From c0d6740c1219f23f0b9a996f02c1ae9cf824b0b3 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Thu, 6 Dec 2018 17:12:28 +0000 Subject: [PATCH 03/15] qcow2: Fix Coverity warning when calculating the refcount cache size RH-Author: Kevin Wolf Message-id: <20181206171240.5674-4-kwolf@redhat.com> Patchwork-id: 83295 O-Subject: [RHEL-8.0 qemu-kvm PATCH 03/15] qcow2: Fix Coverity warning when calculating the refcount cache size Bugzilla: 1656507 RH-Acked-by: Max Reitz RH-Acked-by: John Snow RH-Acked-by: Stefan Hajnoczi From: Alberto Garcia MIN_REFCOUNT_CACHE_SIZE is 4 and the cluster size is guaranteed to be at most 2MB, so the minimum refcount cache size (in bytes) is always going to fit in a 32-bit integer. Coverity doesn't know that, and since we're storing the result in a uint64_t (*refcount_cache_size) it thinks that we need the 64 bits and that we probably want to do a 64-bit multiplication to prevent the result from being truncated. This is a false positive in this case, but it's a fair warning. We could do a 64-bit multiplication to get rid of it, but since we know that a 32-bit variable is enough to store this value let's simply reuse min_refcount_cache, make it a normal int and stop doing casts. Reported-by: Peter Maydell Signed-off-by: Alberto Garcia Reviewed-by: Eric Blake Signed-off-by: Kevin Wolf (cherry picked from commit 7af5eea9b34ffb7a9a9fc25ba71998a02b76e159) Signed-off-by: Kevin Wolf Signed-off-by: Danilo C. L. de Paula --- block/qcow2.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index 4b65e4c..a0f7234 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -775,6 +775,7 @@ static void read_cache_sizes(BlockDriverState *bs, QemuOpts *opts, BDRVQcow2State *s = bs->opaque; uint64_t combined_cache_size; bool l2_cache_size_set, refcount_cache_size_set, combined_cache_size_set; + int min_refcount_cache = MIN_REFCOUNT_CACHE_SIZE * s->cluster_size; combined_cache_size_set = qemu_opt_get(opts, QCOW2_OPT_CACHE_SIZE); l2_cache_size_set = qemu_opt_get(opts, QCOW2_OPT_L2_CACHE_SIZE); @@ -811,8 +812,6 @@ static void read_cache_sizes(BlockDriverState *bs, QemuOpts *opts, } else { 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; /* Assign as much memory as possible to the L2 cache, and * use the remainder for the refcount cache */ @@ -832,7 +831,7 @@ static void read_cache_sizes(BlockDriverState *bs, QemuOpts *opts, * s->cluster_size); } if (!refcount_cache_size_set) { - *refcount_cache_size = MIN_REFCOUNT_CACHE_SIZE * s->cluster_size; + *refcount_cache_size = min_refcount_cache; } } -- 1.8.3.1