CIFS: Implement follow_link for SMB2

that allows to access files through symlink created on a server.

Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>

1 files changed, 5 insertions, 19 deletions

diff --git a/fs/cifs/link.c b/fs/cifs/link.c
index 562044f700e5..7e36ceba0c7a 100644
--- a/fs/cifs/link.c
+++ b/fs/cifs/link.c
@@ -509,6 +509,7 @@ cifs_follow_link(struct dentry *direntry, struct nameidata *nd)
         struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
         struct tcon_link *tlink = NULL;
         struct cifs_tcon *tcon;
+        struct TCP_Server_Info *server;
 
         xid = get_xid();
 
@@ -519,25 +520,7 @@ cifs_follow_link(struct dentry *direntry, struct nameidata *nd)
                 goto out;
         }
         tcon = tlink_tcon(tlink);
-
-        /*
-         * For now, we just handle symlinks with unix extensions enabled.
-         * Eventually we should handle NTFS reparse points, and MacOS
-         * symlink support. For instance...
-         *
-         * rc = CIFSSMBQueryReparseLinkInfo(...)
-         *
-         * For now, just return -EACCES when the server doesn't support posix
-         * extensions. Note that we still allow querying symlinks when posix
-         * extensions are manually disabled. We could disable these as well
-         * but there doesn't seem to be any harm in allowing the client to
-         * read them.
-         */
-        if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS) &&
-            !cap_unix(tcon->ses)) {
-                rc = -EACCES;
-                goto out;
-        }
+        server = tcon->ses->server;
 
         full_path = build_path_from_dentry(direntry);
         if (!full_path)
@@ -559,6 +542,9 @@ cifs_follow_link(struct dentry *direntry, struct nameidata *nd)
         if ((rc != 0) && cap_unix(tcon->ses))
                 rc = CIFSSMBUnixQuerySymLink(xid, tcon, full_path, &target_path,
                                              cifs_sb->local_nls);
+        else if (rc != 0 && server->ops->query_symlink)
+                rc = server->ops->query_symlink(xid, tcon, full_path,
+                                                &target_path, cifs_sb);
 
         kfree(full_path);
 out: