KCSAN: data-race in ext4_sync_file / writeback_single_inode (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 98477740 Merge branch 'rcu/urgent' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=165770d3900000
kernel config: https://syzkaller.appspot.com/x/.config?x=7b00edac59eadd4a
dashboard link: https://syzkaller.appspot.com/bug?extid=7e1bab882548e4db2a89
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
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+7e1bab...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in ext4_sync_file / writeback_single_inode

write to 0xffff88811eb87180 of 8 bytes by task 31753 on cpu 1:
writeback_single_inode+0x102/0x580 fs/fs-writeback.c:1567
sync_inode fs/fs-writeback.c:2605 [inline]
sync_inode_metadata+0x52/0x70 fs/fs-writeback.c:2625
ext4_fsync_nojournal fs/ext4/fsync.c:92 [inline]
ext4_sync_file+0x335/0x6e0 fs/ext4/fsync.c:170
vfs_fsync_range+0x107/0x120 fs/sync.c:200
generic_write_sync include/linux/fs.h:2747 [inline]
ext4_buffered_write_iter+0x369/0x3b0 fs/ext4/file.c:276
ext4_file_write_iter+0x768/0x1060 include/linux/fs.h:784
call_write_iter include/linux/fs.h:1882 [inline]
do_iter_readv_writev+0x32e/0x3d0 fs/read_write.c:713
do_iter_write+0x112/0x4b0 fs/read_write.c:1018
vfs_iter_write+0x4c/0x70 fs/read_write.c:1059
iter_file_splice_write+0x41a/0x770 fs/splice.c:750
do_splice_from fs/splice.c:846 [inline]
direct_splice_actor+0x95/0x160 fs/splice.c:1016
splice_direct_to_actor+0x365/0x660 fs/splice.c:971
do_splice_direct+0xf2/0x170 fs/splice.c:1059
do_sendfile+0x56a/0xba0 fs/read_write.c:1540
__do_sys_sendfile64 fs/read_write.c:1595 [inline]
__se_sys_sendfile64 fs/read_write.c:1587 [inline]
__x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1587
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88811eb87180 of 8 bytes by task 31765 on cpu 0:
ext4_fsync_nojournal fs/ext4/fsync.c:87 [inline]
ext4_sync_file+0x26c/0x6e0 fs/ext4/fsync.c:170
vfs_fsync_range+0x107/0x120 fs/sync.c:200
generic_write_sync include/linux/fs.h:2747 [inline]
ext4_buffered_write_iter+0x369/0x3b0 fs/ext4/file.c:276
ext4_file_write_iter+0x768/0x1060 include/linux/fs.h:784
call_write_iter include/linux/fs.h:1882 [inline]
do_iter_readv_writev+0x32e/0x3d0 fs/read_write.c:713
do_iter_write+0x112/0x4b0 fs/read_write.c:1018
vfs_iter_write+0x4c/0x70 fs/read_write.c:1059
iter_file_splice_write+0x41a/0x770 fs/splice.c:750
do_splice_from fs/splice.c:846 [inline]
direct_splice_actor+0x95/0x160 fs/splice.c:1016
splice_direct_to_actor+0x365/0x660 fs/splice.c:971
do_splice_direct+0xf2/0x170 fs/splice.c:1059
do_sendfile+0x56a/0xba0 fs/read_write.c:1540
__do_sys_sendfile64 fs/read_write.c:1595 [inline]
__se_sys_sendfile64 fs/read_write.c:1587 [inline]
__x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1587
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: 0 PID: 31765 Comm: syz-executor.1 Not tainted 5.9.0-rc6-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.