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Date:   Tue, 21 Jun 2022 15:43:44 -0700
From:   Zach O'Keefe <zokeefe@google.com>
To:     Mike Kravetz <mike.kravetz@oracle.com>
Cc:     Yang Shi <shy828301@gmail.com>, vbabka@suse.cz,
        kirill.shutemov@linux.intel.com, willy@infradead.org,
        linmiaohe@huawei.com, akpm@linux-foundation.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [mm-unstable v5 PATCH 0/7] Cleanup transhuge_xxx helpers
Message-ID: <YrJJoP5vrZflvwd0@google.com>
References: <20220616174840.1202070-1-shy828301@gmail.com>
 <YrIzEZxuwQAi7VR1@monkey>
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On 21 Jun 14:07, Mike Kravetz wrote:
> On 06/16/22 10:48, Yang Shi wrote:
> > This series is the follow-up of the discussion about cleaning up transhuge_xxx
> > helpers at https://lore.kernel.org/linux-mm/627a71f8-e879-69a5-ceb3-fc8d29d2f7f1@suse.cz/.
> > 
> > THP has a bunch of helpers that do VMA sanity check for different paths, they
> > do the similar checks for the most callsites and have a lot duplicate codes.
> > And it is confusing what helpers should be used at what conditions.
> > 
> > This series reorganized and cleaned up the code so that we could consolidate
> > all the checks into hugepage_vma_check().
> > 
> > The transhuge_vma_enabled(), transparent_hugepage_active() and
> > __transparent_hugepage_enabled() are killed by this series.
> 
> Running libhugetlbfs tests on next-20220621 produces the following:
> 
> [   77.436038] BUG: kernel NULL pointer dereference, address: 0000000000000378
> [   77.437278] #PF: supervisor read access in kernel mode
> [   77.438211] #PF: error_code(0x0000) - not-present page
> [   77.439097] PGD 800000017a1a6067 P4D 800000017a1a6067 PUD 17f3b9067 PMD 0 
> [   77.440021] Oops: 0000 [#7] PREEMPT SMP PTI
> [   77.440635] CPU: 1 PID: 2720 Comm: get_huge_pages Tainted: G      D           5.19.0-rc3-next-20220621+ #22
> [   77.441973] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1.fc35 04/01/2014
> [   77.443115] RIP: 0010:hugepage_vma_check+0x15/0x170
> [   77.444021] Code: 01 e9 84 fd ff ff 48 89 d8 e9 14 ff ff ff 0f 1f 80 00 00 00 00 0f 1f 44 00 00 f7 c6 00 00 00 40 0f 85 fe 00 00 00 48 8b 47 10 <48> 8b 80 78 03 00 00 48 c1 e8 18 83 e0 01 0f 85 e6 00 00 00 4c 8b
> [   77.447327] RSP: 0018:ffffc900039dfd20 EFLAGS: 00010246
> [   77.448317] RAX: 0000000000000000 RBX: ffff88817e4b27a0 RCX: 0000000000000000
> [   77.449681] RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffffff823f2000
> [   77.451040] RBP: ffffffff823f2000 R08: 0000000000000008 R09: ffff8881a3c042e6
> [   77.452353] R10: 00007ffe8b341000 R11: ffff8881a3c04526 R12: ffff88817e4b27a0
> [   77.453677] R13: ffffc900039dfd28 R14: ffff88817e4b27c8 R15: ffffffff823f2000
> [   77.455046] FS:  00007f0edc9880c0(0000) GS:ffff888277d00000(0000) knlGS:0000000000000000
> [   77.456625] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   77.457745] CR2: 0000000000000378 CR3: 0000000179394006 CR4: 0000000000370ee0
> [   77.459936] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [   77.461308] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [   77.462477] Call Trace:
> [   77.462950]  <TASK>
> [   77.463402]  show_smap+0xed/0x1c0
> [   77.464019]  seq_read_iter+0x2af/0x480
> [   77.464674]  seq_read+0xeb/0x120
> [   77.465286]  vfs_read+0x97/0x190
> [   77.465880]  ksys_read+0x5f/0xe0
> [   77.466488]  do_syscall_64+0x3b/0x90
> [   77.467155]  entry_SYSCALL_64_after_hwframe+0x46/0xb0
> [   77.468023] RIP: 0033:0x7f0edca7ade2
> [   77.468609] Code: c0 e9 b2 fe ff ff 50 48 8d 3d b2 3f 0a 00 e8 05 f0 01 00 0f 1f 44 00 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 0f 05 <48> 3d 00 f0 ff ff 77 56 c3 0f 1f 44 00 00 48 83 ec 28 48 89 54 24
> [   77.471492] RSP: 002b:00007ffe8b324c28 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
> [   77.472845] RAX: ffffffffffffffda RBX: 00000000022f82a0 RCX: 00007f0edca7ade2
> [   77.474017] RDX: 0000000000000400 RSI: 00000000022f8480 RDI: 0000000000000003
> [   77.475184] RBP: 00007f0edcb4f320 R08: 0000000000000003 R09: 0000000000000000
> [   77.476379] R10: 00007f0edcaffac0 R11: 0000000000000246 R12: 00000000022f82a0
> [   77.477517] R13: 0000000000000d68 R14: 00007f0edcb4e720 R15: 0000000000000d68
> [   77.478590]  </TASK>
> [   77.479012] Modules linked in: rfkill ip6table_filter ip6_tables sunrpc snd_hda_codec_generic snd_hda_intel snd_intel_dspcfg snd_hda_codec snd_hwdep snd_hda_core snd_seq snd_seq_device snd_pcm joydev snd_timer 9p netfs 9pnet_virtio snd soundcore virtio_balloon 9pnet virtio_console virtio_blk virtio_net net_failover failover crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel serio_raw virtio_pci virtio virtio_ring virtio_pci_legacy_dev virtio_pci_modern_dev fuse
> [   77.484573] CR2: 0000000000000378
> [   77.485123] ---[ end trace 0000000000000000 ]---
> 
> 
> Looks to be related to this series.  I'll start debugging unless someone
> knows what the issue may be.
> -- 
> Mike Kravetz

Thanks Mike,

I posted the issue in response to '[v5 PATCH 4/7] mm: thp: kill
transparent_hugepage_active()' of this series[1], where the issue was
introduced.

TLDR: we need to check vma->vm_mm because for vDSO vma, this is NULL.


[1] https://lore.kernel.org/linux-mm/YrIU2iP0H5LQbV7R@google.com/