KCSAN: data-race in _find_next_bit / ext4_free_inode

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6799d4f2 Merge tag 'scsi-fixes' of git://git.kernel.org/pu..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=142e4a3dd00000
kernel config: https://syzkaller.appspot.com/x/.config?x=263e28245b31ec8e
dashboard link: https://syzkaller.appspot.com/bug?extid=9e944794bbb2d8a4ff2f
compiler: Debian clang version 11.0.1-2
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+9e9447...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in _find_next_bit / ext4_free_inode

write to 0xffff8881054502c8 of 8 bytes by task 1763 on cpu 0:
instrument_write include/linux/instrumented.h:42 [inline]
__instrument_read_write_bitop include/asm-generic/bitops/instrumented-non-atomic.h:79 [inline]
__test_and_clear_bit include/asm-generic/bitops/instrumented-non-atomic.h:109 [inline]
__test_and_clear_bit_le include/asm-generic/bitops/le.h:125 [inline]
ext4_free_inode+0x5ce/0xa00 fs/ext4/ialloc.c:314
ext4_evict_inode+0xb7e/0xdb0 fs/ext4/inode.c:333
evict+0x1c8/0x3c0 fs/inode.c:584
iput_final fs/inode.c:1660 [inline]
iput+0x433/0x590 fs/inode.c:1686
dentry_unlink_inode+0x23a/0x260 fs/dcache.c:376
d_delete+0x78/0xe0 fs/dcache.c:2505
vfs_rmdir+0x2a6/0x2c0 fs/namei.c:3909
do_rmdir+0x14a/0x2e0 fs/namei.c:3958
__do_sys_rmdir fs/namei.c:3976 [inline]
__se_sys_rmdir fs/namei.c:3974 [inline]
__x64_sys_rmdir+0x2c/0x30 fs/namei.c:3974
do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881054502c8 of 8 bytes by task 5819 on cpu 1:
_find_next_bit+0x4f/0x190 lib/find_bit.c:41
find_next_zero_bit include/asm-generic/bitops/find.h:94 [inline]
find_next_zero_bit_le include/asm-generic/bitops/le.h:17 [inline]
find_inode_bit+0xc8/0x330 fs/ext4/ialloc.c:722
__ext4_new_inode+0xc7a/0x2f70 fs/ext4/ialloc.c:1063
ext4_symlink+0x2c3/0x700 fs/ext4/namei.c:3463
vfs_symlink+0x23a/0x300 fs/namei.c:4172
do_symlinkat+0xeb/0x280 fs/namei.c:4202
__do_sys_symlink fs/namei.c:4223 [inline]
__se_sys_symlink fs/namei.c:4221 [inline]
__x64_sys_symlink+0x32/0x40 fs/namei.c:4221
do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000800000000ff -> 0x00000800000000df

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 5819 Comm: syz-executor.0 Not tainted 5.13.0-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.