cifs: add "mfsymlinks" mount option

This is the start for an implementation of "Minshall+French Symlinks"
(see http://wiki.samba.org/index.php/UNIX_Extensions#Minshall.2BFrench_symlinks).

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>

3 files changed, 18 insertions, 0 deletions

diff --git a/fs/cifs/README b/fs/cifs/README
index 7099a526f775..ee68d1036544 100644
--- a/fs/cifs/README
+++ b/fs/cifs/README
@@ -527,6 +527,11 @@ A partial list of the supported mount options follows:
                 SFU does).  In the future the bottom 9 bits of the
                 mode also will be emulated using queries of the security
                 descriptor (ACL).
+ mfsymlinks     Enable support for Minshall+French symlinks
+                (see http://wiki.samba.org/index.php/UNIX_Extensions#Minshall.2BFrench_symlinks)
+                This option is ignored when specified together with the
+                'sfu' option. Minshall+French symlinks are used even if
+                the server supports the CIFS Unix Extensions.
  sign           Must use packet signing (helps avoid unwanted data modification
                 by intermediate systems in the route).  Note that signing
                 does not work with lanman or plaintext authentication.
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 1b6ddd6f760f..52e89ea07458 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -441,6 +441,8 @@ cifs_show_options(struct seq_file *s, struct vfsmount *m)
                 seq_printf(s, ",dynperm");
         if (m->mnt_sb->s_flags & MS_POSIXACL)
                 seq_printf(s, ",acl");
+        if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS)
+                seq_printf(s, ",mfsymlinks");
 
         seq_printf(s, ",rsize=%d", cifs_sb->rsize);
         seq_printf(s, ",wsize=%d", cifs_sb->wsize);
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index fa884520fb84..435b912f5de5 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -100,6 +100,7 @@ struct smb_vol {
         bool noautotune:1;
         bool nostrictsync:1; /* do not force expensive SMBflush on every sync */
         bool fsc:1;     /* enable fscache */
+        bool mfsymlinks:1; /* use Minshall+French Symlinks */
         unsigned int rsize;
         unsigned int wsize;
         bool sockopt_tcp_nodelay:1;
@@ -1342,6 +1343,8 @@ cifs_parse_mount_options(char *options, const char *devname,
                                 "/proc/fs/cifs/LookupCacheEnabled to 0\n");
                 } else if (strnicmp(data, "fsc", 3) == 0) {
                         vol->fsc = true;
+                } else if (strnicmp(data, "mfsymlinks", 10) == 0) {
+                        vol->mfsymlinks = true;
                 } else
                         printk(KERN_WARNING "CIFS: Unknown mount option %s\n",
                                                 data);
@@ -2554,6 +2557,14 @@ static void setup_cifs_sb(struct smb_vol *pvolume_info,
                 cFYI(1, "mounting share using direct i/o");
                 cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_DIRECT_IO;
         }
+        if (pvolume_info->mfsymlinks) {
+                if (pvolume_info->sfu_emul) {
+                        cERROR(1,  "mount option mfsymlinks ignored if sfu "
+                                   "mount option is used");
+                } else {
+                        cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_MF_SYMLINKS;
+                }
+        }
 
         if ((pvolume_info->cifs_acl) && (pvolume_info->dynperm))
                 cERROR(1, "mount option dynperm ignored if cifsacl "