lvm_querylv Subroutine

Purposes

Queries a logical volume and returns all pertinent information.

Library

Logical Volume Manager Library (liblvm.a)

Syntax

#include <lvm.h>

int lvm_querylv (LV_ID, QueryLV, PVName)
struct lv_id *LV_ID;
struct querylv **QueryLV;
char *PVName;

Description

Note: You must have root user authority to use this subroutine.

The lvm_querylv subroutine returns information for the logical volume specified by the LV_ID parameter.

The querylv structure, found in the lvm.h file, is defined as follows:

struct querylv {
      char lvname[LVM_NAMESIZ];  
      struct unique_id vg_id;  
      long maxsize;
      long mirror_policy;
      long lv_state;
      long currentsize;
      long ppsize;
      long permissions;
      long bb_relocation;
      long write_verify;
      long mirwrt_consist;
      long open_close;
      struct pp *mirrors[LVM_NUMCOPIES]  
}
struct pp { 
      struct unique_id pv_id;  
      long lp_num;
      long pp_num;
      long ppstate;
 }

All other fields are described in the lvm_createlv subroutine.

The PVName parameter enables the user to query from a volume group descriptor area on a specific physical volume instead of from the Logical Volume Manager's (LVM) most recent, in-memory copy of the descriptor area. This method should only be used if the volume group is varied off.

Note: The data returned is not guaranteed to be the most recent or correct, and it can reflect a back-level descriptor area.

The PVName parameter should specify either the full path name of the physical volume that contains the descriptor area to query, or a single file name that must reside in the /dev directory (for example, rhdisk1). This parameter must be a null-terminated string between 1 and LVM_NAMESIZ bytes, including the null byte, and must represent a raw device entry. If a raw or character device is not specified for the PVName parameter, the LVM adds an r to the file name to have a raw device name. If there is no raw device entry for this name, the LVM returns the LVM_NOTCHARDEV error code.

If a PVName parameter is specified, only the minor_num field of the LV_ID parameter need be supplied. The LVM fills in the vg_id field and returns it to the user. If the user wishes to query from the LVM's in-memory copy, the PVName parameter should be set to null. When using this method of query, the volume group must be varied on, or an error is returned.

Note: As long as the PVName parameter is not null, the LVM will attempt a query from a physical volume and not from its in-memory copy of data.

In addition to the PVName parameter, the caller passes the ID of the logical volume to be queried (LV_ID parameter) and the address of a pointer to the querylv structure, specified by the QueryLV parameter. The LVM separately allocates the space needed for the querylv structure and the struct pp arrays, and returns the querylv structure's address in the pointer variable passed in by the user. The user is responsible for freeing the space by first freeing the struct pp pointers in the mirrors array and then freeing the querylv structure.

Parameters

Return Values

If the lvm_querylv subroutine is successful, it returns a value of 0.

Error Codes

If the lvm_querylv subroutine does not complete successfully, it returns one of the following values:

If a physical volume name has been passed, requesting that the query originate from a specific physical volume, one of the following error codes is returned:

Implementation Specifics

This subroutine is part of Base Operating System (BOS) Runtime.

Related Information

The lvm_varyonvg subroutine, lvm_createlv subroutine.

List of Logical Volume Subroutines and Logical Volume Programming Overview in AIX Version 4.3 General Programming Concepts: Writing and Debugging Programs.