On Thu, Feb 27, 2025 at 10:59 PM Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> > +static struct page *anon_pipe_get_page(struct pipe_inode_info *pipe)
> > +{
> > + struct page *page;
> > +
> > + if (pipe->tmp_page[0]) {
> > + page = pipe->tmp_page[0];
> > + pipe->tmp_page[0] = NULL;
> > + } else if (pipe->tmp_page[1]) {
> > + page = pipe->tmp_page[1];
> > + pipe->tmp_page[1] = NULL;
> > + } else {
> > + page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
> > + }
> > +
> > + return page;
> > +}
>
> Perhaps something like
>
> for (i = 0; i < ARRAY_SIZE(pipe->tmp_page); i++) {
> if (pipe->tmp_page[i]) {
> struct page *page = pipe->tmp_page[i];
> pipe->tmp_page[i] = NULL;
> return page;
> }
> }
>
> return alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
> ?
>
> Same for anon_pipe_put_page() and free_pipe_info().
>
> This avoids the code duplication and allows to change the size of
> pipe->tmp_page[] array without other changes.
>
I have almost no opinion one way or the other and I'm not going to
argue about this bit. I only note I don't expect there is a legit
reason to go beyond 2 pages here. As in if more is warranted, the
approach to baking the area should probably change.
I started with this being spelled out so that I have easier time
toggling the extra slot for testing.
That said, I don't know who counts as the pipe man today. I can do the
needful(tm) no problem.
--
Mateusz Guzik <mjguzik gmail.com>
