KCSAN: data-race in __writeback_single_inode / move_expired_inodes

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4df91062 mm: memcg: relayout structure mem_cgroup to avoid..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1776588d500000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9b19d1bde60f8d
dashboard link: https://syzkaller.appspot.com/bug?extid=fdd07220b75d59f85872
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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+fdd072...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __writeback_single_inode / move_expired_inodes

read-write to 0xffff88810d5f4778 of 8 bytes by task 27961 on cpu 0:
move_expired_inodes+0x1bf/0x490 fs/fs-writeback.c:1257
queue_io+0xe1/0x2b0 fs/fs-writeback.c:1304
wb_writeback+0x255/0x660 fs/fs-writeback.c:1892
wb_do_writeback+0x101/0x5d0 fs/fs-writeback.c:2039
wb_workfn+0xb8/0x410 fs/fs-writeback.c:2080
process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
worker_thread+0x635/0xb90 kernel/workqueue.c:2418
kthread+0x1fd/0x220 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffff88810d5f4778 of 8 bytes by task 5352 on cpu 1:
__writeback_single_inode+0x45/0x560 fs/fs-writeback.c:1457
writeback_single_inode+0x126/0x580 fs/fs-writeback.c:1570
sync_inode fs/fs-writeback.c:2606 [inline]
sync_inode_metadata+0x52/0x70 fs/fs-writeback.c:2626
ext4_fsync_nojournal fs/ext4/fsync.c:92 [inline]
ext4_sync_file+0x359/0x6c0 fs/ext4/fsync.c:170
vfs_fsync_range+0x107/0x120 fs/sync.c:200
generic_write_sync include/linux/fs.h:2739 [inline]
ext4_buffered_write_iter+0x384/0x3d0 fs/ext4/file.c:278
ext4_file_write_iter+0x45e/0x1090 fs/ext4/file.c:503
call_write_iter include/linux/fs.h:1903 [inline]
do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
do_iter_write+0x112/0x4b0 fs/read_write.c:866
vfs_iter_write+0x4c/0x70 fs/read_write.c:907
iter_file_splice_write+0x42a/0x780 fs/splice.c:686
do_splice_from fs/splice.c:764 [inline]
direct_splice_actor+0x80/0xa0 fs/splice.c:933
splice_direct_to_actor+0x345/0x650 fs/splice.c:888
do_splice_direct+0xf5/0x170 fs/splice.c:976
do_sendfile+0x5db/0xca0 fs/read_write.c:1257
__do_sys_sendfile64 fs/read_write.c:1318 [inline]
__se_sys_sendfile64 fs/read_write.c:1304 [inline]
__x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1304
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 5352 Comm: syz-executor.0 Not tainted 5.10.0-rc5-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.