From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753769AbZEHHbQ (ORCPT ); Fri, 8 May 2009 03:31:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752805AbZEHHa6 (ORCPT ); Fri, 8 May 2009 03:30:58 -0400 Received: from rv-out-0506.google.com ([209.85.198.226]:6797 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752592AbZEHHa5 (ORCPT ); Fri, 8 May 2009 03:30:57 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:in-reply-to:references:x-mailer :mime-version:content-type:content-transfer-encoding; b=pcWyRfIdjtA88DuMQsyP6m7ojiCGoer70X3CptZkAyYzYmYhaJyCakWY64Uyybv8Ya wZGKqBayFEvGMeYrxTa8zhiuxJoK508+aZ7gi/3DSqr4CUXoBm9+WmNAi/SVOvh2BskT ocEMxNE76+kIBWh2LaErb9PZIPHE0mUCYsggA= Date: Fri, 8 May 2009 16:30:42 +0900 From: Minchan Kim To: Wu Fengguang Cc: Johannes Weiner , Andrew Morton , Peter Zijlstra , Rik van Riel , "linux-kernel@vger.kernel.org" , "tytso@mit.edu" , "linux-mm@kvack.org" , Elladan , Nick Piggin , Christoph Lameter , KOSAKI Motohiro Subject: Re: [PATCH -mm] vmscan: make mapped executable pages the first class citizen Message-Id: <20090508163042.ba4ef116.minchan.kim@barrios-desktop> In-Reply-To: <20090508030209.GA8892@localhost> References: <20090430205936.0f8b29fc@riellaptop.surriel.com> <20090430181340.6f07421d.akpm@linux-foundation.org> <20090430215034.4748e615@riellaptop.surriel.com> <20090430195439.e02edc26.akpm@linux-foundation.org> <49FB01C1.6050204@redhat.com> <20090501123541.7983a8ae.akpm@linux-foundation.org> <20090503031539.GC5702@localhost> <1241432635.7620.4732.camel@twins> <20090507121101.GB20934@localhost> <20090507151039.GA2413@cmpxchg.org> <20090508030209.GA8892@localhost> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.9; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Let me have a question. On Fri, 8 May 2009 11:02:09 +0800 Wu Fengguang wrote: > On Thu, May 07, 2009 at 11:10:39PM +0800, Johannes Weiner wrote: > > On Thu, May 07, 2009 at 08:11:01PM +0800, Wu Fengguang wrote: > > > Introduce AS_EXEC to mark executables and their linked libraries, and to > > > protect their referenced active pages from being deactivated. > > > > > > CC: Elladan > > > CC: Nick Piggin > > > CC: Johannes Weiner > > > CC: Christoph Lameter > > > CC: KOSAKI Motohiro > > > Acked-by: Peter Zijlstra > > > Acked-by: Rik van Riel > > > Signed-off-by: Wu Fengguang > > > --- > > > include/linux/pagemap.h | 1 + > > > mm/mmap.c | 2 ++ > > > mm/nommu.c | 2 ++ > > > mm/vmscan.c | 35 +++++++++++++++++++++++++++++++++-- > > > 4 files changed, 38 insertions(+), 2 deletions(-) > > > > > > --- linux.orig/include/linux/pagemap.h > > > +++ linux/include/linux/pagemap.h > > > @@ -25,6 +25,7 @@ enum mapping_flags { > > > #ifdef CONFIG_UNEVICTABLE_LRU > > > AS_UNEVICTABLE = __GFP_BITS_SHIFT + 3, /* e.g., ramdisk, SHM_LOCK */ > > > #endif > > > + AS_EXEC = __GFP_BITS_SHIFT + 4, /* mapped PROT_EXEC somewhere */ > > > }; > > > > > > static inline void mapping_set_error(struct address_space *mapping, int error) > > > --- linux.orig/mm/mmap.c > > > +++ linux/mm/mmap.c > > > @@ -1194,6 +1194,8 @@ munmap_back: > > > goto unmap_and_free_vma; > > > if (vm_flags & VM_EXECUTABLE) > > > added_exe_file_vma(mm); > > > + if (vm_flags & VM_EXEC) > > > + set_bit(AS_EXEC, &file->f_mapping->flags); > > > } else if (vm_flags & VM_SHARED) { > > > error = shmem_zero_setup(vma); > > > if (error) > > > --- linux.orig/mm/nommu.c > > > +++ linux/mm/nommu.c > > > @@ -1224,6 +1224,8 @@ unsigned long do_mmap_pgoff(struct file > > > added_exe_file_vma(current->mm); > > > vma->vm_mm = current->mm; > > > } > > > + if (vm_flags & VM_EXEC) > > > + set_bit(AS_EXEC, &file->f_mapping->flags); > > > } > > > > I find it a bit ugly that it applies an attribute of the memory area > > (per mm) to the page cache mapping (shared). Because this in turn > > means that the reference through a non-executable vma might get the > > pages rotated just because there is/was an executable mmap around. > > Right, the intention was to identify a whole executable/library file, > eg. /bin/bash or /lib/libc-2.9.so, covering both _text_ and _data_ > sections. But, your patch is care just text section. Do I miss something ? > > > down_write(&nommu_region_sem); > > > --- linux.orig/mm/vmscan.c > > > +++ linux/mm/vmscan.c > > > @@ -1230,6 +1230,7 @@ static void shrink_active_list(unsigned > > > unsigned long pgmoved; > > > unsigned long pgscanned; > > > LIST_HEAD(l_hold); /* The pages which were snipped off */ > > > + LIST_HEAD(l_active); > > > LIST_HEAD(l_inactive); > > > struct page *page; > > > struct pagevec pvec; > > > @@ -1269,8 +1270,15 @@ static void shrink_active_list(unsigned > > > > > > /* page_referenced clears PageReferenced */ > > > if (page_mapping_inuse(page) && > > > - page_referenced(page, 0, sc->mem_cgroup)) > > > + page_referenced(page, 0, sc->mem_cgroup)) { > > > + struct address_space *mapping = page_mapping(page); > > > + > > > pgmoved++; > > > + if (mapping && test_bit(AS_EXEC, &mapping->flags)) { > > > + list_add(&page->lru, &l_active); > > > + continue; > > > + } > > > + } > > > > Since we walk the VMAs in page_referenced anyway, wouldn't it be > > better to check if one of them is executable? This would even work > > for executable anon pages. After all, there are applications that cow > > executable mappings (sbcl and other language environments that use an > > executable, run-time modified core image come to mind). > > The page_referenced() path will only cover the _text_ section. But Why did you said that "The page_referenced() path will only cover the ""_text_"" section" ? Could you elaborate please ? > yeah, the _data_ section is more likely to grow huge in some rare cases. > > Thanks, > Fengguang > > -- > 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 -- Kinds Regards Minchan Kim