v_get (BPX1VGT, BPX4VGT) — Convert an FID to a vnode Token

Function

The v_get service returns a vnode token for the file or directory that is represented by the input FID within the mounted file system that is represented by the input VFS token.

Requirements

Operation	Environment
Authorization:	Supervisor state or problem state, any PSW key
Dispatchable unit mode:	Task
Cross memory mode:	PASN = HASN
AMODE (BPX1VGT):	31-bit
AMODE (BPX4VGT):	64-bit
ASC mode:	Primary mode
Interrupt status:	Enabled for interrupts
Locks:	Unlocked
Control parameters:	All parameters must be addressable by the caller and in the primary address space.

Format

CALL BPX1VGT,(VFS_token,
              OSS,
              FID,
              Vnode_token,
              Return_value,
              Return_code,
              Reason_code)

AMODE 64 callers use BPX4VGT with the same parameters.

Parameters

VFS_token

Supplied parameter

Type:: Token
Length:: 8 bytes

The name of an 8-byte area that contains the VFS token for the mounted file system that contains the file or directory that is specified by the FID parameter. This token is obtained from the v_rpn callable service.

OSS

Supplied and returned parameter

Type:: Structure
Length:: OSS#LENGTH (from the BPXYOSS macro)

The name of an area that contains operating-system-specific parameters. This area is mapped by the BPXYOSS macro (see BPXYOSS — Map operating system specific information).

FID

Supplied parameter

Type:: Token
Length:: 8 bytes

The name of an 8-byte area that contains the file identifier of the file or directory for which a vnode token is to be returned. The FID for a file is contained in the attribute structure for the file in the AttrFid field; the ATTR structure describes the attribute structure.

Vnode_token

Returned parameter

Type:: Token
Length:: 8 bytes

The name of an 8-byte area in which the v_get service returns a vnode token of the file or directory that is supplied in the FID parameter. The token is used to identify the file or directory to other callable services.

Return_value

Returned parameter

Type:: Integer
Length:: Fullword

The name of a fullword in which the v_get service returns 0 if the request completes successfully (the file or directory exists), or -1 if the request is not successful.

Return_code

Returned parameter

Type:: Integer
Length:: Fullword

The name of a fullword in which the v_get service stores the return code. The v_get service returns Return_code only if Return_value is -1. See z/OS UNIX System Services Messages and Codes for a complete list of possible return code values. The v_get service can return one of the following values in the Return_code parameter:

Return_code	Explanation
EINVAL	Parameter error; for example, the VFS token parameter is obsolete.The following reason codes can accompany the return code: JRStaleVFSTok, JRInvalidOSS.
EMFILE	The maximum number of vnode tokens have been created.
ENFILE	An error occurred obtaining storage for a vnode token.
EPERM	The operation is not permitted. The caller of the service is not registered as a server.

Reason_code

Returned parameter

Type:: Integer
Length:: Fullword

The name of a fullword in which the v_get service stores the reason code. The v_get service returns Reason_code only if Return_value is -1. Reason_code further qualifies the Return_code value. See z/OS UNIX System Services Messages and Codes for the reason codes.

Usage notes

The FID (file identifier) uniquely identifies a file in a particular mounted file system. For files associated with a physical DASD resource, the FID validly persists across mounting and unmounting of the file system, as well as z/OS UNIX re-IPLS. This distinguishes the FID from the vnode token, which relates to a file in active use, and whose validity persists only until the token is released via the v_rel callable service. Note that automount-managed directories are virtual, and the FID is unique only as long as the directory is being referenced.
A server application uses v_get to convert a FID to a vnode token when it is preparing to use a file, because the Vnode token identifies the file to the other VFS callable services.
The FID for a file is returned in the ATTR structure (see BPXYATTR — Map file attributes for v_ system calls), by such services as v_rpn and v_lookup.
vnode tokens that are returned by the v_get service are not inherited across a fork callable service.
The caller is responsible for freeing vnode tokens that are returned by the v_get service by calling to the v_rel service when they are no longer needed.

Related services

Characteristics and restrictions

A process must be registered as a server before the v_get service is permitted; see v_reg (BPX1VRG, BPX4VRG) — Register a process as a server.

Examples

For an example using this callable service, see BPX1VGT, BPX4VGT (v_get).