[libvirt] Storage pool support for large scale deployments

I am using libvirt for large scale deployment of virtual machines. I ran into an issue where virConnectListStoragePools and virConnectListDefinedStoragePools return an error if there are more than 256 pools. The following patch increases this limitation. Currently, I am only using in the neighborhood of 500 pools, but this is likely to grow into the tens of thousands. This patch did not cause any test failures. I wrote some test code to verify the fix worked. The test code and the results follow. TEST CODE: /* pool-test src code */ #include <libvirt.h> #include <stdlib.h> #include <stdio.h> static int get_active_pools(virConnectPtr vir_conn) { int ret_code = -1; int rc = -1; int num_pools = -1; char** pools = NULL; printf("Before virConnectNumOfStoragePools\n"); num_pools = virConnectNumOfStoragePools(vir_conn); printf("After virConnectNumOfStoragePools\n"); if(0 >= num_pools) goto cleanup; pools = malloc(sizeof(*pools) * num_pools); printf("Before virConnectListStoragePools\n"); rc = virConnectListStoragePools(vir_conn, pools, num_pools); printf("After virConnectListStoragePools\n"); if(-1 == rc) goto cleanup; for(int i = 0; i < num_pools; ++i) { if(NULL != pools[i]) free(pools[i]); } ret_code = num_pools; cleanup: if(NULL != pools) free(pools); return ret_code; } static int get_inactive_pools(virConnectPtr vir_conn) { int ret_code = -1; int rc = -1; int num_pools = -1; char** pools = NULL; printf("Before virConnectNumOfDefinedStoragePools\n"); num_pools = virConnectNumOfDefinedStoragePools(vir_conn); printf("After virConnectNumOfDefinedStoragePools\n"); if(0 >= num_pools) goto cleanup; pools = malloc(sizeof(*pools) * num_pools); printf("Before virConnectListDefinedStoragePools\n"); rc = virConnectListDefinedStoragePools(vir_conn, pools, num_pools); printf("After virConnectListDefinedStoragePools\n"); if(-1 == rc) goto cleanup; for(int i = 0; i < num_pools; ++i) { if(NULL != pools[i]) free(pools[i]); } ret_code = num_pools; cleanup: if(NULL != pools) free(pools); return ret_code; } int main(int argc, char** argv) { virConnectPtr conn = virConnectOpen("qemu:///system"); printf("Active: %d\n" , get_active_pools(conn )); printf("Inactive: %d\n", get_inactive_pools(conn)); virConnectClose(conn); return 0; } TEST RESULTS PRE-PATCH: # for i in `ls -1 /etc/libvirt/storage/*`; do virsh pool-start $(basename $i .xml); done &>/dev/null # ~/pool-test Before virConnectNumOfStoragePools After virConnectNumOfStoragePools Before virConnectListStoragePools libvir: Remote error : too many remote undefineds: 407 > 256 After virConnectListStoragePools Active: -1 Before virConnectNumOfDefinedStoragePools After virConnectNumOfDefinedStoragePools Inactive: -1 # for i in `ls -1 /etc/libvirt/storage/*`; do virsh pool-destroy $(basename $i .xml); done &>/dev/null # ~/pool-test Before virConnectNumOfStoragePools After virConnectNumOfStoragePools Active: -1 Before virConnectNumOfDefinedStoragePools After virConnectNumOfDefinedStoragePools Before virConnectListDefinedStoragePools libvir: Remote error : too many remote undefineds: 407 > 256 After virConnectListDefinedStoragePools Inactive: -1 TEST RESULTS POST-PATCH: # for i in `ls -1 /etc/libvirt/storage/*`; do virsh pool-start $(basename $i .xml); done &>/dev/null # ~/pool-test Before virConnectNumOfStoragePools After virConnectNumOfStoragePools Before virConnectListStoragePools After virConnectListStoragePools Active: 407 Before virConnectNumOfDefinedStoragePools After virConnectNumOfDefinedStoragePools Inactive: -1 # for i in `ls -1 /etc/libvirt/storage/*`; do virsh pool-destroy $(basename $i .xml); done &>/dev/null # ~/pool-test Before virConnectNumOfStoragePools After virConnectNumOfStoragePools Active: -1 Before virConnectNumOfDefinedStoragePools After virConnectNumOfDefinedStoragePools Before virConnectListDefinedStoragePools After virConnectListDefinedStoragePools Inactive: 407