VOP_RDWR(9)

NAME
VOP_READ, VOP_WRITE - read or write a file

SYNOPSIS
#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);

DESCRIPTION
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.

LOCKS
The file should be locked on entry and will still be locked on exit. Rangelock covering the whole i/o range should be owned around the call.

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

ERRORS

[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.

SEE ALSO
uiomove(9), vnode(9)

AUTHORS
This manual page was written by Doug Rabson.