syzbot

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BUG: KCSAN: data-race in kmmpd / mount_bdev

write to 0xffff8881392b1050 of 8 bytes by task 16833 on cpu 1:
 mount_bdev+0x240/0x290 fs/super.c:1374
 ext4_mount+0x2d/0x40 fs/ext4/super.c:6634
 legacy_get_tree+0x70/0xc0 fs/fs_context.c:592
 vfs_get_tree+0x4a/0x1a0 fs/super.c:1498
 do_new_mount fs/namespace.c:2905 [inline]
 path_mount+0x11d4/0x1ce0 fs/namespace.c:3235
 do_mount fs/namespace.c:3248 [inline]
 __do_sys_mount fs/namespace.c:3456 [inline]
 __se_sys_mount+0x23d/0x2e0 fs/namespace.c:3433
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3433
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881392b1050 of 8 bytes by task 16842 on cpu 0:
 sb_rdonly include/linux/fs.h:2220 [inline]
 kmmpd+0x2ef/0x5f0 fs/ext4/mmp.c:187
 kthread+0x262/0x280 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

value changed: 0x0000000010010000 -> 0x0000000070010000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 16842 Comm: kmmpd-loop3 Not tainted 5.13.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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