Manual Pages  — VOP_RDWR

VOP_READ, VOP_WRITE – read or write a file

SYNOPSIS DESCRIPTION LOCKS RETURN VALUES ERRORS SEE ALSO AUTHORS

#include <sys/param.h>

#include <sys/vnode.h>

#include <sys/uio.h>

int
VOP_READ(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred);

int
VOP_WRITE(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred);

These entry points read or write the contents of a file.

The arguments are:

vp
	The vnode of the file.
uio
	The location of the data to be read or written.
ioflag
	Various flags.
cnp
	The credentials of the caller.

The ioflag argument is used to give directives and hints to the file system. When attempting a read, the high 16 bits are used to provide a read-ahead hint (in units of file system blocks) that the file system should attempt. The low 16 bits are a bit mask which can contain the following flags:

IO_UNIT	Do I/O as atomic unit.
IO_APPEND	Append write to end.
IO_SYNC	Do I/O synchronously.
IO_NODELOCKED
	Underlying node already locked.
IO_NDELAY	FNDELAY flag set in file table.
IO_VMIO	Data already in VMIO space.

The file should be locked on entry and will still be locked on exit.

Zero is returned on success, otherwise an error code is returned.

[EFBIG]
	An attempt was made to write a file that exceeds the process's file size limit or the maximum file size.
[ENOSPC]
	The file system is full.
[EPERM]
	An append-only flag is set on the file, but the caller is attempting to write before the current end of file.

This manual page was written by Doug Rabson.