Re: [PATCH] tmpfs: Disallow CONFIG_TMPFS_INODE64 on s390

[Chris Down]

Andrew Morton writes:
> Currently there is an assumption in tmpfs that 64-bit architectures also
> have a 64-bit ino_t.  This is not true on s390 which has a 32-bit ino_t.
> With CONFIG_TMPFS_INODE64=y tmpfs mounts will get 64-bit inode numbers and
> display "inode64" in the mount options, but passing the "inode64" mount
> option will fail.  This leads to the following behavior:
>
> # mkdir mnt
> # mount -t tmpfs nodev mnt
> # mount -o remount,rw mnt
> mount: /home/ubuntu/mnt: mount point not mounted or bad option.
>
> As mount sees "inode64" in the mount options and thus passes it in the
> options for the remount.
>
>
> So prevent CONFIG_TMPFS_INODE64 from being selected on s390.
>
> Link: https://lkml.kernel.org/r/20210205230620.518245-1-seth.forshee@xxxxxxxxxxxxx
> Fixes: ea3271f7196c ("tmpfs: support 64-bit inums per-sb")
> Signed-off-by: Seth Forshee <seth.forshee@xxxxxxxxxxxxx>
> Cc: Chris Down <chris@xxxxxxxxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: Amir Goldstein <amir73il@xxxxxxxxx>
> Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
> Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>	[5.9+]
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>

Either of the two ways presented looks fine to me, no real preference. Thanks!

Acked-by: Chris Down <chris@xxxxxxxxxxxxxx>

> ---
>
> fs/Kconfig |    2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/fs/Kconfig~tmpfs-disallow-config_tmpfs_inode64-on-s390
> +++ a/fs/Kconfig
> @@ -203,7 +203,7 @@ config TMPFS_XATTR
>
> config TMPFS_INODE64
> 	bool "Use 64-bit ino_t by default in tmpfs"
> -	depends on TMPFS && 64BIT
> +	depends on TMPFS && 64BIT && !S390
> 	default n
> 	help
> 	  tmpfs has historically used only inode numbers as wide as an unsigned
> _