Date:   Fri, 23 Jun 2017 16:12:27 +0800
From:   Eryu Guan <eguan@...hat.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-nfs@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-ext4@...r.kernel.org, Theodore Ts'o <tytso@....edu>,
        Jan Kara <jack@...e.cz>
Subject: Re: [v4.12-rc1 regression] nfs server crashed in fstests run

On Fri, Jun 23, 2017 at 09:51:56AM +0200, Michal Hocko wrote:
> On Fri 23-06-17 09:43:34, Michal Hocko wrote:
> > [Let's add Jack and keep the full email for reference]
> > 
> > On Fri 23-06-17 15:26:56, Eryu Guan wrote:
> [...]
> > > Then I did further confirmation tests:
> > > 1. switch to a new branch with that jbd2 patch as HEAD and compile
> > > kernel, run test with both ext4 and XFS exported on this newly compiled
> > > kernel, it crashed within 5 iterations.
> > > 
> > > 2. revert that jbd2 patch (when it was HEAD), run test with both ext4
> > > and XFS exported, kernel survived 20 iterations of full fstests run.
> > > 
> > > 3. kernel from step 1 survived 20 iterations of full fstests run, if I
> > > export XFS only (create XFS on /dev/sda4 and mount it at /export/test).
> > > 
> > > 4. 4.12-rc1 kernel survived the same test if I export ext4 only (both
> > > /export/test and /export/scratch were mounted as ext4, and this was done
> > > on another test host because I don't have another spare test partition)
> > > 
> > > 
> > > All these facts seem to confirm that commit 81378da64de6 really is the
> > > culprit, I just don't see how..
> 
> AFAIR, no follow up patches to remove GFP_NOFS have been merged into
> ext4 so we are currently only with 81378da64de6 and all it does is that
> _all_ allocations from the transaction context are implicitly GFP_NOFS.
> I can imagine that if there is a GFP_KERNEL allocation in this context
> (which would be incorrect AFAIU) some shrinkers will not be called as a
> result and that might lead to an observable behavior change. But this
> sounds like a wild speculation. The mere fact that xfs oopses and there
> is no ext code in the backtrace is suspicious on its own. Does this oops
> sound familiar to xfs guys?
> 
> Anyway, I assume that if you revert 81378da64de6 the issue is gone?
> [...]

Correct, the first thing I did after git bisect finished, was reverting
81378da64de6 (with it as HEAD) and re-testing, and it survived 20
iterations of fstests run, as described in above step 1 and 2.

Usually kernel crashed within 5 loops, and 20 loops required around 48
hours to finish, so I think 20 is reasonable and didn't loop for even
longer time.

But I can still be wrong, because it's not a 100% reproduced bug,
there's still chance that 20 iterations are not enough, and reverting
81378da64de6 just made it even harder to reproduce.

Thanks,
Eryu

> 
> > > > [88895.796834] run fstests generic/028 at 2017-06-01 00:43:18
> > > > [88900.945420] run fstests generic/029 at 2017-06-01 00:43:23
> > > > [88901.127315] BUG: unable to handle kernel paging request at ffffffffc0360e12
> > > > [88901.135095] IP: report_bug+0x64/0x100
> > > > [88901.139177] PGD 3b7c0c067
> > > > [88901.139177] P4D 3b7c0c067
> > > > [88901.142194] PUD 3b7c0e067
> > > > [88901.145209] PMD 469e33067
> > > > [88901.148225] PTE 80000004675f4161
> > > > [88901.151240]
> > > > [88901.156497] Oops: 0003 [#1] SMP
> > > > [88901.159997] Modules linked in: loop dm_mod nfsv3 nfs fscache ext4 jbd2 mbcache intel_rapl sb_edac x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm nfsd irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc ipmi_ssif cdc_ether aesni_intel iTCO_wdt usbnet crypto_simd ipmi_si glue_helper sg iTCO_vendor_support wmi mii cryptd ipmi_devintf ipmi_msghandler auth_rpcgss shpchp i2c_i801 pcspkr ioatdma lpc_ich nfs_acl lockd grace sunrpc ip_tables xfs libcrc32c sd_mod mgag200 drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops igb ttm drm ptp pps_core dca megaraid_sas crc32c_intel i2c_algo_bit i2c_core
> > > > [88901.221606] CPU: 9 PID: 3278 Comm: nfsd Not tainted 4.12.0-rc3 #42
> > > > [88901.228500] Hardware name: IBM System x3650 M4 -[7915ON3]-/00J6520, BIOS -[VVE124AUS-1.30]- 11/21/2012
> > > > [88901.238885] task: ffffa10062d12d00 task.stack: ffffc2820478c000
> > > > [88901.245488] RIP: 0010:report_bug+0x64/0x100
> > > > [88901.250153] RSP: 0018:ffffc2820478f598 EFLAGS: 00010202
> > > > [88901.255980] RAX: ffffffffc0360e08 RBX: ffffffffc0301cdc RCX: 0000000000000001
> > > > [88901.263940] RDX: 0000000000000907 RSI: ffffffffc038bc80 RDI: ffffffffffff0d22
> > > > [88901.271901] RBP: ffffc2820478f5b8 R08: 0000000000000001 R09: 00000000000001cc
> > > > [88901.279861] R10: ffffffffb6a36f67 R11: 0000000000000000 R12: ffffc2820478f6e8
> > > > [88901.287821] R13: ffffffffc0351b2a R14: 00000000000003fb R15: 0000000000000004
> > > > [88901.295783] FS:  0000000000000000(0000) GS:ffffa1007f6c0000(0000) knlGS:0000000000000000
> > > > [88901.304818] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > > [88901.311227] CR2: ffffffffc0360e12 CR3: 00000003b7c09000 CR4: 00000000000406e0
> > > > [88901.319188] Call Trace:
> > > > [88901.321920]  do_trap+0x16a/0x190
> > > > [88901.325519]  do_error_trap+0x89/0x110
> > > > [88901.329652]  ? xfs_do_writepage+0x65c/0x680 [xfs]
> > > > [88901.334917]  ? _xfs_buf_find+0x2a2/0x510 [xfs]
> > > > [88901.339875]  ? kmem_cache_alloc+0x194/0x1a0
> > > > [88901.344561]  ? kmem_zone_alloc+0x96/0x100 [xfs]
> > > > [88901.349615]  do_invalid_op+0x20/0x30
> > > > [88901.353604]  invalid_op+0x1e/0x30
> > > > [88901.357318] RIP: 0010:xfs_do_writepage+0x65c/0x680 [xfs]
> > > > [88901.363242] RSP: 0018:ffffc2820478f790 EFLAGS: 00010206
> > > > [88901.369069] RAX: 0000000000340140 RBX: ffffc2820478f8b8 RCX: 0000000000000000
> > > > [88901.377030] RDX: 0000000000000000 RSI: ffffc2820478f9f8 RDI: fffffc2be1095400
> > > > [88901.384991] RBP: ffffc2820478f838 R08: 0000000000000002 R09: 000000000001ff20
> > > > [88901.392950] R10: ffffa1007ffd1d00 R11: 0000000000000000 R12: ffffa10053c2ea58
> > > > [88901.400911] R13: fffffc2be1095400 R14: ffffc2820478f960 R15: ffffc2820478f9f8
> > > > [88901.408876]  ? page_mkclean+0x69/0xb0
> > > > [88901.412960]  ? invalid_page_referenced_vma+0x90/0x90
> > > > [88901.418500]  write_cache_pages+0x26f/0x510
> > > > [88901.423085]  ? xfs_vm_set_page_dirty+0x1d0/0x1d0 [xfs]
> > > > [88901.428819]  ? block_write_end+0x36/0x80
> > > > [88901.433193]  ? generic_write_end+0x54/0xc0
> > > > [88901.437791]  xfs_vm_writepages+0xb6/0xd0 [xfs]
> > > > [88901.442741]  do_writepages+0x1c/0x70
> > > > [88901.446727]  __filemap_fdatawrite_range+0xc6/0x100
> > > > [88901.452071]  filemap_write_and_wait_range+0x41/0x90
> > > > [88901.457532]  xfs_file_fsync+0x63/0x1d0 [xfs]
> > > > [88901.462294]  vfs_fsync_range+0x3d/0xb0
> > > > [88901.466491]  xfs_file_write_iter+0x121/0x140 [xfs]
> > > > [88901.471835]  __do_readv_writev+0x2d3/0x360
> > > > [88901.476402]  do_readv_writev+0x76/0xb0
> > > > [88901.480582]  ? do_dentry_open+0x261/0x310
> > > > [88901.485069]  ? xfs_extent_busy_ag_cmp+0x20/0x20 [xfs]
> > > > [88901.490704]  vfs_writev+0x3c/0x50
> > > > [88901.494409]  nfsd_vfs_write+0xd0/0x360 [nfsd]
> > > > [88901.499271]  ? ima_file_check+0x20/0x30
> > > > [88901.503553]  nfsd_write+0x15a/0x210 [nfsd]
> > > > [88901.508116]  nfsd3_proc_write+0x9d/0x130 [nfsd]
> > > > [88901.513172]  nfsd_dispatch+0xce/0x270 [nfsd]
> > > > [88901.517950]  svc_process_common+0x387/0x740 [sunrpc]
> > > > [88901.523492]  svc_process+0xfc/0x1c0 [sunrpc]
> > > > [88901.528248]  nfsd+0xe9/0x160 [nfsd]
> > > > [88901.532137]  kthread+0x109/0x140
> > > > [88901.535740]  ? nfsd_destroy+0x60/0x60 [nfsd]
> > > > [88901.540501]  ? kthread_park+0x60/0x60
> > > > [88901.544586]  ret_from_fork+0x25/0x30
> > > > [88901.548572] Code: 63 78 04 44 0f b7 70 08 41 89 d0 4c 8d 2c 38 41 83 e0 01 f6 c2 02 74 17 66 45 85 c0 74 11 f6 c2 04 b9 01 00 00 00 75 bb 83 ca 04 <66> 89 50 0a 66 45 85 c0 74 52 0f b6 48 0b 41 0f b7 f6 4d 89 e0
> > > > [88901.569642] RIP: report_bug+0x64/0x100 RSP: ffffc2820478f598
> > > > [88901.575955] CR2: ffffffffc0360e12
> > > > [88901.579663] ---[ end trace 62c63b9fb594e7f4 ]---
> > > > [88901.584811] Kernel panic - not syncing: Fatal exception
> > > > [88901.590694] Kernel Offset: 0x35000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
> > > > [88901.602731] Rebooting in 3 seconds..
> > > > --
> > > > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> > > > the body of a message to majordomo@...r.kernel.org
> > > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > 
> > > # bad: [2ea659a9ef488125eb46da6eb571de5eae5c43f6] Linux 4.12-rc1
> > > # good: [a351e9b9fc24e982ec2f0e76379a49826036da12] Linux 4.11
> > > git bisect start 'v4.12-rc1' 'v4.11'
> > > # good: [221656e7c4ce342b99c31eca96c1cbb6d1dce45f] Merge tag 'sound-4.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound
> > > git bisect good 221656e7c4ce342b99c31eca96c1cbb6d1dce45f
> > > # bad: [c6a677c6f37bb7abc85ba7e3465e82b9f7eb1d91] Merge tag 'staging-4.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging
> > > git bisect bad c6a677c6f37bb7abc85ba7e3465e82b9f7eb1d91
> > > # bad: [e579dde654fc2c6b0d3e4b77a9a4b2d2405c510e] Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
> > > git bisect bad e579dde654fc2c6b0d3e4b77a9a4b2d2405c510e
> > > # bad: [a96480723c287c502b02659f4b347aecaa651ea1] Merge tag 'for-linus-4.12b-rc0b-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip
> > > git bisect bad a96480723c287c502b02659f4b347aecaa651ea1
> > > # good: [16a12fa9aed176444fc795b09e796be41902bb08] Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input
> > > git bisect good 16a12fa9aed176444fc795b09e796be41902bb08
> > > # good: [1684096b1ed813f621fb6cbd06e72235c1c2a0ca] Merge tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dledford/rdma
> > > git bisect good 1684096b1ed813f621fb6cbd06e72235c1c2a0ca
> > > # bad: [9c35baf6cee9a5745d55de6f9995916dde642517] Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk
> > > git bisect bad 9c35baf6cee9a5745d55de6f9995916dde642517
> > > # bad: [666e5a406c3ed562e7b3ceff8b631b6067bdaead] mm: make ttu's return boolean
> > > git bisect bad 666e5a406c3ed562e7b3ceff8b631b6067bdaead
> > > # good: [a6ffdc07847e74cc244c02ab6d0351a4a5d77281] mm: use is_migrate_highatomic() to simplify the code
> > > git bisect good a6ffdc07847e74cc244c02ab6d0351a4a5d77281
> > > # bad: [2948be5acf7d798991b127ceda6eea13e52c597f] mm: do not use double negation for testing page flags
> > > git bisect bad 2948be5acf7d798991b127ceda6eea13e52c597f
> > > # good: [9070733b4efac4bf17f299a81b01c15e206f9ff5] xfs: abstract PF_FSTRANS to PF_MEMALLOC_NOFS
> > > git bisect good 9070733b4efac4bf17f299a81b01c15e206f9ff5
> > > # bad: [81378da64de6d33d0c200885f1de431c9a3e5ccd] jbd2: mark the transaction context with the scope GFP_NOFS context
> > > git bisect bad 81378da64de6d33d0c200885f1de431c9a3e5ccd
> > > # good: [9ba1fb2c602a6f2323e3a08ec8e7a8e33bf335f4] xfs: use memalloc_nofs_{save,restore} instead of memalloc_noio*
> > > git bisect good 9ba1fb2c602a6f2323e3a08ec8e7a8e33bf335f4
> > > # first bad commit: [81378da64de6d33d0c200885f1de431c9a3e5ccd] jbd2: mark the transaction context with the scope GFP_NOFS context
> > 
> > 
> > -- 
> > Michal Hocko
> > SUSE Labs
> 
> -- 
> Michal Hocko
> SUSE Labs
> --
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