BDFLUSH(2) Linux Programmer's Manual BDFLUSH(2)
bdflush - start, flush, or tune buffer-dirty-flush daemon
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
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 ker-
nel 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
EBUSY An attempt was made to enter the daemon code after another process has already
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(8), update(8)
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Linux 2012-03-05 BDFLUSH(2)