From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B8119C433F5 for ; Wed, 8 Sep 2021 21:51:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9ECE760FDA for ; Wed, 8 Sep 2021 21:51:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235395AbhIHVw0 (ORCPT ); Wed, 8 Sep 2021 17:52:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47378 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235135AbhIHVwZ (ORCPT ); Wed, 8 Sep 2021 17:52:25 -0400 Received: from mail-ed1-x535.google.com (mail-ed1-x535.google.com [IPv6:2a00:1450:4864:20::535]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6D1E9C061575 for ; Wed, 8 Sep 2021 14:51:16 -0700 (PDT) Received: by mail-ed1-x535.google.com with SMTP id g22so4850811edy.12 for ; Wed, 08 Sep 2021 14:51:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=lOg0eq9m0ngC6ZvpqCMi5DobNuxJwzYIoTh8hAOyJJI=; b=pI3iFRPRR7IxXKiMRd4Q/4yo970KKKt5QN52J3RSbLpeoc4SEplV7Oq7pFJ6vCpvjO cMr5iH2bpD2vbNIeGljQFxHmOMW+4e8cE3urS7pK5qd4Kkec7IQmr+jTBA7yO6QDutUK 5gjAbe+j3Z8edT8HoLxAvF9N5rePZA22eGx049gNVP+zMT52lwvpKfCrQwly3OGNHVXv kfT2wnNsfmDkYo8uHp5ng4hy+92nVprEHEdRdKUw5ZnSN0d++/hs3EcQG2IpLOsLglrf kM3xKXDMx7fVUItcgmtdJjVHsZDAL4FC2+FpSyuG0/+CsQ89HUkzkkCpo/5sZyWpR8iO yD1w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=lOg0eq9m0ngC6ZvpqCMi5DobNuxJwzYIoTh8hAOyJJI=; b=uH+uuu9pbKyEhul+e5mUWB62ggw/kw9NiuiD2MWBak02lq9E5a9u7QCV8rlRYE72To r/xefQjqIZ18n2PfoOBv5k6J8tXxLfwrbajh4w0xKGux4HIwVsx5IhWYwiKHNEzGthoP SW5LpNxRP9z+HcuPWFrb5zoxLUVV2xl7fBBufgC4TxzlLed5C7EXX7F3ETDTD7CZdnEP pFDL3HfI2LaQujNGUDPxyGi3PBjYNFalcuq7fv7EG1B0m9AB9uwWGV2cGnHA+VTU2xw0 RNlcjqNJxIZnyb89kZkE4FlraEqEC8dltkIXY51P+qOcB+8vDuOzGSnU8qJAYkrsnAts Ft2Q== X-Gm-Message-State: AOAM531kDZhN/YqLMhm/S0+e+tfU3R8DntNKHHITDd0Km2p1ij/HWufs XOhCFKIG9qzqTZfR1/T7sOc2gzg2rpoRmntAkRl+3pfc X-Google-Smtp-Source: ABdhPJz/qmVMGpvj1S8/yftdjlo204SKB98R6t6+v10kcPKUJUGNAUxc2a5jYYiPoqbTE0MCREyklIjZPj4PxGjcYEk= X-Received: by 2002:aa7:c882:: with SMTP id p2mr429479eds.46.1631137875036; Wed, 08 Sep 2021 14:51:15 -0700 (PDT) MIME-Version: 1.0 References: <20210906121200.57905-1-rongwei.wang@linux.alibaba.com> <20210906121200.57905-3-rongwei.wang@linux.alibaba.com> <44BE85B4-692C-41E8-B5A0-C1E0B0272ACD@linux.alibaba.com> In-Reply-To: <44BE85B4-692C-41E8-B5A0-C1E0B0272ACD@linux.alibaba.com> From: Yang Shi Date: Wed, 8 Sep 2021 14:51:02 -0700 Message-ID: Subject: Re: [PATCH 2/2] mm, thp: bail out early in collapse_file for writeback page To: Rongwei Wang Cc: Linux MM , Linux Kernel Mailing List , Andrew Morton , cfijalkovich@google.com, song@kernel.org, william.kucharski@oracle.com, Hugh Dickins , "Kirill A. Shutemov" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 7, 2021 at 7:16 PM Rongwei Wang wrote: > > > > On Sep 8, 2021, at 12:56 AM, Yang Shi wrote: > > On Mon, Sep 6, 2021 at 5:12 AM Rongwei Wang > wrote: > > > Currently collapse_file does not explicitly check PG_writeback, instead, > page_has_private and try_to_release_page are used to filter writeback > pages. This does not work for xfs with blocksize equal to or larger > > > I'm not quite sure if using try_to_release() to check the writeback > flag is on purpose or not, but it should be better to check the flag > more explicitly. > > Uh-huh. It is sure that try_to_release_page will check the writeback flag > of page. But the place where check the writeback flag using: > > If (page_has_private(page) && > !try_to_release_page(page, GFP_KERNEL)) { > ... > } > > The original code will miss the page which in writeback status but has no= private data. > The XFS case that above mentioned belongs to. > > Thanks! > > > than pagesize, because in such case xfs has no page->private. > > This makes collapse_file bail out early for writeback page. Otherwise, > xfs end_page_writeback will panic as follows. > > [ 6411.448211] page:fffffe00201bcc80 refcount:0 mapcount:0 mapping:ffff00= 03f88c86a8 index:0x0 pfn:0x84ef32 > [ 6411.448304] aops:xfs_address_space_operations [xfs] ino:30000b7 dentry= name:"libtest.so" > [ 6411.448312] flags: 0x57fffe0000008027(locked|referenced|uptodate|activ= e|writeback) > [ 6411.448317] raw: 57fffe0000008027 ffff80001b48bc28 ffff80001b48bc28 ff= ff0003f88c86a8 > [ 6411.448321] raw: 0000000000000000 0000000000000000 00000000ffffffff ff= ff0000c3e9a000 > [ 6411.448324] page dumped because: VM_BUG_ON_PAGE(((unsigned int) page_r= ef_count(page) + 127u <=3D 127u)) > [ 6411.448327] page->mem_cgroup:ffff0000c3e9a000 > [ 6411.448340] ------------[ cut here ]------------ > [ 6411.448343] kernel BUG at include/linux/mm.h:1212! > [ 6411.449288] Internal error: Oops - BUG: 0 [#1] SMP > [ 6411.449786] Modules linked in: > [ 6411.449790] BUG: Bad page state in process khugepaged pfn:84ef32 > [ 6411.450143] xfs(E) > [ 6411.450459] page:fffffe00201bcc80 refcount:0 mapcount:0 mapping:0 inde= x:0x0 pfn:0x84ef32 > [ 6411.451361] libcrc32c(E) rfkill(E) aes_ce_blk(E) crypto_simd(E) crypt= d(E) aes_ce_cipher(E) crct10dif_ce(E) ghash_ce(E) sha1_ce(E) uio_pdrv_genir= q(E) uio(E) vfat(E) nfsd(E) fat(E) auth_rpcgss(E) nfs_acl(E) lockd(E) grace= (E) sunrpc(E) sch_fq_codel(E) ip_tables(E) ext4(E) mbcache(E) jbd2(E) virti= o_net(E) net_failover(E) virtio_blk(E) failover(E) sha2_ce(E) sha256_arm64(= E) virtio_mmio(E) virtio_pci(E) virtio_ring(E) virtio(E) > [ 6411.451387] CPU: 25 PID: 0 Comm: swapper/25 Kdump: loaded Tainted: G = W E > [ 6411.451389] pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=3D--) > [ 6411.451393] pc : end_page_writeback+0x1c0/0x214 > [ 6411.451394] lr : end_page_writeback+0x1c0/0x214 > [ 6411.451395] sp : ffff800011ce3cc0 > [ 6411.451396] x29: ffff800011ce3cc0 x28: 0000000000000000 > [ 6411.451398] x27: ffff000c04608040 x26: 0000000000000000 > [ 6411.451399] x25: ffff000c04608040 x24: 0000000000001000 > [ 6411.451401] x23: ffff0003f88c8530 x22: 0000000000001000 > [ 6411.451403] x21: ffff0003f88c8530 x20: 0000000000000000 > [ 6411.451404] x19: fffffe00201bcc80 x18: 0000000000000030 > [ 6411.451406] x17: 0000000000000000 x16: 0000000000000000 > [ 6411.451407] x15: ffff000c018f9760 x14: ffffffffffffffff > [ 6411.451409] x13: ffff8000119d72b0 x12: ffff8000119d6ee3 > [ 6411.451410] x11: ffff8000117b69b8 x10: 00000000ffff8000 > [ 6411.451412] x9 : ffff800010617534 x8 : 0000000000000000 > [ 6411.451413] x7 : ffff8000114f69b8 x6 : 000000000000000f > [ 6411.451415] x5 : 0000000000000000 x4 : 0000000000000000 > [ 6411.451416] x3 : 0000000000000400 x2 : 0000000000000000 > [ 6411.451418] x1 : 0000000000000000 x0 : 0000000000000000 > [ 6411.451420] Call trace: > [ 6411.451421] end_page_writeback+0x1c0/0x214 > [ 6411.451424] iomap_finish_page_writeback+0x13c/0x204 > [ 6411.451425] iomap_finish_ioend+0xe8/0x19c > [ 6411.451426] iomap_writepage_end_bio+0x38/0x50 > [ 6411.451427] bio_endio+0x168/0x1ec > [ 6411.451430] blk_update_request+0x278/0x3f0 > [ 6411.451432] blk_mq_end_request+0x34/0x15c > [ 6411.451435] virtblk_request_done+0x38/0x74 [virtio_blk] > [ 6411.451437] blk_done_softirq+0xc4/0x110 > [ 6411.451439] __do_softirq+0x128/0x38c > [ 6411.451441] __irq_exit_rcu+0x118/0x150 > [ 6411.451442] irq_exit+0x1c/0x30 > [ 6411.451445] __handle_domain_irq+0x8c/0xf0 > [ 6411.451446] gic_handle_irq+0x84/0x108 > [ 6411.451447] el1_irq+0xcc/0x180 > [ 6411.451448] arch_cpu_idle+0x18/0x40 > [ 6411.451450] default_idle_call+0x4c/0x1a0 > [ 6411.451453] cpuidle_idle_call+0x168/0x1e0 > [ 6411.451454] do_idle+0xb4/0x104 > [ 6411.451455] cpu_startup_entry+0x30/0x9c > [ 6411.451458] secondary_start_kernel+0x104/0x180 > [ 6411.451460] Code: d4210000 b0006161 910c8021 94013f4d (d4210000) > [ 6411.451462] ---[ end trace 4a88c6a074082f8c ]--- > [ 6411.451464] Kernel panic - not syncing: Oops - BUG: Fatal exception in= interrupt > > Fixes: eb6ecbed0aa2 ("mm, thp: relax the VM_DENYWRITE constraint on file-= backed THPs") > Signed-off-by: Xu Yu > Signed-off-by: Rongwei Wang > --- > mm/khugepaged.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 045cc57..529b117 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1798,7 +1798,8 @@ static void collapse_file(struct mm_struct *mm, > goto out_unlock; > } > > - if (!is_shmem && PageDirty(page)) { > + if (!is_shmem && (PageDirty(page) || > + PageWriteback(page))) { > > > Why not check the writeback flag in the place before taking page lock too= ? > > Thanks! Your words remind me. I will double check the writeback flag befo= re > and after taking page lock. Likes: > > + } else if (PageWriteback(page)) { > + xas_unlock_irq(&xas); > + result =3D SCAN_FAIL; > + goto xa_unlocked; > } else if (trylock_page(page)) { > get_page(page); > xas_unlock_irq(&xas); > @@ -1798,7 +1802,8 @@ static void collapse_file(struct mm_struct *mm, > goto out_unlock; > } > > - if (!is_shmem && PageDirty(page)) { > + if (!is_shmem && (PageDirty(page) || > + PageWriteback(page))) { Yeah, this is what I meant. Thanks. > > Thanks! > > > /* > * khugepaged only works on read-only fd, so this > * page is dirty because it hasn't been flushed > -- > 1.8.3.1 > >