Re: [linus:master] BUILD REGRESSION f3b5ad89de16f5d42e8ad36fbdf85f705c1ae051

[Linus Torvalds]

Nico,

On Sat, Dec 16, 2017 at 7:00 PM, kbuild test robot
<fengguang.wu@xxxxxxxxx> wrote:
>
> fs/cramfs/inode.c:641: undefined reference to `mtd_point'
> fs/cramfs/inode.c:658: undefined reference to `mtd_unpoint'
> fs/cramfs/inode.c:959: undefined reference to `mount_mtd'

This does seem to be real.

As of 99c18ce580c6 ("cramfs: direct memory access support") cramfs
seems to require MTD, but that's not expressed in the Kconfig.

Oddly, _some_ of the mtd functions are protected with

    if (IS_ENABLED(CCONFIG_CRAMFS_MTD) ..)

but cramfs_mtd_fill_super() is not.

It is only *used* if CONFIG_CRAMFS_MTD is enabled (the call to
mount_mtd(.., cramfs_mtd_fill_super) is conditional, but..

           Linus