linux-kernel - Re: [PATCH] xfs: use struct

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Date:   Thu, 11 Apr 2019 20:57:14 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xfs: use struct_size() helper



On 4/11/19 7:19 PM, Darrick J. Wong wrote:
> [fixing linux-xfs cc]
> 

Thanks for this.

> On Thu, Apr 11, 2019 at 06:37:58PM -0500, Gustavo A. R. Silva wrote:
>> Make use of the struct_size() helper instead of an open-coded  version
>> in order to avoid any potential type mistakes, in particular in the
>> context in which this code is being used.
>>
>> So, replace code of the following form:
>>
>> sizeof(*alist) + context->count * sizeof(alist->al_offset[0]
>>
>> with:
>>
>> struct_size(alist, al_offset, context->count)
>>
>> and remove unnecessary variable arraytop.
>>
>> This code was detected with the help of Coccinelle.
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> 
> Has this been run through xfstests?
> 

No.  Is this a requirement?

Thanks
--
Gustavo

> --D
> 
>>  fs/xfs/xfs_attr_list.c | 5 +----
>>  1 file changed, 1 insertion(+), 4 deletions(-)
>>
>> diff --git a/fs/xfs/xfs_attr_list.c b/fs/xfs/xfs_attr_list.c
>> index 3d213a7394c5..05e03348553e 100644
>> --- a/fs/xfs/xfs_attr_list.c
>> +++ b/fs/xfs/xfs_attr_list.c
>> @@ -553,7 +553,6 @@ xfs_attr_put_listent(
>>  {
>>  	struct attrlist *alist = (struct attrlist *)context->alist;
>>  	attrlist_ent_t *aep;
>> -	int arraytop;
>>  
>>  	ASSERT(!context->seen_enough);
>>  	ASSERT(!(context->flags & ATTR_KERNOVAL));
>> @@ -572,10 +571,8 @@ xfs_attr_put_listent(
>>  	    ((flags & XFS_ATTR_ROOT) == 0))
>>  		return;
>>  
>> -	arraytop = sizeof(*alist) +
>> -			context->count * sizeof(alist->al_offset[0]);
>>  	context->firstu -= ATTR_ENTSIZE(namelen);
>> -	if (context->firstu < arraytop) {
>> +	if (context->firstu < struct_size(alist, al_offset, context->count)) {
>>  		trace_xfs_attr_list_full(context);
>>  		alist->al_more = 1;
>>  		context->seen_enough = 1;
>> -- 
>> 2.21.0
>>