Проект OpenNet: MAN VOP_ATTRIB (9) Ядро (FreeBSD и Linux)

Интерактивная система просмотра системных руководств (man-ов)

VOP_ATTRIB (9)

>> VOP_ATTRIB (9) ( FreeBSD man: Ядро )

BSD mandoc

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:

Fa vp: The vnode of the file.
Fa vap: The attributes of the file.
Fa cred: The user credentials of the calling process.
Fa 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 Fa *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 Fa *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

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