KCSAN: data-race in ext4_mb_regular_allocator / mb_mark_used

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6ba1b005 Merge tag 'asm-generic-fixes-5.8' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15e8e774900000
kernel config: https://syzkaller.appspot.com/x/.config?x=fb2adeb558c16fc1
dashboard link: https://syzkaller.appspot.com/bug?extid=14b716e569456dfb95c3
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
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+14b716...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in ext4_mb_regular_allocator / mb_mark_used

write to 0xffff88821aad9014 of 4 bytes by task 24284 on cpu 1:
mb_mark_used+0x135/0xba0 fs/ext4/mballoc.c:1637
ext4_mb_use_best_found+0x102/0x2f0 fs/ext4/mballoc.c:1708
ext4_mb_measure_extent fs/ext4/mballoc.c:1827 [inline]
ext4_mb_complex_scan_group+0x345/0x820 fs/ext4/mballoc.c:2058
ext4_mb_regular_allocator+0xcda/0xfe0 fs/ext4/mballoc.c:2328
ext4_mb_new_blocks+0x304/0xcf0 fs/ext4/mballoc.c:4721
ext4_new_meta_blocks+0x84/0x180 fs/ext4/balloc.c:667
ext4_ext_grow_indepth fs/ext4/extents.c:1282 [inline]
ext4_ext_create_new_leaf fs/ext4/extents.c:1386 [inline]
ext4_ext_insert_extent+0x9b3/0x2b80 fs/ext4/extents.c:2059
ext4_split_extent_at+0x6cb/0xb10 fs/ext4/extents.c:3213
ext4_force_split_extent_at fs/ext4/extents.c:305 [inline]
ext4_swap_extents+0xd35/0x1330 fs/ext4/extents.c:5655
move_extent_per_page+0x131a/0x1560 fs/ext4/move_extent.c:339
ext4_move_extents+0xa98/0xbe0 fs/ext4/move_extent.c:673
ext4_ioctl+0x2051/0x3920 fs/ext4/ioctl.c:986
vfs_ioctl fs/ioctl.c:48 [inline]
ksys_ioctl fs/ioctl.c:753 [inline]
__do_sys_ioctl fs/ioctl.c:762 [inline]
__se_sys_ioctl+0xc9/0x130 fs/ioctl.c:760
__x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:760
do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88821aad9014 of 4 bytes by task 24278 on cpu 0:
ext4_mb_good_group_nolock fs/ext4/mballoc.c:2186 [inline]
ext4_mb_regular_allocator+0x6f9/0xfe0 fs/ext4/mballoc.c:2297
ext4_mb_new_blocks+0x304/0xcf0 fs/ext4/mballoc.c:4721
ext4_new_meta_blocks+0x84/0x180 fs/ext4/balloc.c:667
ext4_ext_grow_indepth fs/ext4/extents.c:1282 [inline]
ext4_ext_create_new_leaf fs/ext4/extents.c:1386 [inline]
ext4_ext_insert_extent+0x9b3/0x2b80 fs/ext4/extents.c:2059
ext4_split_extent_at+0x6cb/0xb10 fs/ext4/extents.c:3213
ext4_force_split_extent_at fs/ext4/extents.c:305 [inline]
ext4_swap_extents+0xd35/0x1330 fs/ext4/extents.c:5655
move_extent_per_page+0x131a/0x1560 fs/ext4/move_extent.c:339
ext4_move_extents+0xa98/0xbe0 fs/ext4/move_extent.c:673
ext4_ioctl+0x2051/0x3920 fs/ext4/ioctl.c:986
vfs_ioctl fs/ioctl.c:48 [inline]
ksys_ioctl fs/ioctl.c:753 [inline]
__do_sys_ioctl fs/ioctl.c:762 [inline]
__se_sys_ioctl+0xc9/0x130 fs/ioctl.c:760
__x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:760
do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 24278 Comm: syz-executor.4 Not tainted 5.8.0-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.