The Linux Kernel/buffer uptodate
#include <linux/buffer_head.h> // BUFFER_FNS(Uptodate, uptodate) static inline int buffer_uptodate(const struct buffer_head *bh);
Returns the up-to-date flag for the given buffer head.
It's implemented as a simple macro, which just isolates a single bit from a field in the buffer_head. It has no side effects of any kind.
true, if the buffer is up to date, i.e. the data on the physical storage could be used, to read the data back in to memory.