KCSAN: data-race in write_cache_pages / write_cache_pages (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4429f14a Merge tag 'block-5.10-2020-11-07' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=146edd46500000
kernel config: https://syzkaller.appspot.com/x/.config?x=76dfc991796328d4
dashboard link: https://syzkaller.appspot.com/bug?extid=e3619e90dd0dbd9f431d
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [ak...@linux-foundation.org linux-...@vger.kernel.org linu...@kvack.org]

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e3619e...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in write_cache_pages / write_cache_pages

write to 0xffff8881404659e0 of 8 bytes by task 8479 on cpu 0:
write_cache_pages+0x7ab/0x7f0 mm/page-writeback.c:2297
generic_writepages+0x64/0xa0 mm/page-writeback.c:2337
blkdev_writepages+0x19/0x20 fs/block_dev.c:1946
do_writepages+0x7b/0x150 mm/page-writeback.c:2352
__filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:422
filemap_write_and_wait_range+0x8b/0x2a0 mm/filemap.c:655
filemap_write_and_wait include/linux/fs.h:2633 [inline]
__sync_blockdev+0x51/0x70 fs/block_dev.c:509
__sync_filesystem fs/sync.c:40 [inline]
sync_filesystem+0x135/0x160 fs/sync.c:67
ovl_sync_fs+0x94/0xc0 fs/overlayfs/super.c:283
__sync_filesystem fs/sync.c:39 [inline]
sync_filesystem+0x112/0x160 fs/sync.c:67
generic_shutdown_super+0x3c/0x1f0 fs/super.c:448
kill_anon_super+0x23/0x40 fs/super.c:1108
deactivate_locked_super+0x6a/0xb0 fs/super.c:335
deactivate_super+0x85/0x90 fs/super.c:366
cleanup_mnt+0x277/0x2e0 fs/namespace.c:1118
__cleanup_mnt+0x15/0x20 fs/namespace.c:1125
task_work_run+0x8e/0x110 kernel/task_work.c:151
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_user_mode_loop kernel/entry/common.c:164 [inline]
exit_to_user_mode_prepare+0x13c/0x170 kernel/entry/common.c:191
syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:266
do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8881404659e0 of 8 bytes by task 8473 on cpu 1:
write_cache_pages+0x7ab/0x7f0 mm/page-writeback.c:2297
generic_writepages+0x64/0xa0 mm/page-writeback.c:2337
blkdev_writepages+0x19/0x20 fs/block_dev.c:1946
do_writepages+0x7b/0x150 mm/page-writeback.c:2352
__filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:422
__filemap_fdatawrite mm/filemap.c:430 [inline]
filemap_flush+0x1f/0x30 mm/filemap.c:457
__sync_blockdev+0x69/0x70 fs/block_dev.c:508
__sync_filesystem fs/sync.c:40 [inline]
sync_filesystem+0xcb/0x160 fs/sync.c:64
ovl_sync_fs+0x94/0xc0 fs/overlayfs/super.c:283
__sync_filesystem fs/sync.c:39 [inline]
sync_filesystem+0x112/0x160 fs/sync.c:67
generic_shutdown_super+0x3c/0x1f0 fs/super.c:448
kill_anon_super+0x23/0x40 fs/super.c:1108
deactivate_locked_super+0x6a/0xb0 fs/super.c:335
deactivate_super+0x85/0x90 fs/super.c:366
cleanup_mnt+0x277/0x2e0 fs/namespace.c:1118
__cleanup_mnt+0x15/0x20 fs/namespace.c:1125
task_work_run+0x8e/0x110 kernel/task_work.c:151
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_user_mode_loop kernel/entry/common.c:164 [inline]
exit_to_user_mode_prepare+0x13c/0x170 kernel/entry/common.c:191
syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:266
do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 8473 Comm: syz-executor.0 Not tainted 5.10.0-rc2-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.