Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> writes:
> On Tue, May 18, 2021 at 5:17 PM Linus Torvalds
> <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>>
>> This looks sensible to me (and numbers talk!), but as Rik says, it
>> would probably be a good idea to move the trylock_page()/unlock_page()
>> into try_to_free_idle_swapcache(), and that would make the calling
>> side a whole lot cleaner and easier to read.
>
> To keep the error handling simple, and keep that "if that didn't work,
> just return" logic in you had, doing it as two functions like:
>
> static inline void locked_try_to_free_idle_swapcache(struct page *page)
> { .. your current try_to_free_idle_swapcache() .. }
>
> void try_to_free_idle_swapcache(struct page *page)
> {
> if (trylock_page(page)) {
> locked_try_to_free_idle_swapcache(page);
> unlock_page(page);
> }
> }
>
> would keep that readability and simplicity.
>
> And then the wp_page_copy() code ends up being
>
> if (page_copied && PageSwapCache(old_page) && !page_mapped(old_page))
> try_to_free_idle_swapcache(old_page);
>
> which looks pretty sensible to me: if we copied the page, and the old
> page is a no longer mapped swap cache page, let's try to free it.
>
> That's still a hell of a long conditional, partly because of those
> long names. But at least it's conceptually fairly straightforward and
> easy to understand what's going on.
Thanks! That looks much better. I will do that in the next version.
Best Regards,
Huang, Ying
