cifs_sb_info *cifs_sb, bool adjust_tz)
{
...
        if (fattr->cf_cifsattrs & ATTR_DIRECTORY) {
                fattr->cf_mode = S_IFDIR | cifs_sb->mnt_dir_mode;
                fattr->cf_dtype = DT_DIR;
                /*
                 * Server can return wrong NumberOfLinks value for directories
                 * when Unix extensions are disabled - fake it.
                 */
                fattr->cf_nlink = 2;

Demonstration:

The following is a demonstration with kernel version 3.6.5, however the problem is still present in the current version 3.7.1.

root@log002:~# uname -r -m
3.6.5 x86_64
root@log002:~# mount.cifs -V
mount.cifs version: 5.7
root@log002:~# mount.cifs //sas003/testshare /mnt/testshare -o
serverino,user=administrator
Password for administrator@//sas003/testshare:
root@log002:~# ls -lai /mnt/testshare/
total 5
792352059440498915 drwxr-xr-x 2 root root    0 Nov  1 13:28 .
            917508 drwxr-xr-x 8 root root 4096 Nov  1 13:29 ..
                 3 drwxr-xr-x 0 root root    0 Nov  1 13:27 dir1
                 4 drwxr-xr-x 0 root root    0 Nov  1 13:28 dir2
                 5 -rwxr-xr-x 1 root root   15 Nov  1 13:27 file1.txt
                 6 -rwxr-xr-x 1 root root   22 Nov  1 13:28 file2.txt
root@log002:~# ls -lai /mnt/testshare/dir1
total 1
                 3 drwxr-xr-x 2 root root  0 Nov  1 13:27 .
792352059440498915 drwxr-xr-x 2 root root  0 Nov  1 13:28 ..
                 7 -rwxr-xr-x 1 root root 15 Nov  1 13:27 file_in_dir1.txt
root@log002:~# stat /mnt/testshare/dir1
  File: `/mnt/testshare/dir1'
  Size: 0               Blocks: 0          IO Block: 16384  directory
Device: 13h/19d Inode: 3           Links: 2
Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2012-11-04 16:50:36.564250000 +0100
Modify: 2012-11-01 13:27:59.035250000 +0100
Change: 2012-11-01 13:27:59.035250000 +0100
 Birth: -
root@log002:~#

This is what the Samba server (any version really) delivers to the client:

root@log002:~# smbclient //log002/testthis
Enter root's password: (empty)
Domain=[INTERNAL] OS=[Unix] Server=[Samba 3.6.3]
Server not using user level security and no password supplied.
smb: \> dir
  .                                   D        0  Thu Nov  1 13:28:24 2012
  ..                                  D        0  Thu Nov  1 13:29:23 2012
  dir1                                         0  Thu Nov  1 13:27:59 2012
  dir2                                         0  Thu Nov  1 13:28:04 2012
  file1.txt                           A       15  Thu Nov  1 13:27:43 2012
  file2.txt                           A       22  Thu Nov  1 13:28:32 2012

                64636 blocks of size 131072. 24954 blocks available
smb: \> cd dir1
smb: \dir1\> dir
  .                                   D        0  Thu Nov  1 13:27:59 2012
  ..                                  D        0  Thu Nov  1 13:28:24 2012
  file_in_dir1.txt                    A       15  Thu Nov  1 13:27:43 2012

                64636 blocks of size 131072. 24954 blocks available
smb: \dir1\>
root@log002:~#