On 12/16/14 09:04, Eric Blake wrote:
> A coming patch will make it optionally possible to list backing
> chain block stats; in this mode of operation, block.counts is no
> longer the number of <disks> in the domain, but the number of
> blocks in the array being reported. We still want block.count
> listed first, but rather than iterate the tree twice (once to
> count, and once to list stats), it's easier to just touch things
> up after the fact.
>
> * src/qemu/qemu_driver.c (qemuDomainGetStatsBlock): Compute count
> after the fact.
>
> Signed-off-by: Eric Blake <eblake@xxxxxxxxxx>
> ---
> src/qemu/qemu_driver.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index ef73502..1127312 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -18542,13 +18542,14 @@ qemuDomainGetStatsBlock(virQEMUDriverPtr driver,
> int *maxparams,
> unsigned int privflags)
> {
> - size_t i;
> + size_t i = 0;
> int ret = -1;
> int rc;
> virHashTablePtr stats = NULL;
> qemuDomainObjPrivatePtr priv = dom->privateData;
> bool abbreviated = false;
> virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
> + int count_index = -1;
>
> if (!HAVE_JOB(privflags) || !virDomainObjIsActive(dom)) {
> abbreviated = true; /* it's ok, just go ahead silently */
> @@ -18565,9 +18566,13 @@ qemuDomainGetStatsBlock(virQEMUDriverPtr driver,
> }
> }
>
> - QEMU_ADD_COUNT_PARAM(record, maxparams, "block", dom->def->ndisks);
> + /* When listing backing chains, it's easier to fix up the count
> + * after the iteration than it is to iterate twice; but we still
> + * want count listed first. */
> + count_index = record->nparams;
The index is remembered prior ..
> + QEMU_ADD_COUNT_PARAM(record, maxparams, "block", 0);
to adding the element into the array. As the macro may jump to cleanup
precisely at this moment, if adding of the element failed you'd ...
>
> - for (i = 0; i < dom->def->ndisks; i++) {
> + for (; i < dom->def->ndisks; i++) {
> qemuBlockStats *entry;
> virDomainDiskDefPtr disk = dom->def->disks[i];
>
> @@ -18627,6 +18632,8 @@ qemuDomainGetStatsBlock(virQEMUDriverPtr driver,
> ret = 0;
>
> cleanup:
> + if (count_index >= 0)
> + record->params[count_index].value.ui = i;
Touch a non-existent field here.
if (ret == 0 && count_index >= 0) ...
> virHashFree(stats);
> virObjectUnref(cfg);
> return ret;
>
ACK with the tweak above.
Peter
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