On Wed, Dec 25, 2019 at 08:17:29AM +0000, Justin He wrote:
> Hi Murphy
>
> > -----Original Message-----
> > From: Murphy Zhou <[email protected]>
> > Sent: Wednesday, December 25, 2019 1:42 PM
> > To: [email protected]; Justin He <[email protected]>; Ross Zwisler
> > <[email protected]>
> > Subject: [PATCH] mm: get rid of WARN if failed to cow user pages
> >
> > By running xfstests with fsdax enabled, generic/437 always hits this
> > warning[1] since this commit:
> >
> > commit 83d116c53058d505ddef051e90ab27f57015b025
> > Author: Jia He <[email protected]>
> > Date: Fri Oct 11 22:09:39 2019 +0800
> >
> > mm: fix double page fault on arm64 if PTE_AF is cleared
> >
> > Looking at the test program[2] generic/437 uses, it's pretty easy
> > to hit this warning. Remove this WARN as it seems not necessary.
> >
> > [2] https://git.kernel.org/pub/scm/fs/xfs/xfstests-
> > dev.git/tree/src/t_mmap_cow_race.c
> > [1] warning message:
> > -----------------------------------------------------------------------
> > [ 97.344077] WARNING: CPU: 0 PID: 2486 at mm/memory.c:2281
> It is hard for me to reproduce it in my x86 desktop when running that
> generic/437
>
> Could you please share your test env? E.g. guest or host? What is the
> test_dev of
> your xfstests? Is it a 100% reproducible issue?
It's a kvm guest, with pmem ramdisks. 100% reproducible.
[root@8u ~]# uname -r
5.5.0-rc3-v5.5-rc3
[root@8u ~]# cat /proc/cmdline
BOOT_IMAGE=(hd0,msdos2)/boot/vmlinuz-5.5.0-rc3-v5.5-rc3
root=UUID=62b76d7e-e314-4400-9ea7-ded0de2f9fca ro crashkernel=auto
resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/swap console=ttyS0,115200
memmap=5G!6G memmap=5G!13G
[root@8u ~]# lspci
00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 03)
00:02.0 VGA compatible controller: Red Hat, Inc. QXL paravirtual graphic card
(rev 04)
00:03.0 Ethernet controller: Realtek Semiconductor Co., Ltd.
RTL-8100/8101L/8139 PCI Fast Ethernet Adapter (rev 20)
00:04.0 Audio device: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family)
High Definition Audio Controller (rev 01)
00:05.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI
Controller #1 (rev 03)
00:05.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI
Controller #2 (rev 03)
00:05.2 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI
Controller #3 (rev 03)
00:05.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI
Controller #1 (rev 03)
00:06.0 Communication controller: Red Hat, Inc. Virtio console
00:07.0 Unclassified device [00ff]: Red Hat, Inc. Virtio memory balloon
00:08.0 Ethernet controller: Realtek Semiconductor Co., Ltd.
RTL-8100/8101L/8139 PCI Fast Ethernet Adapter (rev 20)
[root@8u ~]#
[root@8u ~]# ndctl list
[
{
"dev":"namespace0.0",
"mode":"fsdax",
"map":"mem",
"size":5368709120,
"sector_size":512,
"blockdev":"pmem0"
}
]
[root@8u ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 620G 0 disk
├─sda1 8:1 0 2G 0 part
│ └─rhel-swap 253:0 0 2G 0 lvm [SWAP]
└─sda2 8:2 0 618G 0 part /
sdb 8:16 0 200G 0 disk /home
sdc 8:32 0 20G 0 disk
├─sdc1 8:33 0 10G 0 part
└─sdc2 8:34 0 10G 0 part
pmem0 259:0 0 5G 0 disk
├─pmem0p1 259:1 0 2.4G 0 part
└─pmem0p2 259:2 0 2.6G 0 part
[root@8u ~]#
[root@8u xfstests-dev (master)]# cat local.config
TEST_DEV=/dev/pmem0p1
TEST_DIR=/test2
SCRATCH_DEV=/dev/pmem0p2
SCRATCH_MNT=/test1
FSTYP=xfs
MOUNT_OPTIONS="-o dax"
TEST_FS_MOUNT_OPTS="-o dax"
MKFS_OPTIONS="-f -b size=4096 -m reflink=0"
LOGWRITES_DEV=""
[root@8u xfstests-dev (master)]#
>
> Besides, a few days ago, syzbot reported a similar issue, Kirill relied his
> concerns
> at [1]
>
> [1] https://www.spinics.net/lists/linux-mm/msg199008.html
>
> --
> Cheers,
> Justin (Jia He)
>
>
> > wp_page_copy+0x687/0x6e0
> > [ 97.348354] Modules linked in: nf_tables nfnetlink rfkill sunrpc
> > snd_hda_codec_generic ledtrig_audio qxl snd_hda_intel snd_intel_dspcfg
> > drm_ttm_helper snd_hda_codec ttm snd_hda_core drm_kms_helper
> > snd_hwdep snd_seq syscopyarea sysfillrect sysimgblt snd_seq_device
> > fb_sys_fops snd_pcm drm snd_timer crc32_pclmul snd soundcore
> > dax_pmem_compat i2c_piix4 device_dax virtio_balloon pcspkr joydev
> > dax_pmem_core ip_tables xfs libcrc32c crct10dif_pclmul crc32c_intel sd_mod
> > sg ata_generic 8139too ata_piix libata ghash_clmulni_intel 8139cp
> > virtio_console serio_raw nd_pmem mii dm_mirror dm_region_hash dm_log
> > dm_mod
> > [ 97.382176] CPU: 0 PID: 2486 Comm: t_mmap_cow_race Tainted: G W
> > 5.5.0-rc3-v5.5-rc3 #1
> > [ 97.387804] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
> > [ 97.392228] RIP: 0010:wp_page_copy+0x687/0x6e0
> > [ 97.396572] Code: 95 f5 00 48 81 e6 00 f0 ff ff ba 00 10 00 00 49 c1 ff
> > 06 49
> > c1 e7 0c 4c 03 3d 35 95 f5 00 4c 89 ff e8 8d 85 6a 00 85 c0 74 0a <0f> 0b
> > 4c 89
> > ff e8 8f 80 6a 00 65 48 8b 04 25 40 7f 01 00 83 a8 d8
> > [ 97.413487] RSP: 0000:ffffb882493afd28 EFLAGS: 00010206
> > [ 97.417520] RAX: 0000000000001000 RBX: ffffb882493afdf8 RCX:
> > 0000000000001000
> > [ 97.422295] RDX: 0000000000001000 RSI: 00007f1d20c00000 RDI:
> > ffff976384d1f000
> > [ 97.426914] RBP: 0000000000000000 R08: 0000000000000000 R09:
> > 00000000000ca308
> > [ 97.431746] R10: 0000000000000000 R11: ffffe0cd4c1347c0 R12:
> > ffffe0cd4c1347c0
> > [ 97.436371] R13: ffff9763b46ba190 R14: ffff9763a963d0c0 R15:
> > ffff976384d1f000
> > [ 97.441085] FS: 00007f1d203fe700(0000) GS:ffff9763b8a00000(0000)
> > knlGS:0000000000000000
> > [ 97.445500] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [ 97.448393] CR2: 00007f1d20c00000 CR3: 0000000333dfc000 CR4:
> > 00000000000006f0
> > [ 97.452346] Call Trace:
> > [ 97.453681] ? __switch_to_asm+0x34/0x70
> > [ 97.455566] ? __switch_to_asm+0x40/0x70
> > [ 97.457418] ? __switch_to_asm+0x34/0x70
> > [ 97.459197] ? __switch_to_asm+0x40/0x70
> > [ 97.460971] ? __switch_to_asm+0x34/0x70
> > [ 97.462746] ? __switch_to_asm+0x40/0x70
> > [ 97.464561] ? __switch_to_asm+0x34/0x70
> > [ 97.466342] ? __switch_to_asm+0x40/0x70
> > [ 97.468141] do_wp_page+0x8c/0x640
> > [ 97.469818] ? finish_task_switch+0x77/0x2a0
> > [ 97.471631] __handle_mm_fault+0xa06/0x1420
> > [ 97.473517] handle_mm_fault+0xae/0x1d0
> > [ 97.475168] __do_page_fault+0x27f/0x4e0
> > [ 97.476947] do_page_fault+0x30/0x110
> > [ 97.478490] async_page_fault+0x39/0x40
> > [ 97.480275] RIP: 0033:0x400d68
> > [ 97.481587] Code: 53 48 89 fb 48 83 ec 10 66 2e 0f 1f 84 00 00 00 00 00
> > 0f
> > b6 03 ba 04 00 00 00 be 00 00 20 00 48 89 df 89 44 24 0c 8b 44 24 0c <88> 03
> > e8 71 fc ff ff 85 c0 78 30 e8 b8 fc ff ff 89 c7 41 f7 ec 89
> > [ 97.489326] RSP: 002b:00007f1d203fded0 EFLAGS: 00010202
> > [ 97.491336] RAX: 0000000000000001 RBX: 00007f1d20c00000 RCX:
> > 0000000000000000
> > [ 97.494080] RDX: 0000000000000004 RSI: 0000000000200000 RDI:
> > 00007f1d20c00000
> > [ 97.497244] RBP: 0000000000000002 R08: 00007f1d2138d230 R09:
> > 00007f1d2138d260
> > [ 97.500028] R10: 00007f1d203fe9d0 R11: 0000000000000000 R12:
> > 0000000051eb851f
> > [ 97.502785] R13: 00007fff01d5607f R14: 0000000000000000 R15:
> > 00007f1d203fdfc0
> > [ 97.505546] ---[ end trace 18f1c94bd7c3d1e1 ]---
> >
> > Signed-off-by: Murphy Zhou <[email protected]>
> > ---
> > mm/memory.c | 14 ++++----------
> > 1 file changed, 4 insertions(+), 10 deletions(-)
> >
> > diff --git a/mm/memory.c b/mm/memory.c
> > index 45442d9..e3a1dce 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -2269,18 +2269,12 @@ static inline bool cow_user_page(struct page
> > *dst, struct page *src,
> >
> > /*
> > * This really shouldn't fail, because the page is there
> > - * in the page tables. But it might just be unreadable,
> > - * in which case we just give up and fill the result with
> > - * zeroes.
> > + * in the page tables. But it could happen during races,
> > + * or it might just be unreadable, in which cases we
> > + * just give up and fill the result with zeroes.
> > */
> > - if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) {
> > - /*
> > - * Give a warn in case there can be some obscure
> > - * use-case
> > - */
> > - WARN_ON_ONCE(1);
> > + if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
> > clear_page(kaddr);
> > - }
> >
> > ret = true;
> >
> > --
> > 1.8.3.1
>
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