Working with the Unix OS

Buffer Cache
The kernel places the buffer at the end of the free list, unless an I/O error occurred or is marked old, in which case it places the buffer at the beginning of the free list.
The kernel raises the processor execution level to prevent disk interrupts while manipulating the free list, thereby preventing corruption of the buffer pointers.
Figure 67. Second
Scenario for Buffer
Allocation
When the
asynchronous write
completes, the
kernel releases the
buffer and places it
at the head of the
free list.
Figure 68. Third
Scenario for Buffer
Allocation
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