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; /* -- 1.7.11.4 -- 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>