NAME

     bdflush - start, flush, or tune buffer-dirty-flush daemon

SYNOPSIS

     int bdflush(int func, long *address);
     int bdflush(int func, long data);

DESCRIPTION

     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 param-
     eter 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.

RETURN VALUE

     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.

ERRORS

     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.

CONFORMING TO

     bdflush is Linux specific and should not be used in programs
     intended to be portable.

SEE ALSO

     fsync(2), sync(2), update(8), sync(8).