Re: [PATCH v3] fs: Replace user_access_{begin/end} by scoped user access

[Christophe Leroy (CS GROUP)]

Le 16/03/2026 à 18:12, Linus Torvalds a écrit :
> On Mon, 16 Mar 2026 at 01:53, Christophe Leroy (CS GROUP)
> <chleroy@xxxxxxxxxx> wrote:
> > -       if (!user_write_access_begin(dirent,
> > -                       (unsigned long)(dirent->d_name + namlen + 1) -
> > -                               (unsigned long)dirent))
> > -               goto efault;
>
> This was already pretty unreadable (my bad), but..
>
> > +       scoped_user_write_access_size(dirent, (unsigned long)(dirent->d_name + namlen + 1) -
> > +                                             (unsigned long)dirent, efault) {
>
> .. in my opinion, this is even worse. It's a 90+ character long line
> (or something), *and* it continues on the next line.
>
> Yes, yes, the old code was disgusting too, but when changing it for
> something that is supposed to be easier to read, please let's make it
> *really* easier to read.
>
> (And yes, there's another case of this same pattern a bit later).

The other pattern looks similar but is not exactly the same.

> Adding a helper inline function like dirent_size() might do it. And I
> think it might as well be cleaned up while at it, and make it be
> something like
>
>      static inline size_t dirent_size(int namelen)
>      {
>          return offsetof(struct linux_dirent, d_name) + namelen + 1;
>      }

...

> Hmm? Can you do at least that dirent_size() kind of cleanup?

Thanks for the suggestion.

I went for a local var alternative, see v4. A helper would be of no help 
as the two patterns are not exactly the same:

	size_t size = offsetof(struct old_linux_dirent, d_name) + namlen + 1;

	size_t size = offsetof(struct compat_old_linux_dirent, d_name) + namlen 
+ 1;


Christophe