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Wed, 29 Jul 2020 07:50:20 -0700 (PDT) Received: from builder-PowerEdge-R730xd.mioffice.cn ([43.224.245.179]) by smtp.gmail.com with ESMTPSA id o190sm1251827pfd.194.2020.07.29.07.50.17 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 29 Jul 2020 07:50:20 -0700 (PDT) From: Qianli Zhao To: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, zhaoqianli@xiaomi.com Subject: [PATCH] mm: slab: Avoid the use of one-element array and use struct_size() helper Date: Wed, 29 Jul 2020 22:50:14 +0800 Message-Id: <1596034214-15010-1-git-send-email-zhaoqianligood@gmail.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 X-Rspamd-Queue-Id: 3CDFB18479694 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Qianli Zhao There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2]. Make use of the struct_size() helper instead of an open-coded version in order to avoid any potential type mistakes. [1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://github.com/KSPP/linux/issues/21 Signed-off-by: Qianli Zhao --- mm/slab.h | 2 +- mm/slab_common.c | 7 ++----- 2 files changed, 3 insertions(+), 6 deletions(-) diff --git a/mm/slab.h b/mm/slab.h index 74f7e09..c12fb65 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -34,7 +34,7 @@ struct kmem_cache { struct memcg_cache_array { struct rcu_head rcu; - struct kmem_cache *entries[0]; + struct kmem_cache *entries[]; }; /* diff --git a/mm/slab_common.c b/mm/slab_common.c index fe8b684..56f4818 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -166,9 +166,7 @@ static int init_memcg_params(struct kmem_cache *s, if (!memcg_nr_cache_ids) return 0; - arr = kvzalloc(sizeof(struct memcg_cache_array) + - memcg_nr_cache_ids * sizeof(void *), - GFP_KERNEL); + arr = kvzalloc(struct_size(arr, entries, memcg_nr_cache_ids), GFP_KERNEL); if (!arr) return -ENOMEM; @@ -199,8 +197,7 @@ static int update_memcg_params(struct kmem_cache *s, int new_array_size) { struct memcg_cache_array *old, *new; - new = kvzalloc(sizeof(struct memcg_cache_array) + - new_array_size * sizeof(void *), GFP_KERNEL); + new = kvzalloc(struct_size(new, entries, new_array_size), GFP_KERNEL); if (!new) return -ENOMEM;