bdflush(2) — Linux manual page


BDFLUSH(2)              Linux Programmer's Manual             BDFLUSH(2)

NAME         top

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

SYNOPSIS         top

       #include <sys/kdaemon.h>

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

       Note: There is no glibc wrapper for this system call; see

DESCRIPTION         top

       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 value.

       The set of parameters, their values, and their valid ranges are
       defined in the Linux kernel source file fs/buffer.c.

RETURN VALUE         top

       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         top

       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.

VERSIONS         top

       Since version 2.23, glibc no longer supports this obsolete system

CONFORMING TO         top

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

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 5.13 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

Linux                          2021-03-22                     BDFLUSH(2)

Pages that refer to this page: fsync(2)syscalls(2)capabilities(7)