Re: [PATCH 15/22] Do not disable interrupts in free_page_mlock()

Lee Schermerhorn
2009-04-24T11:52:29Z

On Fri, 2009-04-24 at 12:33 +0100, Mel Gorman wrote:
> On Fri, Apr 24, 2009 at 09:33:50AM +0900, KOSAKI Motohiro wrote:
> > > > @@ -157,14 +157,9 @@ static inline void mlock_migrate_page(struct page *newpage, struct page *page)
> > > > */
> > > > static inline void free_page_mlock(struct page *page)
> > > > {
> > > > - if (unlikely(TestClearPageMlocked(page))) {
> > > > - unsigned long flags;
> > > > -
> > > > - local_irq_save(flags);
> > > > - __dec_zone_page_state(page, NR_MLOCK);
> > > > - __count_vm_event(UNEVICTABLE_MLOCKFREED);
> > > > - local_irq_restore(flags);
> > > > - }
> > > > + __ClearPageMlocked(page);
> > > > + __dec_zone_page_state(page, NR_MLOCK);
> > > > + __count_vm_event(UNEVICTABLE_MLOCKFREED);
> > > > }
> > >
> > > The conscientuous reviewer runs around and checks for free_page_mlock()
> > > callers in other .c files which might be affected.
> > >
> > > Only there are no such callers.
> > >
> > > The reviewer's job would be reduced if free_page_mlock() wasn't
> > > needlessly placed in a header file!
> >
> > very sorry.
> >
> > How about this?
> >
> > =============================================
> > Subject: [PATCH] move free_page_mlock() to page_alloc.c
> >
> > Currently, free_page_mlock() is only called from page_alloc.c.
> > Thus, we can move it to page_alloc.c.
> >
>
> Looks good, but here is a version rebased on top of the patch series
> where it would be easier to merge with "Do not disable interrupts in
> free_page_mlock()".
>
> I do note why it might be in the header though - it keeps all the
> CONFIG_HAVE_MLOCKED_PAGE_BIT-related helper functions together making it
> easier to find them. Lee, was that the intention?

Yes. Having been dinged one too many times for adding extraneous
#ifdef's to .c's I try to avoid that...

Note that in page-flags.h, we define MLOCK_PAGES as 0 or 1 based on
CONFIG_HAVE_MLOCKED_PAGE_BIT, so you could test that in
free_page_mlock() to eliminate the #ifdef in page_alloc.c as we do in
try_to_unmap_*() over in rmap.c. Guess I could have done that when I
added MLOCK_PAGES. Got lost in the heat of the battle.

Lee

>
> =======
> From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>
> Move free_page_mlock() from mm/internal.h to mm/page_alloc.c
>
> Currently, free_page_mlock() is only called from page_alloc.c. This patch
> moves it from a header to to page_alloc.c.
>
> [mel@csn.ul.ie: Rebase on top of page allocator patches]
> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
> Cc: Christoph Lameter <cl@linux-foundation.org>
> Cc: Pekka Enberg <penberg@cs.helsinki.fi>
> Cc: Dave Hansen <dave@linux.vnet.ibm.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> ---
> mm/internal.h | 13 -------------
> mm/page_alloc.c | 16 ++++++++++++++++
> 2 files changed, 16 insertions(+), 13 deletions(-)
>
> diff --git a/mm/internal.h b/mm/internal.h
> index 58ec1bc..4b1672a 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -150,18 +150,6 @@ static inline void mlock_migrate_page(struct page *newpage, struct page *page)
> }
> }
>
> -/*
> - * free_page_mlock() -- clean up attempts to free and mlocked() page.
> - * Page should not be on lru, so no need to fix that up.
> - * free_pages_check() will verify...
> - */
> -static inline void free_page_mlock(struct page *page)
> -{
> - __ClearPageMlocked(page);
> - __dec_zone_page_state(page, NR_MLOCK);
> - __count_vm_event(UNEVICTABLE_MLOCKFREED);
> -}
> -
> #else /* CONFIG_HAVE_MLOCKED_PAGE_BIT */
> static inline int is_mlocked_vma(struct vm_area_struct *v, struct page *p)
> {
> @@ -170,7 +158,6 @@ static inline int is_mlocked_vma(struct vm_area_struct *v, struct page *p)
> static inline void clear_page_mlock(struct page *page) { }
> static inline void mlock_vma_page(struct page *page) { }
> static inline void mlock_migrate_page(struct page *new, struct page *old) { }
> -static inline void free_page_mlock(struct page *page) { }
>
> #endif /* CONFIG_HAVE_MLOCKED_PAGE_BIT */
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index f08b4cb..3db5f57 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -433,6 +433,22 @@ static inline int page_is_buddy(struct page *page, struct page *buddy,
> return 0;
> }
>
> +#ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
> +/*
> + * free_page_mlock() -- clean up attempts to free and mlocked() page.
> + * Page should not be on lru, so no need to fix that up.
> + * free_pages_check() will verify...
> + */
> +static inline void free_page_mlock(struct page *page)
> +{
> + __ClearPageMlocked(page);
> + __dec_zone_page_state(page, NR_MLOCK);
> + __count_vm_event(UNEVICTABLE_MLOCKFREED);
> +}
> +#else
> +static inline void free_page_mlock(struct page *page) { }
> +#endif /* CONFIG_HAVE_MLOCKED_PAGE_BIT */
> +
> /*
> * Freeing function for a buddy system allocator.
> *
>