NAME

       pmem2_get_drain_fn() - get a drain function

SYNOPSIS

              #include <libpmem2.h>

              typedef void (*pmem2_drain_fn)(void);

              struct pmem2_map;

              pmem2_drain_fn pmem2_get_drain_fn(struct pmem2_map *map);

DESCRIPTION

       The  pmem2_get_drain_fn()  function  returns  a  pointer  to  a  function  responsible for
       efficiently draining flushes (see  pmem2_get_flush_fn(3))  in  the  range  owned  by  map.
       Draining,  in this context, means making sure that the flushes before this operation won't
       be reordered after it.  While it is not strictly true,  draining  can  be  thought  of  as
       waiting for previous flushes to complete.

       If  two (or more) mappings share the same drain function, it is safe to call this function
       once for all flushes belonging to those mappings.

RETURN VALUE

       The pmem2_get_drain_fn() function never returns NULL.

       The pmem2_get_drain_fn() for the same map always returns the same  function.   This  means
       that  it's  safe to cache its return value.  However, this function is very cheap (because
       it returns a precomputed value), so caching may not be necessary.

SEE ALSO

       pmem2_get_flush_fn(3),   pmem2_get_persist_fn(3),   pmem2_map_new(3),   libpmem2(7)    and
       <https://pmem.io>