From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx162.postini.com [74.125.245.162]) by kanga.kvack.org (Postfix) with SMTP id 51A8A6B0071 for ; Tue, 27 Nov 2012 20:15:52 -0500 (EST) Date: Tue, 27 Nov 2012 17:15:44 -0800 From: Andrew Morton Subject: Re: [PATCH] mm: fix balloon_page_movable() page->flags check Message-Id: <20121127171544.8bbb702a.akpm@linux-foundation.org> In-Reply-To: <20121128003409.GB7401@t510.redhat.com> References: <20121127145708.c7173d0d.akpm@linux-foundation.org> <1ccb1c95a52185bcc6009761cb2829197e2737ea.1354058194.git.aquini@redhat.com> <20121127155201.ddfea7e1.akpm@linux-foundation.org> <20121128003409.GB7401@t510.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Rafael Aquini Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sasha Levin , Mel Gorman , Rik van Riel On Tue, 27 Nov 2012 22:34:10 -0200 Rafael Aquini wrote: > Do you want me to resubmit this patch with the changes you suggested? oh, I think I can reach that far. How's this look? From: Andrew Morton Subject: mm-introduce-a-common-interface-for-balloon-pages-mobility-mm-fix-balloon_page_movable-page-flags-check-fix use PAGE_FLAGS_CHECK_AT_PREP, s/__balloon_page_flags/page_flags_cleared/, small cleanups Cc: "Michael S. Tsirkin" Cc: Andi Kleen Cc: Konrad Rzeszutek Wilk Cc: Mel Gorman Cc: Minchan Kim Cc: Rafael Aquini Cc: Rik van Riel Cc: Rusty Russell Cc: Sasha Levin Signed-off-by: Andrew Morton --- include/linux/balloon_compaction.h | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-) diff -puN include/linux/balloon_compaction.h~mm-introduce-a-common-interface-for-balloon-pages-mobility-mm-fix-balloon_page_movable-page-flags-check-fix include/linux/balloon_compaction.h --- a/include/linux/balloon_compaction.h~mm-introduce-a-common-interface-for-balloon-pages-mobility-mm-fix-balloon_page_movable-page-flags-check-fix +++ a/include/linux/balloon_compaction.h @@ -41,6 +41,7 @@ #ifndef _LINUX_BALLOON_COMPACTION_H #define _LINUX_BALLOON_COMPACTION_H #include +#include #include #include #include @@ -109,18 +110,16 @@ static inline void balloon_mapping_free( /* * __balloon_page_flags - helper to perform balloon @page ->flags tests. * - * As balloon pages are got from Buddy, and we do not play with page->flags + * As balloon pages are obtained from buddy and we do not play with page->flags * at driver level (exception made when we get the page lock for compaction), - * therefore we can safely identify a ballooned page by checking if the - * NR_PAGEFLAGS rightmost bits from the page->flags are all cleared. - * This approach also helps on skipping ballooned pages that are locked for - * compaction or release, thus mitigating their racy check at - * balloon_page_movable() + * we can safely identify a ballooned page by checking if the + * PAGE_FLAGS_CHECK_AT_PREP page->flags are all cleared. This approach also + * helps us skip ballooned pages that are locked for compaction or release, thus + * mitigating their racy check at balloon_page_movable() */ -#define BALLOON_PAGE_FLAGS_MASK ((1UL << NR_PAGEFLAGS) - 1) -static inline bool __balloon_page_flags(struct page *page) +static inline bool page_flags_cleared(struct page *page) { - return page->flags & BALLOON_PAGE_FLAGS_MASK ? false : true; + return !(page->flags & PAGE_FLAGS_CHECK_AT_PREP); } /* @@ -149,10 +148,10 @@ static inline bool __is_movable_balloon_ static inline bool balloon_page_movable(struct page *page) { /* - * Before dereferencing and testing mapping->flags, lets make sure + * Before dereferencing and testing mapping->flags, let's make sure * this is not a page that uses ->mapping in a different way */ - if (__balloon_page_flags(page) && !page_mapped(page) && + if (page_flags_cleared(page) && !page_mapped(page) && page_count(page) == 1) return __is_movable_balloon_page(page); _ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org