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       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);


       Note: Since Linux 2.6, this system call is deprecated and does nothing.
       It is likely to  disappear  altogether  in  a  future  kernel  release.
       Nowadays,  the  task  performed  by  bdflush() is handled by the kernel
       pdflush thread.

       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

       The set of parameters, their values, and their valid ranges are defined
       in the Linux 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.


       EBUSY  An attempt was made to  enter  the  daemon  code  after  another
              process has already entered.

       EFAULT address points outside your accessible address space.

       EINVAL An  attempt  was  made  to  read  or  write an invalid parameter
              number, or to write an invalid value to a parameter.

       EPERM  Caller does not have the CAP_SYS_ADMIN capability.


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


       fsync(2), sync(2), sync(1)


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