Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756286AbYFVTGP (ORCPT ); Sun, 22 Jun 2008 15:06:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756019AbYFVTEt (ORCPT ); Sun, 22 Jun 2008 15:04:49 -0400 Received: from ns1.suse.de ([195.135.220.2]:43534 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756008AbYFVTEs (ORCPT ); Sun, 22 Jun 2008 15:04:48 -0400 Date: Sun, 22 Jun 2008 12:01:40 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: Justin Forbes , Zwane Mwaikambo , "Theodore Ts'o" , Randy Dunlap , Dave Jones , Chuck Wolber , Chris Wedgwood , Michael Krufky , Chuck Ebbert , Domenico Andreoli , Willy Tarreau , Rodrigo Rubira Branco , torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Oleg Nesterov , Nick Piggin , KAMEZAWA Hiroyuki , Hugh Dickins , Ingo Molnar , Roland McGrath Subject: [patch 2/5] Reinstate ZERO_PAGE optimization in get_user_pages() and fix XIP Message-ID: <20080622190140.GD20141@suse.de> References: <20080622185327.348377223@mini.kroah.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline; filename="reinstate-zero_page-optimization-in-get_user_pages-and-fix-xip.patch" In-Reply-To: <20080622190111.GA20141@suse.de> User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4558 Lines: 145 2.6.25-stable review patch. If anyone has any objections, please let us know. ------------------ From: Linus Torvalds commit 89f5b7da2a6bad2e84670422ab8192382a5aeb9f upstream KAMEZAWA Hiroyuki and Oleg Nesterov point out that since the commit 557ed1fa2620dc119adb86b34c614e152a629a80 ("remove ZERO_PAGE") removed the ZERO_PAGE from the VM mappings, any users of get_user_pages() will generally now populate the VM with real empty pages needlessly. We used to get the ZERO_PAGE when we did the "handle_mm_fault()", but since fault handling no longer uses ZERO_PAGE for new anonymous pages, we now need to handle that special case in follow_page() instead. In particular, the removal of ZERO_PAGE effectively removed the core file writing optimization where we would skip writing pages that had not been populated at all, and increased memory pressure a lot by allocating all those useless newly zeroed pages. This reinstates the optimization by making the unmapped PTE case the same as for a non-existent page table, which already did this correctly. While at it, this also fixes the XIP case for follow_page(), where the caller could not differentiate between the case of a page that simply could not be used (because it had no "struct page" associated with it) and a page that just wasn't mapped. We do that by simply returning an error pointer for pages that could not be turned into a "struct page *". The error is arbitrarily picked to be EFAULT, since that was what get_user_pages() already used for the equivalent IO-mapped page case. [ Also removed an impossible test for pte_offset_map_lock() failing: that's not how that function works ] Acked-by: Oleg Nesterov Acked-by: Nick Piggin Cc: KAMEZAWA Hiroyuki Cc: Hugh Dickins Cc: Andrew Morton Cc: Ingo Molnar Cc: Roland McGrath Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/vdso.c | 2 +- mm/memory.c | 17 +++++++++++++---- mm/migrate.c | 10 ++++++++++ 3 files changed, 24 insertions(+), 5 deletions(-) --- a/arch/powerpc/kernel/vdso.c +++ b/arch/powerpc/kernel/vdso.c @@ -141,7 +141,7 @@ static void dump_one_vdso_page(struct pa printk("kpg: %p (c:%d,f:%08lx)", __va(page_to_pfn(pg) << PAGE_SHIFT), page_count(pg), pg->flags); - if (upg/* && pg != upg*/) { + if (upg && !IS_ERR(upg) /* && pg != upg*/) { printk(" upg: %p (c:%d,f:%08lx)", __va(page_to_pfn(upg) << PAGE_SHIFT), page_count(upg), --- a/mm/memory.c +++ b/mm/memory.c @@ -943,17 +943,15 @@ struct page *follow_page(struct vm_area_ } ptep = pte_offset_map_lock(mm, pmd, address, &ptl); - if (!ptep) - goto out; pte = *ptep; if (!pte_present(pte)) - goto unlock; + goto no_page; if ((flags & FOLL_WRITE) && !pte_write(pte)) goto unlock; page = vm_normal_page(vma, address, pte); if (unlikely(!page)) - goto unlock; + goto bad_page; if (flags & FOLL_GET) get_page(page); @@ -968,6 +966,15 @@ unlock: out: return page; +bad_page: + pte_unmap_unlock(ptep, ptl); + return ERR_PTR(-EFAULT); + +no_page: + pte_unmap_unlock(ptep, ptl); + if (!pte_none(pte)) + return page; + /* Fall through to ZERO_PAGE handling */ no_page_table: /* * When core dumping an enormous anonymous area that nobody @@ -1104,6 +1111,8 @@ int get_user_pages(struct task_struct *t cond_resched(); } + if (IS_ERR(page)) + return i ? i : PTR_ERR(page); if (pages) { pages[i] = page; --- a/mm/migrate.c +++ b/mm/migrate.c @@ -858,6 +858,11 @@ static int do_move_pages(struct mm_struc goto set_status; page = follow_page(vma, pp->addr, FOLL_GET); + + err = PTR_ERR(page); + if (IS_ERR(page)) + goto set_status; + err = -ENOENT; if (!page) goto set_status; @@ -921,6 +926,11 @@ static int do_pages_stat(struct mm_struc goto set_status; page = follow_page(vma, pm->addr, 0); + + err = PTR_ERR(page); + if (IS_ERR(page)) + goto set_status; + err = -ENOENT; /* Use PageReserved to check for zero page */ if (!page || PageReserved(page)) -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/