In Ext2FSInode::compute_block_list_impl(), each call to
process_block_array() creates a new ByteBuffer, which leads to a
kmalloc() call. The ByteBuffer is then discarded when
process_block_array() exits, leading to a kfree() call.
This leads to repeated kmalloc() and kfree() calls as ByteBuffers are
created and destroyed each time process_block_array() is called.
This commit makes it so that only 1 ByteBuffer is created for each level
of inode indirect block (so only 3 ByteBuffers are created at most).
These ByteBuffers are re-used on each call to process_block_array().
This reduces the number of kmalloc() and kfree() calls during
compute_block_list_impl(), especially for larger files.
44a2157e2e