On 15 May 2018 at 16:40, Kevin Wolf <[email protected]> wrote:
> From: Alberto Garcia <[email protected]>
>
> The L2 and refcount caches have default sizes that can be overridden
> using the l2-cache-size and refcount-cache-size (an additional
> parameter named cache-size sets the combined size of both caches).
Hi; Coverity raises a nit about this patch (CID 1391229):
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 2f36e632f9..6d532470a8 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -802,23 +802,30 @@ static void read_cache_sizes(BlockDriverState *bs,
> QemuOpts *opts,
> } else if (refcount_cache_size_set) {
> *l2_cache_size = combined_cache_size - *refcount_cache_size;
> } else {
> - *refcount_cache_size = combined_cache_size
> - / (DEFAULT_L2_REFCOUNT_SIZE_RATIO + 1);
> - *l2_cache_size = combined_cache_size - *refcount_cache_size;
> + uint64_t virtual_disk_size = bs->total_sectors *
> BDRV_SECTOR_SIZE;
> + uint64_t max_l2_cache = virtual_disk_size / (s->cluster_size /
> 8);
> + uint64_t min_refcount_cache =
> + (uint64_t) MIN_REFCOUNT_CACHE_SIZE * s->cluster_size;
Here we have a (uint64_t) cast that ensures we're doing a 64x64 multiply
rather than a 32x32 one...
> +
> + /* Assign as much memory as possible to the L2 cache, and
> + * use the remainder for the refcount cache */
> + if (combined_cache_size >= max_l2_cache + min_refcount_cache) {
> + *l2_cache_size = max_l2_cache;
> + *refcount_cache_size = combined_cache_size - *l2_cache_size;
> + } else {
> + *refcount_cache_size =
> + MIN(combined_cache_size, min_refcount_cache);
> + *l2_cache_size = combined_cache_size - *refcount_cache_size;
> + }
> }
> } else {
> - if (!l2_cache_size_set && !refcount_cache_size_set) {
> + if (!l2_cache_size_set) {
> *l2_cache_size = MAX(DEFAULT_L2_CACHE_BYTE_SIZE,
> (uint64_t)DEFAULT_L2_CACHE_CLUSTERS
> * s->cluster_size);
> - *refcount_cache_size = *l2_cache_size
> - / DEFAULT_L2_REFCOUNT_SIZE_RATIO;
> - } else if (!l2_cache_size_set) {
> - *l2_cache_size = *refcount_cache_size
> - * DEFAULT_L2_REFCOUNT_SIZE_RATIO;
> - } else if (!refcount_cache_size_set) {
> - *refcount_cache_size = *l2_cache_size
> - / DEFAULT_L2_REFCOUNT_SIZE_RATIO;
> + }
> + if (!refcount_cache_size_set) {
> + *refcount_cache_size = MIN_REFCOUNT_CACHE_SIZE * s->cluster_size;
...but in the else clause down here, we don't have the cast, and
Coverity complains that we evaluate a 32-bit result and then
put it in a 64-bit variable. Should this have the (uint64_t)
cast as well ?
> }
> }
>
thanks
-- PMM
