kho: make radix max key width more obvious

The KHO radix tree constants are somewhat hard to understand. The tree
depth essentially comes from the max key width. The max key width comes
from the need to store a 52-bit PFN plus one more bit for the order.

All this is very obscure with the corrent code. The PFN width is defined
as KHO_ORDER_0_LOG2, which makes very little sense to a new reader not
already familiar with what the value means. Then the fact that an extra
bit is needed is hidden in the KHO_TREE_MAX_DEPTH calculation.

Simplify this by removing KHO_ORDER_0_LOG2 and replace it with
KHO_RADIX_KEY_WIDTH. Update the comment to explain why this value is
used. This moves the +1 from KHO_TREE_MAX_DEPTH to KHO_RADIX_KEY_WIDTH,
making things clearer.

Update kho_{encode,decode}_radix_key() to not use KHO_ORDER_0_LOG2.
Instead, refactor the code and comments to make it clearer how the
encoding and decoding is done.

In kho_encode_radix_key(), add a new variable for the shift for physical
address. Use that in calculating where the order bit goes and in
calculating the shifted PFN. Update comments to make this clearer.

In kho_radix_decode_key(), turn order_bit to 0-indexed to simplify the
eventual calculation for order. Touch up comments to make the
computation clearer.

Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Link: https://patch.msgid.link/20260801084833.1897543-3-pratyush@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

0 files changed, 0 insertions, 0 deletions