bdflush - start, flush, or tune buffer-dirty-flush daemon
int bdflush(int func, long *address);
int bdflush(int func, long data);
bdflush starts, flushes, or tunes the buffer-dirty-flush daemon. Only
the super-user 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.
EPERM Caller is not super-user.
EFAULT address points outside your accessible address space.
EBUSY An attempt was made to enter the daemon code after another
process has already entered.
EINVAL An attempt was made to read or write an invalid parameter number,
or to write an invalid value to a parameter.
bdflush is Linux specific and should not be used in programs intended
to be portable.
fsync(2), sync(2), update(8), sync(8)
Linux 1.2.4 1995-04-15 BDFLUSH(2)
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