On Tue, Sep 25, 2012 at 1:05 PM, Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> wrote: > On Tue, Sep 25, 2012 at 11:59:51AM -0400, KOSAKI Motohiro wrote: >> On Tue, Sep 25, 2012 at 9:56 AM, Naoya Horiguchi >> <n-horiguchi@xxxxxxxxxxxxx> wrote: >> > KPF_THP can be set on non-huge compound pages like slab pages, because >> > PageTransCompound only sees PG_head and PG_tail. Obviously this is a bug >> > and breaks user space applications which look for thp via /proc/kpageflags. >> > Currently thp is constructed only on anonymous pages, so this patch makes >> > KPF_THP be set when both of PageAnon and PageTransCompound are true. >> >> Indeed. Please add some comment too. > > Sure. I send revised one. > > Thanks, > Naoya > --- > From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > Date: Mon, 24 Sep 2012 16:28:30 -0400 > Subject: [PATCH v2] pagemap: fix wrong KPF_THP on slab pages > > KPF_THP can be set on non-huge compound pages like slab pages, because > PageTransCompound only sees PG_head and PG_tail. Obviously this is a bug > and breaks user space applications which look for thp via /proc/kpageflags. > Currently thp is constructed only on anonymous pages, so this patch makes > KPF_THP be set when both of PageAnon and PageTransCompound are true. > > Changelog in v2: > - add a comment in code > > Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > --- > fs/proc/page.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/fs/proc/page.c b/fs/proc/page.c > index 7fcd0d6..f7cd2f6c 100644 > --- a/fs/proc/page.c > +++ b/fs/proc/page.c > @@ -115,7 +115,12 @@ u64 stable_page_flags(struct page *page) > u |= 1 << KPF_COMPOUND_TAIL; > if (PageHuge(page)) > u |= 1 << KPF_HUGE; > - else if (PageTransCompound(page)) > + /* > + * Since THP is relevant only for anonymous pages so far, we check it > + * explicitly with PageAnon. Otherwise thp is confounded with non-huge > + * compound pages like slab pages. > + */ > + else if (PageTransCompound(page) && PageAnon(page)) > u |= 1 << KPF_THP; Looks good to me. Acked-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>