kernel - SWAP CACHE part 19/many - distinguish bulk data in HAMMER block dev
* Add buf->flags/B_NOTMETA, vm_page->flags/PG_NOTMETA. If set the pages
underlying the buffer will not be considered meta-data from the
point of view of the swapcache.
* HAMMER must sometimes access bulk data via the block device instead of
via a file vnode. For example, the reblocking and mirroring code.
We do not want this data to be misinterpreted as meta-data when
the meta-data-only swapcache is turned on, otherwise it will blow
out the actual meta-data in the swapcache.
HAMMER_RECTYPE_DATA and HAMMER_RECTYPE_DB are considered normal data.
All other record types (e.g. direntry, inode, etc) are meta-data.