the nul-terminated string helper desk chair rearrangement

[Christoph Hellwig]

On Wed, Oct 18, 2023 at 11:01:54PM -0700, Kees Cook wrote:
> Almost all of the remaining strncpy() usage is just string to string
> copying, but the corner cases that are being spun out that aren't
> strscpy() or strscpy_pad() are covered by strtomem(), kmemdup_nul(),
> and memcpy(). Each of these are a clear improvement since they remove
> the ambiguity of the intended behavior. Using seq_buf ends up being way
> more overhead than is needed.

I'm really not sure strscpy is much of an improvement.  In this particular
case in most other places we simply use a snprintf for nqns, which seems
useful here to if we don't want the full buf.

But switching to a completely undocumented helper like strscpy seems not
useful at all.