From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f182.google.com (mail-wi0-f182.google.com [209.85.212.182]) by kanga.kvack.org (Postfix) with ESMTP id 990BF6B00DE for ; Tue, 6 Jan 2015 12:43:52 -0500 (EST) Received: by mail-wi0-f182.google.com with SMTP id h11so5850115wiw.9 for ; Tue, 06 Jan 2015 09:43:52 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id a5si25832302wix.30.2015.01.06.09.43.51 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 06 Jan 2015 09:43:51 -0800 (PST) Message-ID: <54AC1ED5.2050101@suse.cz> Date: Tue, 06 Jan 2015 18:43:49 +0100 From: Vlastimil Babka MIME-Version: 1.0 Subject: Re: [PATCH] mm/page_alloc.c: drop dead destroy_compound_page() References: <1420458382-161038-1-git-send-email-kirill.shutemov@linux.intel.com> In-Reply-To: <1420458382-161038-1-git-send-email-kirill.shutemov@linux.intel.com> Content-Type: text/plain; charset=iso-8859-2 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" , akpm@linux-foundation.org Cc: aarcange@redhat.com, linux-mm@kvack.org On 01/05/2015 12:46 PM, Kirill A. Shutemov wrote: > The only caller is __free_one_page(). By the time we should have > page->flags to be cleared already: > > - for 0-order pages though PCP list: Can there even be a 0-order compound page? I guess not, so this is just confusing? Otherwise it seems like you are right and it's a dead code to be removed. I tried to check history to see when it was actually needed, but seems it predates git. Acked-by: Vlastimil Babka > free_hot_cold_page() > free_pages_prepare() > free_pages_check() > page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; > > > free_pcppages_bulk() > page = > __free_one_page(page) > > - for non-0-order pages: > __free_pages_ok() > free_pages_prepare() > free_pages_check() > page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; > free_one_page() > __free_one_page() > > So there's no way PageCompound() will return true in __free_one_page(). > Let's remove dead destroy_compound_page() and put assert for page->flags > there instead. > > Signed-off-by: Kirill A. Shutemov > --- > mm/page_alloc.c | 35 +---------------------------------- > 1 file changed, 1 insertion(+), 34 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 1bb65e6f48dd..5e75380dacab 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -381,36 +381,6 @@ void prep_compound_page(struct page *page, unsigned long order) > } > } > > -/* update __split_huge_page_refcount if you change this function */ > -static int destroy_compound_page(struct page *page, unsigned long order) > -{ > - int i; > - int nr_pages = 1 << order; > - int bad = 0; > - > - if (unlikely(compound_order(page) != order)) { > - bad_page(page, "wrong compound order", 0); > - bad++; > - } > - > - __ClearPageHead(page); > - > - for (i = 1; i < nr_pages; i++) { > - struct page *p = page + i; > - > - if (unlikely(!PageTail(p))) { > - bad_page(page, "PageTail not set", 0); > - bad++; > - } else if (unlikely(p->first_page != page)) { > - bad_page(page, "first_page not consistent", 0); > - bad++; > - } > - __ClearPageTail(p); > - } > - > - return bad; > -} > - > static inline void prep_zero_page(struct page *page, unsigned int order, > gfp_t gfp_flags) > { > @@ -613,10 +583,7 @@ static inline void __free_one_page(struct page *page, > int max_order = MAX_ORDER; > > VM_BUG_ON(!zone_is_initialized(zone)); > - > - if (unlikely(PageCompound(page))) > - if (unlikely(destroy_compound_page(page, order))) > - return; > + VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page); > > VM_BUG_ON(migratetype == -1); > if (is_migrate_isolate(migratetype)) { > -- 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