lkml.org 
[lkml]   [2019]   [Sep]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] ubifs: super: Use struct_size() helper
On Thu, Aug 29, 2019 at 2:50 AM Gustavo A. R. Silva
<gustavo@embeddedor.com> wrote:
>
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
>
> struct ubifs_znode {
> ...
> struct ubifs_zbranch zbranch[];
> };
>
> Make use of the struct_size() helper instead of an open-coded version
> in order to avoid any potential type mistakes.
>
> So, replace the following form:
>
> sizeof(struct ubifs_znode) + c->fanout * sizeof(struct ubifs_zbranch)
>
> with:
>
> struct_size(c->cnext, zbranch, c->fanout)
>
> This code was detected with the help of Coccinelle.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
> fs/ubifs/super.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
> index 2706f13e3eb9..ca86489048c8 100644
> --- a/fs/ubifs/super.c
> +++ b/fs/ubifs/super.c
> @@ -661,8 +661,7 @@ static int init_constants_sb(struct ubifs_info *c)
> long long tmp64;
>
> c->main_bytes = (long long)c->main_lebs * c->leb_size;
> - c->max_znode_sz = sizeof(struct ubifs_znode) +
> - c->fanout * sizeof(struct ubifs_zbranch);
> + c->max_znode_sz = struct_size(c->cnext, zbranch, c->fanout);

First of all, c->fanout is bound checked.
I had to lookup how struct_size() works to understand this
single line of code and why you use the completely unrelated c->cnext here.
Sorry this change does not make the code any better just harder to read.

--
Thanks,
//richard

\
 
 \ /
  Last update: 2019-09-15 23:59    [W:0.026 / U:4.224 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site