KCSAN: data-race in generic_write_end / mpage_submit_page (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: a6311db0 x86, kcsan: Enable KCSAN for x86
git tree: https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=178fcacf600000
kernel config: https://syzkaller.appspot.com/x/.config?x=87d111955f40591f
dashboard link: https://syzkaller.appspot.com/bug?extid=29a42d94d01cf2721f04
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [adilger...@dilger.ca linux...@vger.kernel.org
linux-...@vger.kernel.org ty...@mit.edu el...@google.com]

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+29a42d...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in generic_write_end / mpage_submit_page

read to 0xffff888125d507a8 of 8 bytes by task 24 on cpu 1:
mpage_submit_page+0x81/0x170 fs/ext4/inode.c:2216
mpage_map_and_submit_buffers+0x331/0x520 fs/ext4/inode.c:2422
mpage_map_and_submit_extent fs/ext4/inode.c:2556 [inline]
ext4_writepages+0x1458/0x2300 fs/ext4/inode.c:2869
do_writepages+0x6b/0x170 mm/page-writeback.c:2344
__writeback_single_inode+0xaf/0x8e0 fs/fs-writeback.c:1449
writeback_sb_inodes+0x4ba/0xa50 fs/fs-writeback.c:1713
__writeback_inodes_wb+0xe8/0x1b0 fs/fs-writeback.c:1782
wb_writeback+0x557/0x6a0 fs/fs-writeback.c:1891
wb_check_background_flush fs/fs-writeback.c:1959 [inline]
wb_do_writeback fs/fs-writeback.c:2047 [inline]
wb_workfn+0x696/0x970 fs/fs-writeback.c:2075
process_one_work+0x3d4/0x890 kernel/workqueue.c:2269
worker_thread+0xa0/0x800 kernel/workqueue.c:2415
kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

write to 0xffff888125d507a8 of 8 bytes by task 7962 on cpu 0:
i_size_write include/linux/fs.h:888 [inline]
generic_write_end+0xd0/0x1f0 fs/buffer.c:2143
ext4_da_write_end+0x158/0x620 fs/ext4/inode.c:3189
generic_perform_write+0x1d3/0x320 mm/filemap.c:3315
__generic_file_write_iter+0x251/0x380 mm/filemap.c:3433
ext4_file_write_iter+0x1bd/0xa00 fs/ext4/file.c:268
call_write_iter include/linux/fs.h:1895 [inline]
new_sync_write+0x388/0x4a0 fs/read_write.c:483
__vfs_write+0xb1/0xc0 fs/read_write.c:496
vfs_write fs/read_write.c:558 [inline]
vfs_write+0x18a/0x390 fs/read_write.c:542
ksys_write+0xd5/0x1b0 fs/read_write.c:611
__do_sys_write fs/read_write.c:623 [inline]
__se_sys_write fs/read_write.c:620 [inline]
__x64_sys_write+0x4c/0x60 fs/read_write.c:620
do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7962 Comm: syz-executor.4 Not tainted 5.4.0-rc3+ #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.