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>

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 */

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)

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

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);