BDFLUSH(2)                (2016-10-08)                 BDFLUSH(2)

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

     SYNOPSIS
          #include <sys/kdaemon.h>

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

     DESCRIPTION
          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 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 valid ranges
          are defined in the Linux 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
          EBUSY
               An attempt was made to enter the daemon code after
               another process has already entered.

          EFAULT
               address points outside your accessible address space.

     Page 1                        Linux             (printed 5/24/22)

     BDFLUSH(2)                (2016-10-08)                 BDFLUSH(2)

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

          EPERM
               Caller does not have the CAP_SYS_ADMIN capability.

     VERSIONS
          Since version 2.23, glibc no longer supports this obsolete
          system call.

     CONFORMING TO
          bdflush() is Linux-specific and should not be used in pro-
          grams intended to be portable.

     SEE ALSO
          sync(1), fsync(2), sync(2)

     COLOPHON
          This page is part of release 5.10 of the Linux man-pages
          project.  A description of the project, information about
          reporting bugs, and the latest version of this page, can be
          found at https://www.kernel.org/doc/man-pages/.

     Page 2                        Linux             (printed 5/24/22)