cifs: use Minshall+French symlink functions

If configured, Minshall+French Symlinks are used against
all servers. If the server supports UNIX Extensions,
we still create Minshall+French Symlinks on write,
but on read we fallback to UNIX Extension symlinks.

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

4 files changed, 47 insertions, 4 deletions

diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
index 9e771450c3b8..7fde52969896 100644
--- a/fs/cifs/cifs_fs_sb.h
+++ b/fs/cifs/cifs_fs_sb.h
@@ -36,6 +36,7 @@
 #define CIFS_MOUNT_NOPOSIXBRL   0x2000 /* mandatory not posix byte range lock */
 #define CIFS_MOUNT_NOSSYNC      0x4000 /* don't do slow SMBflush on every sync*/
 #define CIFS_MOUNT_FSCACHE      0x8000 /* local caching enabled */
+#define CIFS_MOUNT_MF_SYMLINKS  0x10000 /* Minshall+French Symlinks enabled */
 
 struct cifs_sb_info {
         struct cifsTconInfo *tcon;      /* primary mount */
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 93f77d438d3c..016975b8e6dd 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -332,6 +332,13 @@ int cifs_get_inode_info_unix(struct inode **pinode,
                 return rc;
         }
 
+        /* check for Minshall+French symlinks */
+        if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS) {
+                int tmprc = CIFSCheckMFSymlink(&fattr, full_path, cifs_sb, xid);
+                if (tmprc)
+                        cFYI(1, "CIFSCheckMFSymlink: %d", tmprc);
+        }
+
         if (*pinode == NULL) {
                 /* get new inode */
                 cifs_fill_uniqueid(sb, &fattr);
@@ -661,6 +668,13 @@ int cifs_get_inode_info(struct inode **pinode,
         if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_UNX_EMUL)
                 cifs_sfu_mode(&fattr, full_path, cifs_sb, xid);
 
+        /* check for Minshall+French symlinks */
+        if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS) {
+                tmprc = CIFSCheckMFSymlink(&fattr, full_path, cifs_sb, xid);
+                if (tmprc)
+                        cFYI(1, "CIFSCheckMFSymlink: %d", tmprc);
+        }
+
         if (!*pinode) {
                 *pinode = cifs_iget(sb, &fattr);
                 if (!*pinode)
diff --git a/fs/cifs/link.c b/fs/cifs/link.c
index 1b2a8c971995..cbf7b112287b 100644
--- a/fs/cifs/link.c
+++ b/fs/cifs/link.c
@@ -407,7 +407,8 @@ cifs_follow_link(struct dentry *direntry, struct nameidata *nd)
          * but there doesn't seem to be any harm in allowing the client to
          * read them.
          */
-        if (!(tcon->ses->capabilities & CAP_UNIX)) {
+        if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS)
+            && !(tcon->ses->capabilities & CAP_UNIX)) {
                 rc = -EACCES;
                 goto out;
         }
@@ -418,8 +419,21 @@ cifs_follow_link(struct dentry *direntry, struct nameidata *nd)
 
         cFYI(1, "Full path: %s inode = 0x%p", full_path, inode);
 
-        rc = CIFSSMBUnixQuerySymLink(xid, tcon, full_path, &target_path,
-                                     cifs_sb->local_nls);
+        rc = -EACCES;
+        /*
+         * First try Minshall+French Symlinks, if configured
+         * and fallback to UNIX Extensions Symlinks.
+         */
+        if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS)
+                rc = CIFSQueryMFSymLink(xid, tcon, full_path, &target_path,
+                                        cifs_sb->local_nls,
+                                        cifs_sb->mnt_cifs_flags &
+                                                CIFS_MOUNT_MAP_SPECIAL_CHR);
+
+        if ((rc != 0) && (tcon->ses->capabilities & CAP_UNIX))
+                rc = CIFSSMBUnixQuerySymLink(xid, tcon, full_path, &target_path,
+                                             cifs_sb->local_nls);
+
         kfree(full_path);
 out:
         if (rc != 0) {
@@ -459,7 +473,12 @@ cifs_symlink(struct inode *inode, struct dentry *direntry, const char *symname)
         cFYI(1, "symname is %s", symname);
 
         /* BB what if DFS and this volume is on different share? BB */
-        if (pTcon->unix_ext)
+        if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS)
+                rc = CIFSCreateMFSymLink(xid, pTcon, full_path, symname,
+                                         cifs_sb->local_nls,
+                                         cifs_sb->mnt_cifs_flags &
+                                                CIFS_MOUNT_MAP_SPECIAL_CHR);
+        else if (pTcon->unix_ext)
                 rc = CIFSUnixCreateSymLink(xid, pTcon, full_path, symname,
                                            cifs_sb->local_nls);
         /* else
diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
index d5e591fab475..6a8b417babab 100644
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -738,6 +738,15 @@ static int cifs_filldir(char *pfindEntry, struct file *file, filldir_t filldir,
                 cifs_autodisable_serverino(cifs_sb);
         }
 
+        if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS) &&
+            CIFSCouldBeMFSymlink(&fattr))
+                /*
+                 * trying to get the type and mode can be slow,
+                 * so just call those regular files for now, and mark
+                 * for reval
+                 */
+                fattr.cf_flags |= CIFS_FATTR_NEED_REVAL;
+
         ino = cifs_uniqueid_to_ino_t(fattr.cf_uniqueid);
         tmp_dentry = cifs_readdir_lookup(file->f_dentry, &qstring, &fattr);