VOP_ATTRIB(9) MidnightBSD Kernel Developer’s Manual VOP_ATTRIB(9)

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.

SEE ALSO

VFS(9), vnode(9), VOP_ACCESS(9)

AUTHORS

This manual page was written by Doug Rabson.

MidnightBSD 0.3 July 24, 1996 MidnightBSD 0.3