Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932152AbbKBNC7 (ORCPT ); Mon, 2 Nov 2015 08:02:59 -0500 Received: from mail-wm0-f44.google.com ([74.125.82.44]:34402 "EHLO mail-wm0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753616AbbKBM5x (ORCPT ); Mon, 2 Nov 2015 07:57:53 -0500 Date: Mon, 2 Nov 2015 14:57:49 +0200 From: "Kirill A. Shutemov" To: Minchan Kim Cc: Hugh Dickins , Sasha Levin , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Rik van Riel , Mel Gorman , Michal Hocko , Johannes Weiner , Vlastimil Babka Subject: Re: kernel oops on mmotm-2015-10-15-15-20 Message-ID: <20151102125749.GB7473@node.shutemov.name> References: <20151021052836.GB6024@bbox> <20151021110723.GC10597@node.shutemov.name> <20151022000648.GD23631@bbox> <20151022012136.GG23631@bbox> <20151022090051.GH23631@bbox> <20151029002524.GA12018@node.shutemov.name> <20151029075829.GA16099@bbox> <20151029095206.GB29870@node.shutemov.name> <20151030070350.GB16099@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151030070350.GB16099@bbox> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10216 Lines: 248 On Fri, Oct 30, 2015 at 04:03:50PM +0900, Minchan Kim wrote: > On Thu, Oct 29, 2015 at 11:52:06AM +0200, Kirill A. Shutemov wrote: > > On Thu, Oct 29, 2015 at 04:58:29PM +0900, Minchan Kim wrote: > > > On Thu, Oct 29, 2015 at 02:25:24AM +0200, Kirill A. Shutemov wrote: > > > > On Thu, Oct 22, 2015 at 06:00:51PM +0900, Minchan Kim wrote: > > > > > On Thu, Oct 22, 2015 at 10:21:36AM +0900, Minchan Kim wrote: > > > > > > Hello Hugh, > > > > > > > > > > > > On Wed, Oct 21, 2015 at 05:59:59PM -0700, Hugh Dickins wrote: > > > > > > > On Thu, 22 Oct 2015, Minchan Kim wrote: > > > > > > > > > > > > > > > > I added the code to check it and queued it again but I had another oops > > > > > > > > in this time but symptom is related to anon_vma, too. > > > > > > > > (kernel is based on recent mmotm + unconditional mkdirty for bug fix) > > > > > > > > It seems page_get_anon_vma returns NULL since the page was not page_mapped > > > > > > > > at that time but second check of page_mapped right before try_to_unmap seems > > > > > > > > to be true. > > > > > > > > > > > > > > > > Adding 4191228k swap on /dev/vda5. Priority:-1 extents:1 across:4191228k FS > > > > > > > > Adding 4191228k swap on /dev/vda5. Priority:-1 extents:1 across:4191228k FS > > > > > > > > page:ffffea0001cfbfc0 count:3 mapcount:1 mapping:ffff88007f1b5f51 index:0x600000aff > > > > > > > > flags: 0x4000000000048019(locked|uptodate|dirty|swapcache|swapbacked) > > > > > > > > page dumped because: VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma) > > > > > > > > > > > > > > That's interesting, that's one I added in my page migration series. > > > > > > > Let me think on it, but it could well relate to the one you got before. > > > > > > > > > > > > I will roll back to mm/madv_free-v4.3-rc5-mmotm-2015-10-15-15-20 > > > > > > instead of next-20151021 to remove noise from your migration cleanup > > > > > > series and will test it again. > > > > > > If it is fixed, I will test again with your migration patchset, then. > > > > > > > > > > I tested mmotm-2015-10-15-15-20 with test program I attach for a long time. > > > > > Therefore, there is no patchset from Hugh's migration patch in there. > > > > > And I added below debug code with request from Kirill to all test kernels. > > > > > > > > It took too long time (and a lot of printk()), but I think I track it down > > > > finally. > > > > > > > > The patch below seems fixes issue for me. It's not yet properly tested, but > > > > looks like it works. > > > > > > > > The problem was my wrong assumption on how migration works: I thought that > > > > kernel would wait migration to finish on before deconstruction mapping. > > > > > > > > But turn out that's not true. > > > > > > > > As result if zap_pte_range() races with split_huge_page(), we can end up > > > > with page which is not mapped anymore but has _count and _mapcount > > > > elevated. The page is on LRU too. So it's still reachable by vmscan and by > > > > pfn scanners (Sasha showed few similar traces from compaction too). > > > > It's likely that page->mapping in this case would point to freed anon_vma. > > > > > > > > BOOM! > > > > > > > > The patch modify freeze/unfreeze_page() code to match normal migration > > > > entries logic: on setup we remove page from rmap and drop pin, on removing > > > > we get pin back and put page on rmap. This way even if migration entry > > > > will be removed under us we don't corrupt page's state. > > > > > > > > Please, test. > > > > > > > > > > kernel: On mmotm-2015-10-15-15-20 + pte_mkdirty patch + your new patch, I tested > > > one I sent to you(ie, oops.c + memcg_test.sh) > > > > > > page:ffffea00016a0000 count:3 mapcount:0 mapping:ffff88007f49d001 index:0x600001800 compound_mapcount: 0 > > > flags: 0x4000000000044009(locked|uptodate|head|swapbacked) > > > page dumped because: VM_BUG_ON_PAGE(!page_mapcount(page)) > > > page->mem_cgroup:ffff88007f613c00 > > > > Ignore my previous answer. Still sleeping. > > > > The right way to fix I think is something like: > > > > diff --git a/mm/rmap.c b/mm/rmap.c > > index 35643176bc15..f2d46792a554 100644 > > --- a/mm/rmap.c > > +++ b/mm/rmap.c > > @@ -1173,20 +1173,12 @@ void do_page_add_anon_rmap(struct page *page, > > bool compound = flags & RMAP_COMPOUND; > > bool first; > > > > - if (PageTransCompound(page)) { > > + if (PageTransCompound(page) && compound) { > > + atomic_t *mapcount; > > VM_BUG_ON_PAGE(!PageLocked(page), page); > > - if (compound) { > > - atomic_t *mapcount; > > - > > - VM_BUG_ON_PAGE(!PageTransHuge(page), page); > > - mapcount = compound_mapcount_ptr(page); > > - first = atomic_inc_and_test(mapcount); > > - } else { > > - /* Anon THP always mapped first with PMD */ > > - first = 0; > > - VM_BUG_ON_PAGE(!page_mapcount(page), page); > > - atomic_inc(&page->_mapcount); > > - } > > + VM_BUG_ON_PAGE(!PageTransHuge(page), page); > > + mapcount = compound_mapcount_ptr(page); > > + first = atomic_inc_and_test(mapcount); > > } else { > > VM_BUG_ON_PAGE(compound, page); > > first = atomic_inc_and_test(&page->_mapcount); > > -- > > kernel: On mmotm-2015-10-15-15-20 + pte_mkdirty patch + freeze/unfreeze patch + above patch, > > Adding 4191228k swap on /dev/vda5. Priority:-1 extents:1 across:4191228k FS > Adding 4191228k swap on /dev/vda5. Priority:-1 extents:1 across:4191228k FS > Adding 4191228k swap on /dev/vda5. Priority:-1 extents:1 across:4191228k FS > Adding 4191228k swap on /dev/vda5. Priority:-1 extents:1 across:4191228k FS > Adding 4191228k swap on /dev/vda5. Priority:-1 extents:1 across:4191228k FS > BUG: Bad rss-counter state mm:ffff880058d2e580 idx:1 val:512 > Adding 4191228k swap on /dev/vda5. Priority:-1 extents:1 across:4191228k FS > Adding 4191228k swap on /dev/vda5. Priority:-1 extents:1 across:4191228k FS > > > > Adding 4191228k swap on /dev/vda5. Priority:-1 extents:1 across:4191228k FS > Adding 4191228k swap on /dev/vda5. Priority:-1 extents:1 across:4191228k FS > Adding 4191228k swap on /dev/vda5. Priority:-1 extents:1 across:4191228k FS > BUG: Bad rss-counter state mm:ffff880046980700 idx:1 val:511 > BUG: Bad rss-counter state mm:ffff880046980700 idx:2 val:1 Hm. I was not able to trigger this and don't see anything obviuous what can lead to this kind of missmatch :-/ I found one more bug: clearing of PageTail can be visible to other CPUs before updated page->flags on the page. I don't think this bug is connected to what you've reported, but worth testing. diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 5e0fe82a0fae..12bd8c5a4409 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2934,6 +2934,13 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, smp_wmb(); /* make pte visible before pmd */ pmd_populate(mm, pmd, pgtable); + + if (freeze) { + for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { + page_remove_rmap(page + i, false); + put_page(page + i); + } + } } void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, @@ -3079,6 +3086,8 @@ static void freeze_page_vma(struct vm_area_struct *vma, struct page *page, if (pte_soft_dirty(entry)) swp_pte = pte_swp_mksoft_dirty(swp_pte); set_pte_at(vma->vm_mm, address, pte + i, swp_pte); + page_remove_rmap(page, false); + put_page(page); } pte_unmap_unlock(pte, ptl); } @@ -3117,8 +3126,6 @@ static void unfreeze_page_vma(struct vm_area_struct *vma, struct page *page, return; pte = pte_offset_map_lock(vma->vm_mm, pmd, address, &ptl); for (i = 0; i < HPAGE_PMD_NR; i++, address += PAGE_SIZE, page++) { - if (!page_mapped(page)) - continue; if (!is_swap_pte(pte[i])) continue; @@ -3128,6 +3135,9 @@ static void unfreeze_page_vma(struct vm_area_struct *vma, struct page *page, if (migration_entry_to_page(swp_entry) != page) continue; + get_page(page); + page_add_anon_rmap(page, vma, address, false); + entry = pte_mkold(mk_pte(page, vma->vm_page_prot)); entry = pte_mkdirty(entry); if (is_write_migration_entry(swp_entry)) @@ -3181,8 +3191,6 @@ static int __split_huge_page_tail(struct page *head, int tail, */ atomic_add(mapcount + 1, &page_tail->_count); - /* after clearing PageTail the gup refcount can be released */ - smp_mb__after_atomic(); page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; page_tail->flags |= (head->flags & @@ -3195,6 +3203,12 @@ static int __split_huge_page_tail(struct page *head, int tail, (1L << PG_unevictable))); page_tail->flags |= (1L << PG_dirty); + /* + * After clearing PageTail the gup refcount can be released. + * Page flags also must be visible before we make the page non-compound. + */ + smp_wmb(); + clear_compound_head(page_tail); if (page_is_young(head)) diff --git a/mm/rmap.c b/mm/rmap.c index 35643176bc15..e4f8d9fb1c3d 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1173,20 +1173,12 @@ void do_page_add_anon_rmap(struct page *page, bool compound = flags & RMAP_COMPOUND; bool first; - if (PageTransCompound(page)) { + if (compound) { + atomic_t *mapcount; VM_BUG_ON_PAGE(!PageLocked(page), page); - if (compound) { - atomic_t *mapcount; - - VM_BUG_ON_PAGE(!PageTransHuge(page), page); - mapcount = compound_mapcount_ptr(page); - first = atomic_inc_and_test(mapcount); - } else { - /* Anon THP always mapped first with PMD */ - first = 0; - VM_BUG_ON_PAGE(!page_mapcount(page), page); - atomic_inc(&page->_mapcount); - } + VM_BUG_ON_PAGE(!PageTransHuge(page), page); + mapcount = compound_mapcount_ptr(page); + first = atomic_inc_and_test(mapcount); } else { VM_BUG_ON_PAGE(compound, page); first = atomic_inc_and_test(&page->_mapcount); @@ -1201,7 +1193,6 @@ void do_page_add_anon_rmap(struct page *page, * disabled. */ if (compound) { - VM_BUG_ON_PAGE(!PageTransHuge(page), page); __inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); } -- Kirill A. Shutemov -- 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/