KCSAN: data-race in __lru_cache_add / lru_add_drain_all

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 941e0d91 mm, kcsan: Instrument SLAB/SLUB free with ASSERT_..
git tree: https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=116cd70de00000
kernel config: https://syzkaller.appspot.com/x/.config?x=b313b4492ea15bae
dashboard link: https://syzkaller.appspot.com/bug?extid=85c8a31ac01e935a6cf5
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [ak...@linux-foundation.org linux-...@vger.kernel.org linu...@kvack.org el...@google.com]

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+85c8a3...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __lru_cache_add / lru_add_drain_all

write to 0xffff88812c029b60 of 1 bytes by task 10798 on cpu 0:
pagevec_add include/linux/pagevec.h:81 [inline]
__lru_cache_add+0xb8/0x1c0 mm/swap.c:410
lru_cache_add mm/swap.c:447 [inline]
lru_cache_add_active_or_unevictable+0xb0/0x1e0 mm/swap.c:477
alloc_set_pte+0x2c4/0xee0 mm/memory.c:3488
finish_fault+0xd5/0x170 mm/memory.c:3536
do_cow_fault mm/memory.c:3711 [inline]
do_fault mm/memory.c:3804 [inline]
handle_pte_fault mm/memory.c:4033 [inline]
__handle_mm_fault+0xfdd/0x2cf0 mm/memory.c:4163
handle_mm_fault+0x21c/0x540 mm/memory.c:4200
do_user_addr_fault arch/x86/mm/fault.c:1442 [inline]
do_page_fault+0x4a4/0xa52 arch/x86/mm/fault.c:1517
page_fault+0x34/0x40 arch/x86/entry/entry_64.S:1203

read to 0xffff88812c029b60 of 1 bytes by task 16768 on cpu 1:
lru_add_drain_all+0x169/0x3a0 mm/swap.c:746
invalidate_bdev+0x65/0x90 fs/block_dev.c:97
ext4_put_super+0x3c8/0x7a0 fs/ext4/super.c:1072
generic_shutdown_super+0xfa/0x270 fs/super.c:464
kill_block_super+0x58/0xa0 fs/super.c:1444
deactivate_locked_super+0x5d/0xb0 fs/super.c:335
deactivate_super fs/super.c:366 [inline]
deactivate_super+0xca/0xe0 fs/super.c:362
cleanup_mnt+0x27a/0x330 fs/namespace.c:1102
__cleanup_mnt+0x1c/0x30 fs/namespace.c:1109
task_work_run+0xf5/0x130 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_usermode_loop+0x2ae/0x2c0 arch/x86/entry/common.c:164
prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
do_syscall_64+0x36e/0x390 arch/x86/entry/common.c:304
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16768 Comm: syz-executor.2 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.