[PATCH] nvmet-fc: use zero-sized array and struct_size() in kzalloc()

[PATCH] nvmet-fc: use zero-sized array and struct_size() in kzalloc()

[Gustavo A. R. Silva]

Update the code to use a zero-sized array instead of a pointer in
structure nvmet_fc_tgt_queue and use struct_size() in kzalloc().

Notice that 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 foo {
	int stuff;
	struct boo entry[];
};

instance = kzalloc(sizeof(struct foo) + sizeof(struct boo) * count, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can now
use the new struct_size() helper:

instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/nvme/target/fc.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/target/fc.c b/drivers/nvme/target/fc.c
index 1e9654f04c60..23baec38f97e 100644
--- a/drivers/nvme/target/fc.c
+++ b/drivers/nvme/target/fc.c
@@ -128,12 +128,12 @@ struct nvmet_fc_tgt_queue {
 	struct nvmet_cq			nvme_cq;
 	struct nvmet_sq			nvme_sq;
 	struct nvmet_fc_tgt_assoc	*assoc;
-	struct nvmet_fc_fcp_iod		*fod;		/* array of fcp_iods */
 	struct list_head		fod_list;
 	struct list_head		pending_cmd_list;
 	struct list_head		avail_defer_list;
 	struct workqueue_struct		*work_q;
 	struct kref			ref;
+	struct nvmet_fc_fcp_iod		fod[];		/* array of fcp_iods */
 } __aligned(sizeof(unsigned long long));
 
 struct nvmet_fc_tgt_assoc {
@@ -588,9 +588,7 @@ nvmet_fc_alloc_target_queue(struct nvmet_fc_tgt_assoc *assoc,
 	if (qid > NVMET_NR_QUEUES)
 		return NULL;
 
-	queue = kzalloc((sizeof(*queue) +
-				(sizeof(struct nvmet_fc_fcp_iod) * sqsize)),
-				GFP_KERNEL);
+	queue = kzalloc(struct_size(queue, fod, sqsize), GFP_KERNEL);
 	if (!queue)
 		return NULL;
 
@@ -603,7 +601,6 @@ nvmet_fc_alloc_target_queue(struct nvmet_fc_tgt_assoc *assoc,
 	if (!queue->work_q)
 		goto out_a_put;
 
-	queue->fod = (struct nvmet_fc_fcp_iod *)&queue[1];
 	queue->qid = qid;
 	queue->sqsize = sqsize;
 	queue->assoc = assoc;
-- 
2.20.1

Re: [PATCH] nvmet-fc: use zero-sized array and struct_size() in kzalloc()

[Joe Perches]

On Sat, 2019-02-23 at 12:51 -0600, Gustavo A. R. Silva wrote:
> Update the code to use a zero-sized array instead of a pointer in
> structure nvmet_fc_tgt_queue and use struct_size() in kzalloc().
[]
> This code was detected with the help of Coccinelle.

Really?
Impressive script that found this one.

> diff --git a/drivers/nvme/target/fc.c b/drivers/nvme/target/fc.c
[]
> @@ -128,12 +128,12 @@ struct nvmet_fc_tgt_queue {
>  	struct nvmet_cq			nvme_cq;
>  	struct nvmet_sq			nvme_sq;
>  	struct nvmet_fc_tgt_assoc	*assoc;
> -	struct nvmet_fc_fcp_iod		*fod;		/* array of fcp_iods */
>  	struct list_head		fod_list;
>  	struct list_head		pending_cmd_list;
>  	struct list_head		avail_defer_list;
>  	struct workqueue_struct		*work_q;
>  	struct kref			ref;
> +	struct nvmet_fc_fcp_iod		fod[];		/* array of fcp_iods */
>  } __aligned(sizeof(unsigned long long));

Moving a pointer from the middle of a struct to
the end seems unusual for coccinelle.

Re: [PATCH] nvmet-fc: use zero-sized array and struct_size() in kzalloc()

[Gustavo A. R. Silva]

Hey Joe,

On 2/23/19 2:05 PM, Joe Perches wrote:
> On Sat, 2019-02-23 at 12:51 -0600, Gustavo A. R. Silva wrote:
>> Update the code to use a zero-sized array instead of a pointer in
>> structure nvmet_fc_tgt_queue and use struct_size() in kzalloc().
> []
>> This code was detected with the help of Coccinelle.
> 
> Really?
> Impressive script that found this one.
> 

See my comments below.

>> diff --git a/drivers/nvme/target/fc.c b/drivers/nvme/target/fc.c
> []
>> @@ -128,12 +128,12 @@ struct nvmet_fc_tgt_queue {
>>  	struct nvmet_cq			nvme_cq;
>>  	struct nvmet_sq			nvme_sq;
>>  	struct nvmet_fc_tgt_assoc	*assoc;
>> -	struct nvmet_fc_fcp_iod		*fod;		/* array of fcp_iods */
>>  	struct list_head		fod_list;
>>  	struct list_head		pending_cmd_list;
>>  	struct list_head		avail_defer_list;
>>  	struct workqueue_struct		*work_q;
>>  	struct kref			ref;
>> +	struct nvmet_fc_fcp_iod		fod[];		/* array of fcp_iods */
>>  } __aligned(sizeof(unsigned long long));
> 
> Moving a pointer from the middle of a struct to
> the end seems unusual for coccinelle.
> 
> 

Notice that the commit log says "detected", which does not imply
the script made the transformation by itself. :)

And all the script detected was this piece of code:

	queue = kzalloc((sizeof(*queue) +
				(sizeof(struct nvmet_fc_fcp_iod) * sqsize)),
				GFP_KERNEL);


Thanks
--
Gustavo

Re: [PATCH] nvmet-fc: use zero-sized array and struct_size() in kzalloc()

[Gustavo A. R. Silva]

On 2/23/19 2:28 PM, Gustavo A. R. Silva wrote:
> Hey Joe,
> 
> On 2/23/19 2:05 PM, Joe Perches wrote:
>> On Sat, 2019-02-23 at 12:51 -0600, Gustavo A. R. Silva wrote:
>>> Update the code to use a zero-sized array instead of a pointer in
>>> structure nvmet_fc_tgt_queue and use struct_size() in kzalloc().
>> []
>>> This code was detected with the help of Coccinelle.
>>
>> Really?
>> Impressive script that found this one.
>>
> 
> See my comments below.
> 
>>> diff --git a/drivers/nvme/target/fc.c b/drivers/nvme/target/fc.c
>> []
>>> @@ -128,12 +128,12 @@ struct nvmet_fc_tgt_queue {
>>>  	struct nvmet_cq			nvme_cq;
>>>  	struct nvmet_sq			nvme_sq;
>>>  	struct nvmet_fc_tgt_assoc	*assoc;
>>> -	struct nvmet_fc_fcp_iod		*fod;		/* array of fcp_iods */
>>>  	struct list_head		fod_list;
>>>  	struct list_head		pending_cmd_list;
>>>  	struct list_head		avail_defer_list;
>>>  	struct workqueue_struct		*work_q;
>>>  	struct kref			ref;
>>> +	struct nvmet_fc_fcp_iod		fod[];		/* array of fcp_iods */
>>>  } __aligned(sizeof(unsigned long long));
>>
>> Moving a pointer from the middle of a struct to
>> the end seems unusual for coccinelle.
>>
>>
> 
> Notice that the commit log says "detected", which does not imply
> the script made the transformation by itself. :)
> 
> And all the script detected was this piece of code:
> 
> 	queue = kzalloc((sizeof(*queue) +
> 				(sizeof(struct nvmet_fc_fcp_iod) * sqsize)),
> 				GFP_KERNEL);
> 
> 

Which is enough to mention the tool.

Thanks
--
Gustavo

Re: [PATCH] nvmet-fc: use zero-sized array and struct_size() in kzalloc()

[Christoph Hellwig]

James, can you take a look at this one?

On Sat, Feb 23, 2019 at 12:51:08PM -0600, Gustavo A. R. Silva wrote:
> Update the code to use a zero-sized array instead of a pointer in
> structure nvmet_fc_tgt_queue and use struct_size() in kzalloc().
> 
> Notice that 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 foo {
> 	int stuff;
> 	struct boo entry[];
> };
> 
> instance = kzalloc(sizeof(struct foo) + sizeof(struct boo) * count, GFP_KERNEL);
> 
> Instead of leaving these open-coded and prone to type mistakes, we can now
> use the new struct_size() helper:
> 
> instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  drivers/nvme/target/fc.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/nvme/target/fc.c b/drivers/nvme/target/fc.c
> index 1e9654f04c60..23baec38f97e 100644
> --- a/drivers/nvme/target/fc.c
> +++ b/drivers/nvme/target/fc.c
> @@ -128,12 +128,12 @@ struct nvmet_fc_tgt_queue {
>  	struct nvmet_cq			nvme_cq;
>  	struct nvmet_sq			nvme_sq;
>  	struct nvmet_fc_tgt_assoc	*assoc;
> -	struct nvmet_fc_fcp_iod		*fod;		/* array of fcp_iods */
>  	struct list_head		fod_list;
>  	struct list_head		pending_cmd_list;
>  	struct list_head		avail_defer_list;
>  	struct workqueue_struct		*work_q;
>  	struct kref			ref;
> +	struct nvmet_fc_fcp_iod		fod[];		/* array of fcp_iods */
>  } __aligned(sizeof(unsigned long long));
>  
>  struct nvmet_fc_tgt_assoc {
> @@ -588,9 +588,7 @@ nvmet_fc_alloc_target_queue(struct nvmet_fc_tgt_assoc *assoc,
>  	if (qid > NVMET_NR_QUEUES)
>  		return NULL;
>  
> -	queue = kzalloc((sizeof(*queue) +
> -				(sizeof(struct nvmet_fc_fcp_iod) * sqsize)),
> -				GFP_KERNEL);
> +	queue = kzalloc(struct_size(queue, fod, sqsize), GFP_KERNEL);
>  	if (!queue)
>  		return NULL;
>  
> @@ -603,7 +601,6 @@ nvmet_fc_alloc_target_queue(struct nvmet_fc_tgt_assoc *assoc,
>  	if (!queue->work_q)
>  		goto out_a_put;
>  
> -	queue->fod = (struct nvmet_fc_fcp_iod *)&queue[1];
>  	queue->qid = qid;
>  	queue->sqsize = sqsize;
>  	queue->assoc = assoc;
> -- 
> 2.20.1
---end quoted text---

Re: [PATCH] nvmet-fc: use zero-sized array and struct_size() in kzalloc()

[James Smart]

On 2/23/2019 10:51 AM, Gustavo A. R. Silva wrote:
> Update the code to use a zero-sized array instead of a pointer in
> structure nvmet_fc_tgt_queue and use struct_size() in kzalloc().
>
> Notice that 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 foo {
> 	int stuff;
> 	struct boo entry[];
> };
>
> instance = kzalloc(sizeof(struct foo) + sizeof(struct boo) * count, GFP_KERNEL);
>
> Instead of leaving these open-coded and prone to type mistakes, we can now
> use the new struct_size() helper:
>
> instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);
>
> This code was detected with the help of Coccinelle.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>   drivers/nvme/target/fc.c | 7 ++-----
>   1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/nvme/target/fc.c b/drivers/nvme/target/fc.c
> index 1e9654f04c60..23baec38f97e 100644
> --- a/drivers/nvme/target/fc.c
> +++ b/drivers/nvme/target/fc.c
> @@ -128,12 +128,12 @@ struct nvmet_fc_tgt_queue {
>   	struct nvmet_cq			nvme_cq;
>   	struct nvmet_sq			nvme_sq;
>   	struct nvmet_fc_tgt_assoc	*assoc;
> -	struct nvmet_fc_fcp_iod		*fod;		/* array of fcp_iods */
>   	struct list_head		fod_list;
>   	struct list_head		pending_cmd_list;
>   	struct list_head		avail_defer_list;
>   	struct workqueue_struct		*work_q;
>   	struct kref			ref;
> +	struct nvmet_fc_fcp_iod		fod[];		/* array of fcp_iods */
>   } __aligned(sizeof(unsigned long long));
>   
>   struct nvmet_fc_tgt_assoc {
> @@ -588,9 +588,7 @@ nvmet_fc_alloc_target_queue(struct nvmet_fc_tgt_assoc *assoc,
>   	if (qid > NVMET_NR_QUEUES)
>   		return NULL;
>   
> -	queue = kzalloc((sizeof(*queue) +
> -				(sizeof(struct nvmet_fc_fcp_iod) * sqsize)),
> -				GFP_KERNEL);
> +	queue = kzalloc(struct_size(queue, fod, sqsize), GFP_KERNEL);
>   	if (!queue)
>   		return NULL;
>   
> @@ -603,7 +601,6 @@ nvmet_fc_alloc_target_queue(struct nvmet_fc_tgt_assoc *assoc,
>   	if (!queue->work_q)
>   		goto out_a_put;
>   
> -	queue->fod = (struct nvmet_fc_fcp_iod *)&queue[1];
>   	queue->qid = qid;
>   	queue->sqsize = sqsize;
>   	queue->assoc = assoc;

Reviewed-by:  James Smart <james.smart@broadcom.com>

I guess this is a better style.

-- james

Re: [PATCH] nvmet-fc: use zero-sized array and struct_size() in kzalloc()

[Christoph Hellwig]

Thanks,

applied to nvme-5.2.

Re: [PATCH] nvmet-fc: use zero-sized array and struct_size() in kzalloc()

[Gustavo A. R. Silva]

On 3/12/19 2:33 PM, Christoph Hellwig wrote:
> Thanks,
> 
> applied to nvme-5.2.
> 

Great.

Thanks, Christoph.

--
Gustavo