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BUG: KCSAN: data-race in __blkdev_get / __blkdev_put

read-write to 0xffff888101a366e0 of 4 bytes by task 16500 on cpu 1:
 __blkdev_get+0x87/0x5b0 fs/block_dev.c:1338
 blkdev_get_by_dev+0x103/0x490 fs/block_dev.c:1437
 blkdev_open+0xa8/0x130 fs/block_dev.c:1534
 do_dentry_open+0x520/0x870 fs/open.c:817
 vfs_open+0x43/0x50 fs/open.c:931
 do_open fs/namei.c:3254 [inline]
 path_openat+0x1844/0x20a0 fs/namei.c:3371
 do_filp_open+0xbd/0x1d0 fs/namei.c:3398
 do_sys_openat2+0xa3/0x240 fs/open.c:1172
 do_sys_open fs/open.c:1188 [inline]
 __do_sys_open fs/open.c:1196 [inline]
 __se_sys_open fs/open.c:1192 [inline]
 __x64_sys_open+0xe2/0x110 fs/open.c:1192
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888101a366e0 of 4 bytes by task 8474 on cpu 0:
 __blkdev_put+0x5a/0x450 fs/block_dev.c:1554
 blkdev_put+0x212/0x290 fs/block_dev.c:1624
 blkdev_close+0x47/0x50 fs/block_dev.c:1632
 __fput+0x24b/0x4e0 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0x8e/0x110 kernel/task_work.c:140
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
 exit_to_user_mode_prepare+0x16b/0x1a0 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:302
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8474 Comm: syz-executor.2 Not tainted 5.11.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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