Re: [PATCH] xfs: add CONFIG_MMU dependency

Jan Kara
2024-09-09T13:42:21Z

On Mon 09-09-24 11:19:00, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> XFS no longer builds on kernels with MMU disabled:
>
> arm-linux-gnueabi-ld: fs/xfs/xfs_file.o: in function `xfs_write_fault.constprop.0':
> xfs_file.c:(.text.xfs_write_fault.constprop.0+0xc): undefined reference to `filemap_fsnotify_fault'
>
> It's rather unlikely that anyone is using this combination,
> so just add a Kconfig dependency.
>
> Fixes: 436df5326f57 ("xfs: add pre-content fsnotify hook for write faults")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Thanks! I've noticed the error from 0-day over the weekend as well. At this
point I'd rather handle this in a similar way as e.g. filemap_fault() is
handled in NOMMU case. I agree users of XFS (or bcachefs for that matter)
with !CONFIG_MMU are unlikely but fsnotify_filemap_fault() can grow more
users over time and providing the stub is easy enough. I'll push out fixed
version of the patch.

Honza

> ---
> fs/xfs/Kconfig | 1 +
> lib/Kconfig.debug | 1 +
> 2 files changed, 2 insertions(+)
>
> diff --git a/fs/xfs/Kconfig b/fs/xfs/Kconfig
> index fffd6fffdce0..1834932a512d 100644
> --- a/fs/xfs/Kconfig
> +++ b/fs/xfs/Kconfig
> @@ -2,6 +2,7 @@
> config XFS_FS
> tristate "XFS filesystem support"
> depends on BLOCK
> + depends on MMU
> select EXPORTFS
> select LIBCRC32C
> select FS_IOMAP
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 7c0546480078..8906e2cd1ed5 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -2862,6 +2862,7 @@ config TEST_KMOD
> depends on NETDEVICES && NET_CORE && INET # for TUN
> depends on BLOCK
> depends on PAGE_SIZE_LESS_THAN_256KB # for BTRFS
> + depends on MMU # for XFS_FS
> select TEST_LKM
> select XFS_FS
> select TUN
> --
> 2.39.2
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR