btrfs: use struct_size to calculate size of raid hash table

The struct_size macro does the same calculation and is safe regarding
overflows. Though we're not expecting them to happen, use the helper for
clarity.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 406b1ef..c870ef7 100644 (file)
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -206,7 +206,6 @@ int btrfs_alloc_stripe_hash_table(struct btrfs_fs_info *info)
        struct btrfs_stripe_hash *h;
        int num_entries = 1 << BTRFS_STRIPE_HASH_TABLE_BITS;
        int i;
-       int table_size;
 
        if (info->stripe_hash_table)
                return 0;
@@ -218,8 +217,7 @@ int btrfs_alloc_stripe_hash_table(struct btrfs_fs_info *info)
         * Try harder to allocate and fallback to vmalloc to lower the chance
         * of a failing mount.
         */
-       table_size = sizeof(*table) + sizeof(*h) * num_entries;
-       table = kvzalloc(table_size, GFP_KERNEL);
+       table = kvzalloc(struct_size(table, table, num_entries), GFP_KERNEL);
        if (!table)
                return -ENOMEM;