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Re: 4.0 kernel XFS filesystem crash when running AIM7's disk workload

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: 4.0 kernel XFS filesystem crash when running AIM7's disk workload
From: Waiman Long <waiman.long@xxxxxx>
Date: Wed, 22 Apr 2015 13:45:21 -0400
Cc: xfs@xxxxxxxxxxx, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20150421215927.GK21261@dastard>
References: <55314529.7060202@xxxxxx> <20150417234541.GG21261@dastard> <5536B895.1040107@xxxxxx> <20150421215927.GK21261@dastard>
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On 04/21/2015 05:59 PM, Dave Chinner wrote:
On Tue, Apr 21, 2015 at 04:52:37PM -0400, Waiman Long wrote:
On 04/17/2015 07:45 PM, Dave Chinner wrote:
On Fri, Apr 17, 2015 at 01:38:49PM -0400, Waiman Long wrote:
Hi Dave,

When I was running the AIM7's disk workload on a 8-socket
Westmere-EX server with 4.0 kernel, the kernel crash. A set of small
ramdisks were created (ramdisk_size=271072). Those ramdisks were
formatted with XFS filesystem before the test began. The kernel log
was:

XFS (ram12): Mounting V4 Filesystem
XFS (ram12): Log size 1424 blocks too small, minimum size is 1596 blocks
XFS (ram12): Log size out of supported range. Continuing onwards,
but if log hangs are
experienced then please report this message in the bug report.
First thing you need to do is upgrade xfsprogs so that this message
goes away. or use "mkfs.xfs -l size=10m" so that the log is larger
than the minimum.

XFS (ram15): Ending clean mount
BUG: unable to handle kernel NULL pointer dereference at           (null)
IP: [<ffffffff812abd6d>] __memcpy+0xd/0x110
PGD 29f7655f067 PUD 29f75a80067 PMD 0
Oops: 0000 [#1] SMP
Modules linked in: xfs exportfs libcrc32c ebtable_nat ebtables
xt_CHECKSUM iptable_mangle bridge stp llc autofs4 ipt_REJECT
nf_reject_ipv4 nf_conntrack_ipv4 nf_defrag_ipv4 iptable_filter
ip_tables ip6t_REJECT nf_reject_ipv6 nf_conntrack_ipv6
nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables ipv6
vhost_net macvtap macvlan vhost tun kvm_intel kvm ipmi_si
ipmi_msghandler tpm_infineon iTCO_wdt iTCO_vendor_support wmi
acpi_cpufreq microcode pcspkr serio_raw qlcnic be2net vxlan
udp_tunnel ip6_udp_tunnel ses enclosure igb dca ptp pps_core lpc_ich
mfd_core hpilo hpwdt sg i7core_edac edac_core netxen_nic ext4(E)
jbd2(E) mbcache(E) sr_mod(E) cdrom(E) sd_mod(E) lpfc(E) qla2xxx(E)
scsi_transport_fc(E) pata_acpi(E) ata_generic(E) ata_piix(E) hpsa(E)
radeon(E) ttm(E) drm_kms_helper(E) drm(E) i2c_algo_bit(E)
i2c_core(E) dm_mirror(E) dm_region_hash(E) dm_log(E) dm_mod(E)
Why do you have a mix of signed and unsigned modules loaded?
I did the test on a RHEL 6.6 system. The 4.0 kernel is unsigned, but
there are some additional RHEL modules loaded at boot up time.
Wait, what?

Do you have rhel 6.6 modules loaded into a 4.0 kernel? If so, I'd
suggest you fix things so that doesn't happen before running any
more tests...

No, I didn't. I thought the system startup scripts may have loaded some additional kernel modules, but I didn't check to see if it is really the case. Anyway, this is not the issue that was causing problem that I saw.


823        case XFS_DINODE_FMT_LOCAL:
824            if ((iip->ili_fields&   dataflag[whichfork])&&
    0x00000000000023c0<+336>:    movslq %ecx,%rcx
    0x00000000000023c3<+339>:    movswl 0x0(%rcx,%rcx,1),%eax
    0x00000000000023cb<+347>:    test   %eax,0x90(%rdx)
    0x00000000000023d1<+353>:    je     0x2350<xfs_iflush_fork+224>

825                (ifp->if_bytes>   0)) {
    0x00000000000023d7<+359>:    mov    (%r10),%edx
    0x00000000000023da<+362>:    test   %edx,%edx
    0x00000000000023dc<+364>:    jle    0x2350<xfs_iflush_fork+224>
So the contents of rdx says that the inode fork size is 6 bytes in
local format. The call location also indicates that it is the
attribute fork that is in being flushed. The minimum size of the
attr fork is 3 bytes - an empty header. However, then ext valid size
has a second header that adds 4 bytes to the size, plus the bytes
inteh attr name and value.

Hence a size of 6 bytes is invalid, and probably indicates that
there is some form of memory corruption going on here.

IIRC, we haven't touched this code for a while - can you test 3.19
and see if it has the same problem? If it doesn't have the problem,
and given you can reliably reproduce the crash, can you run a
bisect to find the cause?
I have done the bisection and the following commit in 3.13 is the
one that cause the problem, I think:

f7be2d7f594cbc7a00902b5427332a1ad519a528
xfs: push down inactive transaction mgmt for truncate

I looked at the patch, and it didn't seem quite right,
In what way?

but I don't
know much about the XFS internal to be sure. Maybe you can take a
look at that.
Doesn't actually seem very likely - that's mostly just a factoring
patch, and it is called on every inode that is reclaimed from
memory, so it's not like that code path doesn't get well tested....

So, I'm confused - I thought you were reporting a recent regression.
Are you actually reporting a regression between a RHEL 6.6 kernel
and the current mainline kernel?  Is this the first time you've run
this test on XFS on a kernel more recent than RHEL6.6?

Details, please; they are important.

http://xfs.org/index.php/XFS_FAQ#Q:_What_information_should_I_include_when_reporting_a_problem.3F

Cheers,

Dave.

I have just sent out a patch to fix this problem. Please let me know if there is any problem with the patch.

Cheers,
Longman

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