KCSAN: data-race in ext4_ext_try_to_merge_right / ext4_mark_iloc_dirty (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 251a1524293d Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14706552300000
kernel config: https://syzkaller.appspot.com/x/.config?x=325496b7f882bca
dashboard link: https://syzkaller.appspot.com/bug?extid=cd913418a33c853906a1
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
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+cd9134...@syzkaller.appspotmail.com

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

write to 0xffff8881066b35cc of 2 bytes by task 1795 on cpu 1:
ext4_ext_try_to_merge_right+0x285/0x4c0 fs/ext4/extents.c:1772
ext4_ext_try_to_merge+0x6b/0x310 fs/ext4/extents.c:1856
ext4_convert_unwritten_extents_endio fs/ext4/extents.c:3728 [inline]
ext4_ext_handle_unwritten_extents+0x67a/0xaa0 fs/ext4/extents.c:3856
ext4_ext_map_blocks+0x719/0x1f00 fs/ext4/extents.c:4126
ext4_map_blocks+0x70d/0xef0 fs/ext4/inode.c:638
ext4_convert_unwritten_extents+0x15a/0x2c0 fs/ext4/extents.c:4767
ext4_convert_unwritten_io_end_vec+0xa4/0x130 fs/ext4/extents.c:4806
ext4_end_io_end fs/ext4/page-io.c:184 [inline]
ext4_do_flush_completed_IO fs/ext4/page-io.c:257 [inline]
ext4_end_io_rsv_work+0x198/0x360 fs/ext4/page-io.c:271
process_one_work+0x3e9/0x8f0 kernel/workqueue.c:2276
worker_thread+0x636/0xae0 kernel/workqueue.c:2422
kthread+0x262/0x280 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

read to 0xffff8881066b35cc of 4 bytes by task 12298 on cpu 0:
ext4_do_update_inode fs/ext4/inode.c:5109 [inline]
ext4_mark_iloc_dirty+0xd69/0x1750 fs/ext4/inode.c:5724
__ext4_mark_inode_dirty+0x4db/0x5b0 fs/ext4/inode.c:5918
ext4_dirty_inode+0x86/0xa0 fs/ext4/inode.c:5947
__mark_inode_dirty+0x77/0x680 fs/fs-writeback.c:2398
mark_inode_dirty include/linux/fs.h:2403 [inline]
generic_write_end+0x157/0x180 fs/buffer.c:2198
ext4_da_write_end+0x59b/0x730 fs/ext4/inode.c:3110
generic_perform_write+0x22a/0x3c0 mm/filemap.c:3667
ext4_buffered_write_iter+0x2f2/0x3f0 fs/ext4/file.c:269
ext4_file_write_iter+0x2e7/0x11d0 fs/ext4/file.c:519
call_write_iter include/linux/fs.h:2114 [inline]
do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
do_iter_write+0x112/0x4c0 fs/read_write.c:866
vfs_iter_write+0x4c/0x70 fs/read_write.c:907
iter_file_splice_write+0x40a/0x750 fs/splice.c:689
do_splice_from fs/splice.c:767 [inline]
direct_splice_actor+0x80/0xa0 fs/splice.c:936
splice_direct_to_actor+0x345/0x650 fs/splice.c:891
do_splice_direct+0xf5/0x170 fs/splice.c:979
do_sendfile+0x773/0xda0 fs/read_write.c:1260
__do_sys_sendfile64 fs/read_write.c:1325 [inline]
__se_sys_sendfile64 fs/read_write.c:1311 [inline]
__x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1311
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x000005d0 -> 0x000005e0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12298 Comm: syz-executor.1 Tainted: G W 5.14.0-rc4-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.