bdflush — start, flush, or tune buffer-dirty-flush daemon
#include <sys/kdaemon.h>
int
bdflush( |
int | func, |
| long * | address); |
int
bdflush( |
int | func, |
| long | data); |
bdflush() starts, flushes,
or tunes the buffer-dirty-flush daemon. Only a privileged
process (one with the CAP_SYS_ADMIN capability) may call
bdflush().
If func is
negative or 0, and no daemon has been started, then
bdflush() enters the daemon
code and never returns.
If func is 1, some
dirty buffers are written to disk.
If func is 2 or
more and is even (low bit is 0), then address is the address of a
long word, and the tuning parameter numbered (func−2)/2 is returned to
the caller in that address.
If func is 3 or
more and is odd (low bit is 1), then data is a long word, and the
kernel sets tuning parameter numbered (func−3)/2 to that
value.
The set of parameters, their values, and their legal
ranges are defined in the kernel source file fs/buffer.c.
If func is
negative or 0 and the daemon successfully starts,
bdflush() never returns.
Otherwise, the return value is 0 on success and −1 on
failure, with errno set to
indicate the error.
An attempt was made to enter the daemon code after another process has already entered.
address
points outside your accessible address space.
An attempt was made to read or write an invalid parameter number, or to write an invalid value to a parameter.
Caller does not have the CAP_SYS_ADMIN capability.
bdflush() is Linux-specific
and should not be used in programs intended to be
portable.