VOP_ATTRIB(9) · carta

NAME

VOP_GETATTR, VOP_SETATTR – get and set attributes on a file or directory

SYNOPSIS

#include <sys/param.h>

#include <sys/vnode.h>

int

VOP_GETATTR(struct vnode *vp, struct vattr *vap, struct ucred *cred, struct thread *td);

int

VOP_SETATTR(struct vnode *vp, struct vattr *vap, struct ucred *cred, struct thread *td);

DESCRIPTION

These entry points manipulate various attributes of a file or directory, including file permissions, owner, group, size, access time and modification time.

The arguments are:

vp: The vnode of the file.
vap: The attributes of the file.
cred: The user credentials of the calling process.
td: The thread.

Attributes which are not being modified by VOP_SETATTR() should be set to the value VNOVAL; VATTR_NULL() may be used to clear all the values, and should generally be used to reset the contents of *vap prior to setting specific values.

LOCKS

VOP_GETATTR() expects the vnode to be locked on entry and will leave the vnode locked on return. The lock type can be either shared or exclusive.

VOP_SETATTR() expects the vnode to be locked on entry and will leave the vnode locked on return. The lock type must be exclusive.

RETURN VALUES

VOP_GETATTR() returns 0 if it was able to retrieve the attribute data via *vap, otherwise an appropriate error is returned. VOP_SETATTR() returns zero if the attributes were changed successfully, otherwise an appropriate error is returned.

PSEUDOCODE

int
vop_getattr(struct vnode *vp, struct vattr *vap,
	    struct ucred *cred, struct thread *td)
{
    /*
     * Fill in the contents of *vap with information from
     * the file system.
     */
    ...;
    return 0;
}
int
vop_setattr(struct vnode *vp, struct vattr *vap,
	    struct ucred *cred, struct thread *td)
{
    /*
     * Check for unsettable attributes.
     */
    if ((vap->va_type != VNON) || (vap->va_nlink != VNOVAL) ||
	(vap->va_fsid != VNOVAL) || (vap->va_fileid != VNOVAL) ||
	(vap->va_blocksize != VNOVAL) || (vap->va_rdev != VNOVAL) ||
	((int)vap->va_bytes != VNOVAL) || (vap->va_gen != VNOVAL)) {
	return (EINVAL);
    }
    if (vap->va_flags != VNOVAL) {
	/*
	 * Set the immutable and append flags of the file.
	 */
    }
    if (vap->va_uid != (uid_t)VNOVAL || vap->va_gid != (gid_t)VNOVAL) {
	/*
	 * Change owner and/or group of the file.
	 */
    }
    if (vap->va_size != VNOVAL) {
	/*
	 * Truncate the file to the specified size.
	 */
    }
    if (vap->va_atime.tv_sec != VNOVAL || vap->va_mtime.tv_sec != VNOVAL) {
	/*
	 * Change access and/or modification time of file.
	 */
    }
    if (vap->va_mode != (mode_t)VNOVAL) {
	/*
	 * Change permissions of file.
	 */
    }
    return 0;
}

ERRORS

[EPERM]: The file is immutable.
[EACCES]: The caller does not have permission to modify the file or directory attributes.
[EROFS]: The file system is read-only.

AUTHORS

This manual page was written by Doug Rabson.