KCSAN: data-race in ext4_ext_try_to_merge_right / ext4_mark_iloc_dirty (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0477e928 Linux 5.10-rc7
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=177880bd500000
kernel config: https://syzkaller.appspot.com/x/.config?x=329e76890d0bf5c3
dashboard link: https://syzkaller.appspot.com/bug?extid=b25577317f3a110ab13e
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [adilger...@dilger.ca linux...@vger.kernel.org linux-...@vger.kernel.org ty...@mit.edu]

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+b25577...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in ext4_ext_try_to_merge_right / ext4_mark_iloc_dirty

write to 0xffff8880091db1d0 of 2 bytes by task 21586 on cpu 0:
ext4_ext_try_to_merge_right+0x285/0x4c0 fs/ext4/extents.c:1768
ext4_ext_try_to_merge+0x9b/0x310 fs/ext4/extents.c:1855
ext4_convert_unwritten_extents_endio fs/ext4/extents.c:3721 [inline]
ext4_ext_handle_unwritten_extents+0x64f/0xa90 fs/ext4/extents.c:3849
ext4_ext_map_blocks+0x728/0x1fc0 fs/ext4/extents.c:4119
ext4_map_blocks+0x700/0xfc0 fs/ext4/inode.c:628
ext4_convert_unwritten_extents+0x15a/0x2c0 fs/ext4/extents.c:4760
ext4_convert_unwritten_io_end_vec+0xa4/0x130 fs/ext4/extents.c:4799
ext4_end_io_end fs/ext4/page-io.c:187 [inline]
ext4_do_flush_completed_IO fs/ext4/page-io.c:260 [inline]
ext4_end_io_rsv_work+0x198/0x360 fs/ext4/page-io.c:274
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 0xffff8880091db1d0 of 4 bytes by task 2686 on cpu 1:
ext4_do_update_inode fs/ext4/inode.c:5105 [inline]
ext4_mark_iloc_dirty+0xd2f/0x1650 fs/ext4/inode.c:5712
__ext4_mark_inode_dirty+0x450/0x610 fs/ext4/inode.c:5906
ext4_dirty_inode+0xa6/0xc0 fs/ext4/inode.c:5942
__mark_inode_dirty+0x74/0x740 fs/fs-writeback.c:2260
mark_inode_dirty include/linux/fs.h:2183 [inline]
generic_write_end+0x15e/0x250 fs/buffer.c:2202
ext4_da_write_end+0x59b/0x760 fs/ext4/inode.c:3102
generic_perform_write+0x23e/0x3a0 mm/filemap.c:3340
ext4_buffered_write_iter+0x2e5/0x3d0 fs/ext4/file.c:270
ext4_file_write_iter+0x45e/0x1090 fs/ext4/file.c:503
call_write_iter include/linux/fs.h:1903 [inline]
new_sync_write fs/read_write.c:518 [inline]
vfs_write+0x6d4/0x7c0 fs/read_write.c:605
ksys_write+0xce/0x180 fs/read_write.c:658
__do_sys_write fs/read_write.c:670 [inline]
__se_sys_write fs/read_write.c:667 [inline]
__x64_sys_write+0x3e/0x50 fs/read_write.c:667
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: 2686 Comm: syz-executor.5 Not tainted 5.10.0-rc7-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.