Buffered device block
= Buffered device block
A <data structure> holding the contents of one fixed-size region of a storage device, together with its <buffer cache key>, <buffer cache validity>, modification state and lifetime information. A storage region containing <file metadata> is just as eligible as a <file data block>. The structure can survive many callers: releasing it usually makes it available for later reuse, rather than immediately deleting the cached contents.