kernel BUG at mm/internal.h:LINE!

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    a5ed1e96 Merge tag 'powerpc-5.1-3' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=117a556d200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9a31fb246de2a622
dashboard link: https://syzkaller.appspot.com/bug?extid=ce4fa49466985039fb35
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+ce4fa49466985039fb35@xxxxxxxxxxxxxxxxxxxxxxxxx

page:ffffea0002fffa00 count:2 mapcount:1 mapping:ffff8880970929f0  
index:0x4e4
ext4_da_aops
name:"syz-fuzzer"
flags: 0x1fffc0000020016(referenced|uptodate|lru|mappedtodisk)
raw: 01fffc0000020016 ffffea0001f82548 ffffea0001ab5388 ffff8880970929f0
raw: 00000000000004e4 0000000000000000 0000000200000000 ffff8880aa204bc0
page dumped because: VM_BUG_ON_PAGE(page_ref_count(page))
page->mem_cgroup:ffff8880aa204bc0
------------[ cut here ]------------
kernel BUG at mm/internal.h:77!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 1046 Comm: kcompactd0 Not tainted 5.1.0-rc1+ #34
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:set_page_refcounted mm/internal.h:77 [inline]
RIP: 0010:set_page_refcounted mm/internal.h:74 [inline]
RIP: 0010:split_page+0x1e5/0x250 mm/page_alloc.c:2999
Code: 4c 89 e7 e8 5d 98 0c 00 0f 0b 48 c7 c6 20 09 72 87 4c 89 e7 e8 4c 98  
0c 00 0f 0b 48 c7 c6 a0 09 72 87 4c 89 e7 e8 3b 98 0c 00 <0f> 0b 48 c7 c6  
c0 08 72 87 4c 89 e7 e8 2a 98 0c 00 0f 0b 4c 89 f7
RSP: 0000:ffff8880a83d77b8 EFLAGS: 00010293
RAX: ffff8880a83c80c0 RBX: ffffea0002fffa34 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8199dda2 RDI: ffffed101507aedb
RBP: ffff8880a83d77d8 R08: 0000000000000021 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffea0002fffa00
R13: dffffc0000000000 R14: ffffea0003000034 R15: ffffea0002fff800
FS:  0000000000000000(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f161d6cc169 CR3: 0000000095b2c000 CR4: 00000000001426e0
Call Trace:
 split_map_pages+0x334/0x540 mm/compaction.c:83
 isolate_freepages mm/compaction.c:1529 [inline]
 compaction_alloc+0x14ca/0x2290 mm/compaction.c:1543
 unmap_and_move mm/migrate.c:1175 [inline]
 migrate_pages+0x484/0x2cd0 mm/migrate.c:1426
 compact_zone+0x1b56/0x38d0 mm/compaction.c:2174
 kcompactd_do_work+0x303/0xaa0 mm/compaction.c:2555
 kcompactd+0x247/0x890 mm/compaction.c:2648
 kthread+0x357/0x430 kernel/kthread.c:253
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Modules linked in:
---[ end trace c8941b63dcddd106 ]---
RIP: 0010:set_page_refcounted mm/internal.h:77 [inline]
RIP: 0010:set_page_refcounted mm/internal.h:74 [inline]
RIP: 0010:split_page+0x1e5/0x250 mm/page_alloc.c:2999
Code: 4c 89 e7 e8 5d 98 0c 00 0f 0b 48 c7 c6 20 09 72 87 4c 89 e7 e8 4c 98  
0c 00 0f 0b 48 c7 c6 a0 09 72 87 4c 89 e7 e8 3b 98 0c 00 <0f> 0b 48 c7 c6  
c0 08 72 87 4c 89 e7 e8 2a 98 0c 00 0f 0b 4c 89 f7
RSP: 0000:ffff8880a83d77b8 EFLAGS: 00010293
RAX: ffff8880a83c80c0 RBX: ffffea0002fffa34 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8199dda2 RDI: ffffed101507aedb
RBP: ffff8880a83d77d8 R08: 0000000000000021 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffea0002fffa00
R13: dffffc0000000000 R14: ffffea0003000034 R15: ffffea0002fff800
FS:  0000000000000000(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000422d10 CR3: 0000000095b2c000 CR4: 00000000001426e0


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