FYI, we noticed the following commit (built with gcc-6):

commit: 332391a9935da939319e473b4680e173df75afcf ("fs: Fix page cache inconsistency when mixing buffered and AIO DIO")
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master

in testcase: xfstests
with following parameters:

	disk: 4HDD
	fs: xfs
	test: generic-slow2

test-description: xfstests is a regression test suite for xfs and other files ystems.
test-url: git://git.kernel.org/pub/scm/fs/xfs/xfstests-dev.git


on test machine: qemu-system-x86_64 -enable-kvm -cpu qemu64,+ssse3 -smp 4 -m 4G

caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):


+-------------------------------------------------------------------+------------+------------+
|                                                                   | bb1cc74790 | 332391a993 |
+-------------------------------------------------------------------+------------+------------+
| boot_successes                                                    | 62         | 24         |
| boot_failures                                                     | 1          | 33         |
| WARNING:at_fs/btrfs/extent-tree.c:#btrfs_free_block_groups[btrfs] | 1          |            |
| WARNING:at_fs/direct-io.c:#dio_complete                           | 0          | 25         |
| WARNING:at_fs/iomap.c:#iomap_dio_complete                         | 0          | 8          |
+-------------------------------------------------------------------+------------+------------+



[  170.063040] WARNING: CPU: 0 PID: 33 at fs/iomap.c:731 iomap_dio_complete+0x129/0x130
[  170.068758] Modules linked in: xfs dm_mod rpcsec_gss_krb5 auth_rpcgss nfsv4 dns_resolver sr_mod cdrom sg ata_generic pata_acpi ppdev ata_piix parport_pc snd_pcm snd_timer snd soundcore serio_raw pcspkr i2c_piix4 libata floppy parport ip_tables
[  170.074819] CPU: 0 PID: 33 Comm: kworker/0:1 Not tainted 4.14.0-rc1-00056-g332391a #1
[  170.077915] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[  170.081047] Workqueue: dio/vda iomap_dio_complete_work
[  170.081974] task: ffff88012e504a80 task.stack: ffffc90000758000
[  170.084465] RIP: 0010:iomap_dio_complete+0x129/0x130
[  170.085381] RSP: 0018:ffffc9000075be18 EFLAGS: 00010286
[  170.087536] RAX: 00000000fffffff0 RBX: 0000000000000001 RCX: 000000000000000c
[  170.088853] RDX: 0000000000000000 RSI: ffffc9000075bc50 RDI: ffff880075715da9
[  170.092113] RBP: ffffc9000075be30 R08: ffffc9000075bcf0 R09: ffff880075715da8
[  170.093254] R10: 000000000000000c R11: 0000000000000000 R12: ffff88007afa9300
[  170.096475] R13: ffff88007ac7ad80 R14: ffff88007afa9338 R15: ffff88007afa9330
[  170.098187] FS:  0000000000000000(0000) GS:ffff88013fc00000(0000) knlGS:0000000000000000
[  170.101322] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  170.102265] CR2: 00007f3ad48a8020 CR3: 000000007fe16000 CR4: 00000000000006f0
[  170.104631] Call Trace:
[  170.105146]  iomap_dio_complete_work+0x25/0x80
[  170.106704]  process_one_work+0x198/0x3e0
[  170.107874]  worker_thread+0x4e/0x3e0
[  170.108522]  kthread+0x114/0x150
[  170.110683]  ? process_one_work+0x3e0/0x3e0
[  170.111362]  ? kthread_create_on_node+0x40/0x40
[  170.113111]  ret_from_fork+0x25/0x30
[  170.113752] Code: c9 74 17 49 63 74 24 28 41 8b 54 24 24 85 f6 0f 84 2a ff ff ff e9 3e ff ff ff 41 8b 74 24 28 49 8b 45 00 48 63 de e9 39 ff ff ff <0f> ff eb ca 0f 1f 00 0f 1f 44 00 00 55 48 83 ef 30 48 89 e5 41 
[  170.116540] ---[ end trace 23a07b952f574121 ]---


To reproduce:

        git clone https://github.com/intel/lkp-tests.git
        cd lkp-tests
        bin/lkp qemu -k <bzImage> job-script  # job-script is attached in this email



Thanks,
Xiaolong