Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752185AbaAOQG7 (ORCPT ); Wed, 15 Jan 2014 11:06:59 -0500 Received: from www62.your-server.de ([213.133.104.62]:59342 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751864AbaAOQGx (ORCPT ); Wed, 15 Jan 2014 11:06:53 -0500 Message-ID: <52D6B213.4020602@iogearbox.net> Date: Wed, 15 Jan 2014 17:06:43 +0100 From: Daniel Borkmann User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Vlastimil Babka CC: Andrew Morton , linux-kernel , Michel Lespinasse , linux-mm , Jared Hulbert , netdev Subject: Re: [BUG] at include/linux/page-flags.h:415 (PageTransHuge) References: <52D03A9E.2030309@iogearbox.net> <20140110222248.4e8419ca.akpm@linux-foundation.org> <52D147F1.3040803@iogearbox.net> <52D3BCE9.4020405@suse.cz> <52D3D060.1010301@iogearbox.net> <52D69AB4.6000309@suse.cz> In-Reply-To: <52D69AB4.6000309@suse.cz> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated-Sender: borkmann@iogearbox.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [keeping netdev in loop as well] On 01/15/2014 03:27 PM, Vlastimil Babka wrote: > On 01/13/2014 12:39 PM, Daniel Borkmann wrote: >> On 01/13/2014 11:16 AM, Vlastimil Babka wrote: >>> On 01/11/2014 02:32 PM, Daniel Borkmann wrote: >>>> On 01/11/2014 07:22 AM, Andrew Morton wrote: >>>>> On Fri, 10 Jan 2014 19:23:26 +0100 Daniel Borkmann wrote: >>>>> >>>>>> This is being reliably triggered for each mmaped() packet(7) >>>>>> socket from user space, basically during unmapping resp. >>>>>> closing the TX socket. >>>>>> >>>>>> I believe due to some change in transparent hugepages code ? >>>>>> >>>>>> When I disable transparent hugepages, everything works fine, >>>>>> no BUG triggered. >>>>>> >>>>>> I'd be happy to test patches. >>>>> >>>>> Did the inclusion of c424be1cbbf852e46acc8 ("mm: munlock: fix a bug >>>>> where THP tail page is encountered") in current mainline fix this? >>>> >>>> Thanks for your answer Andrew! >>>> >>>> Hm, I just cherry-picked that onto current net-next as I have some work >>>> there, and this time I got ... >>>> >>>> (User space uses packet mmap() and mlockall(MCL_CURRENT | MCL_FUTURE) >>>> and on shutdown munlockall() ...) >>>> >>>> [ 63.863672] ------------[ cut here ]------------ >>>> [ 63.863702] kernel BUG at mm/mlock.c:507! >>>> [ 63.863721] invalid opcode: 0000 [#1] SMP >>>> [ 63.863743] Modules linked in: fuse ebtable_nat xt_CHECKSUM nf_conntrack_netbios_ns nf_conntrack_broadcast ipt_MASQUERADE ip6table_nat nf_nat_ipv6 ip6table_mangle ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 iptable_nat nf_nat_ipv4 nf_nat iptable_mangle nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack bridge ebtable_filter ebtables stp llc ip6table_filter ip6_tables rfcomm bnep snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_intel snd_hda_codec iwlwifi cfg80211 snd_hwdep btusb snd_seq bluetooth sdhci_pci snd_seq_device e1000e tpm_tis snd_pcm thinkpad_acpi sdhci ptp tpm uvcvideo pps_core snd_page_alloc snd_timer snd rfkill mmc_core iTCO_wdt iTCO_vendor_support lpc_ich mfd_core soundcore joydev wmi videobuf2_vmalloc videobuf2_memops videobuf2_core i2c_i801 pcspkr videodev media uinput i915 >>>> [ 63.864152] i2c_algo_bit drm_kms_helper drm i2c_core video >>>> [ 63.864181] CPU: 1 PID: 1617 Comm: trafgen Not tainted 3.13.0-rc6+ #15 >>>> [ 63.864209] Hardware name: LENOVO 2429BP3/2429BP3, BIOS G4ET37WW (1.12 ) 05/29/2012 >>>> [ 63.864242] task: ffff8801ee060000 ti: ffff8800b5954000 task.ti: ffff8800b5954000 >>>> [ 63.864274] RIP: 0010:[] [] munlock_vma_pages_range+0x2ea/0x2f0 >>>> [ 63.864318] RSP: 0018:ffff8800b5955e08 EFLAGS: 00010202 >>>> [ 63.864341] RAX: 00000000000001ff RBX: ffff8800b58f7508 RCX: 0000000000000034 >>>> [ 63.864372] RDX: 00000007f0708992 RSI: ffffea0002c3e700 RDI: ffffea0002c3e700 >>>> [ 63.864402] RBP: ffff8800b5955ee0 R08: 3800000000000000 R09: a8000b0f9c000000 >>>> [ 63.864432] R10: 57ffdef066c3e700 R11: ffffff5cfb00c14a R12: ffffea0002c3e700 >>>> [ 63.864462] R13: ffff8800b5955f48 R14: 00007f0708992000 R15: 00007f0708992000 >>>> [ 63.864492] FS: 00007f0708b92740(0000) GS:ffff88021e240000(0000) knlGS:0000000000000000 >>>> [ 63.864526] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>>> [ 63.864551] CR2: 00007f33bb373000 CR3: 00000000b2a2c000 CR4: 00000000001407e0 >>>> [ 63.864581] Stack: >>>> [ 63.864593] ffff8800b5955ed0 00007f0708b91fff 00007f0708b92000 ffff8800b5955e48 >>>> [ 63.864632] 000001ff810c864b ffff8801ee060000 0000000000000000 0000000000000000 >>>> [ 63.864669] ffff8800b5955e58 ffff8801ee060000 0000000700000086 ffff8801ee060000 >>>> [ 63.864708] Call Trace: >>>> [ 63.864724] [] ? _raw_spin_unlock_irq+0x2c/0x30 >>>> [ 63.864754] [] ? vma_merge+0xc2/0x330 >>>> [ 63.864786] [] mlock_fixup+0xfc/0x190 >>>> [ 63.864812] [] do_mlockall+0x87/0xc0 >>>> [ 63.864836] [] sys_munlockall+0x2f/0x50 >>>> [ 63.864873] [] system_call_fastpath+0x16/0x1b >>>> [ 63.864898] Code: d7 48 89 95 28 ff ff ff e8 a4 04 fe ff 84 c0 48 8b 95 28 ff ff ff 0f 85 5a ff ff ff e9 46 ff ff ff e8 3f ac 51 00 e8 34 ac 51 00 <0f> 0b 0f 1f 40 00 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 41 55 >>>> [ 63.865114] RIP [] munlock_vma_pages_range+0x2ea/0x2f0 >>>> [ 63.865148] RSP >>>> [ 63.874968] ------------[ cut here ]------------ >>>> >>>> ... when I find some time, I'll try with normal torvalds' tree, maybe some >>>> other patches are missing as well, not sure right now. >>> >>> Uh so the triggered assertion is the one added by this very patch, and there are no more changes wrt this in mainline. >>> >>> If you can still try debug patches, please try this. Thanks. >> >> Yes, thanks, I'll come back to you some time by today. > > Daniel sent me (off-list) instructions to reproduce: > >> Then in the kernel source tree, you'll find: >> >> tools/testing/selftests/net/ >> >> There, just do a 'make' and run ./psock_tpacket > > It reproduces deterministically in mainline since 3.12, i.e. my munlock > performance series. Based on the initial debug output, I've expanded the > debug patch below a bit: > >>> From: Vlastimil Babka >>> Date: Mon, 13 Jan 2014 11:13:53 +0100 >>> Subject: [PATCH] debug munlock_vma_pages_range >>> >>> --- >>> mm/mlock.c | 22 ++++++++++++++++++++-- >>> 1 file changed, 20 insertions(+), 2 deletions(-) >>> >>> diff --git a/mm/mlock.c b/mm/mlock.c >>> index c59c420..7d0e29a 100644 >>> --- a/mm/mlock.c >>> +++ b/mm/mlock.c >>> @@ -448,12 +448,14 @@ static unsigned long __munlock_pagevec_fill(struct pagevec *pvec, >>> void munlock_vma_pages_range(struct vm_area_struct *vma, >>> unsigned long start, unsigned long end) >>> { >>> + unsigned long orig_start = start; >>> + unsigned long page_increm = 0; >>> + >>> vma->vm_flags &= ~VM_LOCKED; >>> >>> while (start < end) { >>> struct page *page = NULL; >>> unsigned int page_mask; >>> - unsigned long page_increm; >>> struct pagevec pvec; >>> struct zone *zone; >>> int zoneid; >>> @@ -504,7 +506,23 @@ void munlock_vma_pages_range(struct vm_area_struct *vma, >>> } >>> } >>> /* It's a bug to munlock in the middle of a THP page */ >>> - VM_BUG_ON((start >> PAGE_SHIFT) & page_mask); >>> + if ((start >> PAGE_SHIFT) & page_mask) { >>> + dump_page(page); >>> + printk("start=%lu pfn=%lu orig_start=%lu " >>> + "prev_page_increm=%lu page_mask=%u " >>> + "vm_start=%lu vm_end=%lu vm_flags=%lu\n", >>> + start, page_to_pfn(page), orig_start, >>> + page_increm, page_mask, >>> + vma->vm_start, vma->vm_end, >>> + vma->vm_flags); > + printk("vm_ops=%pF, open=%pF, fault=%pF, remap_pages=%pF\n", vma->vm_ops, > + vma->vm_ops->open, vma->vm_ops->fault, vma->vm_ops->remap_pages); > + if (PageCompound(page)) { > + printk("page is compound with order=%d\n", compound_order(page)); > + } >>> + if (PageTail(page)) { >>> + struct page *first_page = page->first_page; >>> + printk("first_page pfn=%lu\n", >>> + page_to_pfn(first_page)); >>> + dump_page(first_page); >>> + } >>> + VM_BUG_ON(true); >>> + } >>> page_increm = 1 + page_mask; >>> start += page_increm * PAGE_SIZE; >>> next: >>> > > And got output like this: > > page:ffffea0002474a40 count:5 mapcount:1 mapping: (null) index:0x0 > page flags: 0x100000000004004(referenced|head) > start=140242647736320 pfn=682616 orig_start=140242647736320 prev_page_increm=0 page_mask=511 vm_start=140242647736320 vm_end=140242651930624 vm_flags=268435707 > vm_ops=packet_mmap_ops+0x0/0xfffffffffffff8e0 [af_packet], open=packet_mm_open+0x0/0x30 [af_packet], fault= (null), remap_pages= (null) > page is compound with order=2 > > Observations: > - address 140242647736320 is where the vma starts, and is not aligned to 512 pages > (so it cannot be a THP head which the munlock expects). Yet there is a head page > that triggers the PageTransHuge() and consequently hpage_nr_pages() in munlock_vma_page() > That's why page_mask is determined to be 511 and the code thinks it's in the > middle of a THP page. > - in fact, the page is a compound page with order=2 > - the VM flags (except (may)read/write) are VM_SHARED and VM_MIXEDMAP > - the vma was mmapped by packet_mmap() (net/packet/af_packet.c) which uses > vm_insert_page(), which adds the VM_MIXEDMAP flag > - the buffers that are mapped were allocated by alloc_one_pg_vec_page() > where flags indeed include __GFP_COMP > > So clearly there is a way to have mlock/munlock operate on a vma that contains > compound pages and confuse the checks for PageTransHuge(). > > The checks for THP in munlock came with commit ff6a6da60b89 ("mm: accelerate munlock() > treatment of THP pages"), i.e. since 3.9, but did not trigger a bug. It however > makes munlock_vma_pages_range() skip pages until the next 512-pages-aligned page, > when it encounters a head page. If the head page is of smaller order and is followed > by normal LRU pages (theoretically, I'm not sure if that's possible, or done anywhere), > they wouldn't get munlocked. > > My commit 7225522bb429 ("mm: munlock: batch non-THP page isolation and > munlock+putback using pagevec") (since 3.12) has added a new PageTransHuge() check > that can trigger on tail pages of the compound page here. Commit c424be1cbbf852e46acc8 > ("mm: munlock: fix a bug where THP tail page is encountered") in current rc's removes > one class of bugs here, but still non-THP compound pages are not expected in mlock/munlock, > which leads to this assertion failing. > > The question is what is the correct fix, and I'm not that familiar with VM_MIXEDMAP > to decide. > > Option 1: mlocking VM_MIXEDMAP vma's has no sense. They should be treated like VM_PFNMAP > and added to VM_SPECIAL, which makes m(un)lock skip them completely. > > Option 2: if indeed VM_MIXEDMAP can contain PageLRU pages for which mlocking is useful, > VM_NO_THP should be checked in munlock before attempting PageTransHuge() and > friends. VM_NO_THP already contains VM_MIXEDMAP, so knowing that there can be > no THP means we don't try optimize for it and no unexpected head pages trip us. > > Thoughts? -- 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/