| Message ID | 1596034214-15010-1-git-send-email-zhaoqianligood@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: slab: Avoid the use of one-element array and use struct_size() helper | expand |
On Wed, 29 Jul 2020, Qianli Zhao wrote: > From: Qianli Zhao <zhaoqianli@xiaomi.com> > > 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 <zhaoqianli@xiaomi.com> > --- > 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[]; > }; > > /* This is removed in the -mm tree, see https://www.ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-slab-use-a-single-set-of-kmem_caches-for-all-allocations.patch > 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; > > -- > 2.7.4 > >
Hi, If you are going to copy/paste this, please at least CC the people that is originally working on these changes, in this case _me_. One needs to be very careful when doing these transformations. This code doesn't even exist in linux-next. If you want to land your first kernel patch, I encourage you to start in drivers/staging/, while you get the hang of the kernel development process and you know how to work with linux-next. :) Thanks -- Gustavo On 7/29/20 09:50, Qianli Zhao wrote: > From: Qianli Zhao <zhaoqianli@xiaomi.com> > > 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 <zhaoqianli@xiaomi.com> > --- > 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; > >
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;