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BUG: KCSAN: data-race in blkdev_get_by_dev / blkdev_put

write to 0xffff888100473120 of 4 bytes by task 28819 on cpu 0:
 blkdev_get_by_dev+0xa26/0xca0 fs/block_dev.c:150
 blkdev_get_by_path+0x110/0x1b0 fs/block_dev.c:1298
 mount_bdev+0x47/0x290 fs/super.c:1326
 ext4_mount+0x2d/0x40 fs/ext4/super.c:6635
 legacy_get_tree+0x70/0xc0 fs/fs_context.c:610
 vfs_get_tree+0x4a/0x1a0 fs/super.c:1498
 do_new_mount fs/namespace.c:2915 [inline]
 path_mount+0x11ca/0x1d00 fs/namespace.c:3245
 do_mount fs/namespace.c:3258 [inline]
 __do_sys_mount fs/namespace.c:3466 [inline]
 __se_sys_mount+0x23d/0x2e0 fs/namespace.c:3443
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3443
 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 0xffff888100473120 of 4 bytes by task 22608 on cpu 1:
 blkdev_put+0x3b/0x4c0 fs/block_dev.c:1348
 blkdev_close+0x47/0x50 fs/block_dev.c:1403
 __fput+0x295/0x520 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0xae/0x130 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x156/0x190 kernel/entry/common.c:209
 __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+0x49/0x90 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000003 -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 22608 Comm: systemd-udevd Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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