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sequential_cutoff Is Missing

Symptom

If the sequential_cutoff function is missing in the official CentOS 7.6 kernel, the following information is displayed:

# echo 4M > /sys/block/bcache0/bcache/sequential_cutoff
-bash: /sys/block/bcache0/bcache/sequential_cutoff: Permission denied

Handling Procedure

The cause of this problem is that the official CentOS 7.6 kernel does not include the sequential_cutoff function. To resolve this problem, obtain the official kernel and modify the kernel configuration file.

  1. Enable the CONFIG_BCACHE macro definition.
  2. Recompile the kernel.
  3. Upgrade the kernel.
  4. Compile and install bcache. For details, see Compiling and Installing Software.
Parent topic: Troubleshooting