KCSAN: data-race in ext4_mb_regular_allocator / mb_free_blocks

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fc3abb53 Merge branch 'for-linus' of git://git.kernel.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=153826d1900000
kernel config: https://syzkaller.appspot.com/x/.config?x=8b13025dd241bdba
dashboard link: https://syzkaller.appspot.com/bug?extid=e650b68cb43c23ec0163
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+e650b6...@syzkaller.appspotmail.com

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

write to 0xffff888129eb3884 of 4 bytes by task 8727 on cpu 1:
mb_free_blocks+0x152/0xfa0 fs/ext4/mballoc.c:1492
ext4_free_blocks+0xfdc/0x18c0 fs/ext4/mballoc.c:5291
ext4_remove_blocks+0x5a7/0xa50 fs/ext4/extents.c:2497
ext4_ext_rm_leaf+0x563/0xe80 fs/ext4/extents.c:2663
ext4_ext_remove_space+0x8c9/0x14a0 fs/ext4/extents.c:2911
ext4_ext_truncate+0xf9/0x160 fs/ext4/extents.c:4371
ext4_truncate+0x889/0xc20 fs/ext4/inode.c:4216
ext4_evict_inode+0x9cf/0xc20 fs/ext4/inode.c:280
evict+0x19f/0x470 fs/inode.c:576
iput_final fs/inode.c:1652 [inline]
iput+0x44a/0x550 fs/inode.c:1678
dentry_unlink_inode+0x210/0x220 fs/dcache.c:374
d_delete+0x78/0xa0 fs/dcache.c:2470
vfs_rmdir+0x284/0x2a0 fs/namei.c:3726
do_rmdir+0x16e/0x300 fs/namei.c:3773
__do_sys_rmdir fs/namei.c:3791 [inline]
__se_sys_rmdir fs/namei.c:3789 [inline]
__x64_sys_rmdir+0x2c/0x30 fs/namei.c:3789
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888129eb3884 of 4 bytes by task 8719 on cpu 0:
ext4_mb_good_group_nolock fs/ext4/mballoc.c:2180 [inline]
ext4_mb_regular_allocator+0x866/0x18e0 fs/ext4/mballoc.c:2413
ext4_mb_new_blocks+0x304/0xcf0 fs/ext4/mballoc.c:4920
ext4_ext_map_blocks+0x164e/0x20c0 fs/ext4/extents.c:4238
ext4_map_blocks+0x6bf/0xf40 fs/ext4/inode.c:625
ext4_getblk+0x67/0x2e0 fs/ext4/inode.c:832
ext4_bread+0x3a/0x1f0 fs/ext4/inode.c:882
ext4_append+0xda/0x1c0 fs/ext4/namei.c:67
ext4_init_new_dir fs/ext4/namei.c:2765 [inline]
ext4_mkdir+0x4b6/0xc90 fs/ext4/namei.c:2810
vfs_mkdir+0x288/0x350 fs/namei.c:3649
do_mkdirat+0x132/0x220 fs/namei.c:3672
__do_sys_mkdir fs/namei.c:3688 [inline]
__se_sys_mkdir fs/namei.c:3686 [inline]
__x64_sys_mkdir+0x32/0x40 fs/namei.c:3686
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: 8719 Comm: syz-executor.1 Not tainted 5.9.0-rc3-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.