KCSAN: data-race in __filemap_fdatawrite_range / __xa_set_mark (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e87297fa Merge tag 'drm-fixes-2020-12-04' of git://anongit..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16933373500000
kernel config: https://syzkaller.appspot.com/x/.config?x=c949fed53798f819
dashboard link: https://syzkaller.appspot.com/bug?extid=38c449cb9bb12aa90eaf
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+38c449...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __filemap_fdatawrite_range / __xa_set_mark

write to 0xffff88814062197c of 4 bytes by task 8085 on cpu 1:
xa_mark_set lib/xarray.c:69 [inline]
xas_set_mark lib/xarray.c:889 [inline]
__xa_set_mark+0x187/0x1b0 lib/xarray.c:1898
__set_page_dirty+0x17e/0x1d0 fs/buffer.c:609
mark_buffer_dirty+0x126/0x230 fs/buffer.c:1137
__ext4_handle_dirty_metadata+0x20a/0x590 fs/ext4/ext4_jbd2.c:362
ext4_do_update_inode fs/ext4/inode.c:5135 [inline]
ext4_mark_iloc_dirty+0x12ed/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
generic_update_time fs/inode.c:1764 [inline]
update_time fs/inode.c:1777 [inline]
file_update_time+0x3b0/0x3f0 fs/inode.c:1992
file_modified+0x62/0x80 fs/inode.c:2015
ext4_write_checks fs/ext4/file.c:248 [inline]
ext4_buffered_write_iter+0x1f9/0x3d0 fs/ext4/file.c:265
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

read to 0xffff88814062197c of 4 bytes by task 15947 on cpu 0:
xa_marked include/linux/xarray.h:416 [inline]
mapping_tagged include/linux/fs.h:488 [inline]
__filemap_fdatawrite_range+0x11c/0x1d0 mm/filemap.c:418
__filemap_fdatawrite mm/filemap.c:430 [inline]
filemap_fdatawrite+0x22/0x30 mm/filemap.c:435
fdatawrite_one_bdev+0x28/0x30 fs/sync.c:86
iterate_bdevs+0x178/0x220 fs/block_dev.c:2144
ksys_sync+0x85/0xe0 fs/sync.c:117
__do_sys_sync+0xa/0x10 fs/sync.c:125
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: 15947 Comm: syz-executor.4 Not tainted 5.10.0-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.