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Re: [PATCH v2] x86: fix small LDT allocation for Xen

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* Jan Beulich <JBeulich@suse.com> wrote:

> >> @@ -95,7 +95,7 @@ static void free_ldt_struct(struct ldt_s
> >>         if (ldt->size * LDT_ENTRY_SIZE > PAGE_SIZE)
> >>                 vfree(ldt->entries);
> >>         else
> >> -               kfree(ldt->entries);
> >> +               put_page(virt_to_page(ldt->entries));
> > 
> > FWIW, I'm not convinced this is or was correct.  Using free_page looks
> > a bit safer, and free_page does more than just put_page.
> 
> Actually I agree. put_page() is meant to be paired with get_page();
> __get_free_pages() is just misleading (i.e. doesn't imply a get_page())
> and instead is to be paired with free_pages(). Will do a v3 then.

So put_page() is a page cache primitive and should not be used outside of it.

As it happens, it is safe to put_page() a regularly allocated page as well, but 
it's a little bit slower than doing a free_page().

Thanks,

	Ingo
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[PATCH v2] x86: fix small LDT allocation for Xen "Jan Beulich" <JBeulich@suse.com> - 2015-09-02 14:50 +0200
  Re: [PATCH v2] x86: fix small LDT allocation for Xen Andy Lutomirski <luto@amacapital.net> - 2015-09-02 16:10 +0200
    Re: [PATCH v2] x86: fix small LDT allocation for Xen "Jan Beulich" <JBeulich@suse.com> - 2015-09-02 17:50 +0200
      Re: [PATCH v2] x86: fix small LDT allocation for Xen Ingo Molnar <mingo@kernel.org> - 2015-09-02 19:00 +0200

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