fs: return EPERM on immutable inode

In most cases, EPERM is returned on immutable inode, and there're only a
few places returning EACCES. I noticed this when running LTP on
overlayfs, setxattr03 failed due to unexpected EACCES on immutable
inode.

So converting all EACCES to EPERM on immutable inode.

Acked-by: Dave Chinner <[e-mail]>
Signed-off-by: Eryu Guan <[e-mail]>
Signed-off-by: Al Viro <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/gfs2/inode.c

···
 	}
 
 	if ((mask & MAY_WRITE) && IS_IMMUTABLE(inode))
-		error = -EACCES;
+		error = -EPERM;
 	else
 		error = generic_permission(inode, mask);
 	if (gfs2_holder_initialized(&i_gh))

fs/namei.c

···
 		 * Nobody gets write access to an immutable file.
 		 */
 		if (IS_IMMUTABLE(inode))
-			return -EACCES;
+			return -EPERM;
 
 		/*
 		 * Updating mtime will likely cause i_uid and i_gid to be

fs/utimes.c

···
 		 * then we need to check permissions, because
 		 * inode_change_ok() won't do it.
 		 */
-		error = -EACCES;
+		error = -EPERM;
                 if (IS_IMMUTABLE(inode))
 			goto mnt_drop_write_and_out;
 
+		error = -EACCES;
 		if (!inode_owner_or_capable(inode)) {
 			error = inode_permission(inode, MAY_WRITE);
 			if (error)

fs/xfs/xfs_ioctl.c

···
 	}
 
 	if ((fmode & FMODE_WRITE) && IS_IMMUTABLE(inode)) {
-		error = -EACCES;
+		error = -EPERM;
 		goto out_dput;
 	}