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    SubjectRe: [PATCH] mm: do not call bad_page on PG_reserved check
    On Sat, 18 Nov 2006, David Rientjes wrote:

    > The return value of free_pages_check() indicates if PG_reserved was set.
    > If so, the calling functions return immediately and no pages are freed so
    > there is no need to call bad_page().
    >
    > Cc: Andi Kleen <ak@suse.de>
    > Cc: Nick Piggin <npiggin@suse.de>
    > Signed-off-by: David Rientjes <rientjes@cs.washington.edu>

    NAK. You're missing the point. If an attempt is made to free a
    reserved page, it implies that the page reference counting has
    gone wrong: we want to hear about that (so call bad_page),
    and we dare not reuse the page (so skip freeing it).

    What might be a good change, is to avoid freeing a page which meets
    _any_ of the criteria for calling bad_page: I often wonder whether
    to do that, alongside abandoning that hopeless page_mapcount BUG in
    page_remove_rmap, which has almost(?) never helped lead us to any fix.

    Hugh

    > ---
    > mm/page_alloc.c | 1 -
    > 1 files changed, 0 insertions(+), 1 deletions(-)
    >
    > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
    > index bf2f6cf..99bc29d 100644
    > --- a/mm/page_alloc.c
    > +++ b/mm/page_alloc.c
    > @@ -439,7 +439,6 @@ static inline int free_pages_check(struc
    > 1 << PG_slab |
    > 1 << PG_swapcache |
    > 1 << PG_writeback |
    > - 1 << PG_reserved |
    > 1 << PG_buddy ))))
    > bad_page(page);
    > if (PageDirty(page))
    -
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