Commit 7af5eea9 authored by Alberto Garcia's avatar Alberto Garcia Committed by Kevin Wolf
Browse files

qcow2: Fix Coverity warning when calculating the refcount cache size 



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: default avatarPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: default avatarAlberto Garcia <berto@igalia.com>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent e609fa71

block/qcow2.c

+2 −3
Original line number Diff line number Diff line
@@ -768,6 +768,7 @@ 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);
@@ -804,8 +805,6 @@ 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 */
@@ -825,7 +824,7 @@ 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;

        }

    }