KCSAN: data-race in __ext4_update_other_inode_time / d_instantiate_new

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 1127b219 Merge tag 'fallthrough-fixes-5.9-rc3' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=141ef425900000
kernel config: https://syzkaller.appspot.com/x/.config?x=8512f120b55c113f
dashboard link: https://syzkaller.appspot.com/bug?extid=18c763eeb28dd25d2d9e
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
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+18c763...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __ext4_update_other_inode_time / d_instantiate_new

write to 0xffff88808c891200 of 8 bytes by task 12782 on cpu 0:
d_instantiate_new+0x99/0xe0 fs/dcache.c:1996
ext4_add_nondir+0x172/0x1a0 fs/ext4/namei.c:2592
ext4_symlink+0x5be/0x7e0 fs/ext4/namei.c:3384
vfs_symlink+0x218/0x2d0 fs/namei.c:3959
do_symlinkat+0xee/0x280 fs/namei.c:3986
__do_sys_symlink fs/namei.c:4005 [inline]
__se_sys_symlink fs/namei.c:4003 [inline]
__x64_sys_symlink+0x32/0x40 fs/namei.c:4003
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88808c891200 of 8 bytes by task 16133 on cpu 1:
__ext4_update_other_inode_time+0x45/0x570 fs/ext4/inode.c:4893
ext4_update_other_inodes_time fs/ext4/inode.c:4940 [inline]
ext4_do_update_inode fs/ext4/inode.c:5068 [inline]
ext4_mark_iloc_dirty+0x1296/0x1660 fs/ext4/inode.c:5624
__ext4_mark_inode_dirty+0x448/0x630 fs/ext4/inode.c:5818
__ext4_new_inode+0x2a29/0x2fc0 fs/ext4/ialloc.c:1193
ext4_mkdir+0x299/0xc90 fs/ext4/namei.c:2800
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: 1 PID: 16133 Comm: syz-executor.4 Not tainted 5.9.0-rc2-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.