I keep wanting this to use a linked-list, since I think there's
potentially some interesting use with lower layers cheaply prepending
attributes to attribute lists from upper layers. (terminating at the
user-provided custom attributes, for example). But this never really
works out.
In this case, the amount of in-place editing in B-trees just makes
maintaining the next pointers just not worth the extra code cost. And
it's likely measurements will show what was found in the original
version of v2: the RAM/code cost of next pointers outweighs any benefits
potentially gained from prepending attributes for free.
In practice, we can't really just prepend custom attributes, as this
would expose the internal lfs_attr_t struct and tag encoding to the
public API.
And you can always have in-device-only tags that are handled specially
to enable a limited form of this attribute list extension. This is how
custom attributes are currently implemented.
Christopher Haster
a463d6f106