Feature #3397
Updated by Sage Weil over 11 years ago
This will allow us to efficiently cache ENOENT for the child so that reads pass directly to the parent, without having to cache the parent data itself. With the current layering, memory pressure will push the parent data out of memory in the child's cache and it will re-check for the child object existence.
This will also let us eliminate the double-caching that goes on. Currently, both the parent and child images will cache data.
Two things to go with this:
- ObjectCacher needs to return ENOENT so that the layering logic can live above it.
- the copyup code in the WritebackHandler needs to tell the parent cache to discard the data it just copied up.