[PATCH][next] nfsd: Replace one-element array with flexible-array member

[PATCH][next] nfsd: Replace one-element array with flexible-array member

[Gustavo A. R. Silva]

One-element arrays are deprecated, and we are replacing them with
flexible array members instead. So, replace a one-element array
with a flexible-arrayº member in struct vbi_anc_data and refactor
the rest of the code, accordingly.

This results in no differences in binary output.

Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/298
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 fs/nfsd/nfs4callback.c | 2 +-
 fs/nfsd/xdr4.h         | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index 4039ffcf90ba..2c688d51135d 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -353,7 +353,7 @@ encode_cb_recallany4args(struct xdr_stream *xdr,
 {
 	encode_nfs_cb_opnum4(xdr, OP_CB_RECALL_ANY);
 	encode_uint32(xdr, ra->ra_keep);
-	encode_bitmap4(xdr, ra->ra_bmval, ARRAY_SIZE(ra->ra_bmval));
+	encode_bitmap4(xdr, ra->ra_bmval, 1);
 	hdr->nops++;
 }
 
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index 510978e602da..68072170eac8 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -899,7 +899,7 @@ struct nfsd4_operation {
 struct nfsd4_cb_recall_any {
 	struct nfsd4_callback	ra_cb;
 	u32			ra_keep;
-	u32			ra_bmval[1];
+	u32			ra_bmval[];
 };
 
 #endif
-- 
2.34.1

Re: [PATCH][next] nfsd: Replace one-element array with flexible-array member

[Chuck Lever]

On Tue, May 23, 2023 at 06:44:23PM -0600, Gustavo A. R. Silva wrote:
> One-element arrays are deprecated, and we are replacing them with
> flexible array members instead. So, replace a one-element array
> with a flexible-arrayº member in struct vbi_anc_data and refactor

I don't know what "struct vbi_anc_data" is. Is the patch description
correct?


> the rest of the code, accordingly.
> 
> This results in no differences in binary output.
> 
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/298
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

> ---
>  fs/nfsd/nfs4callback.c | 2 +-
>  fs/nfsd/xdr4.h         | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
> index 4039ffcf90ba..2c688d51135d 100644
> --- a/fs/nfsd/nfs4callback.c
> +++ b/fs/nfsd/nfs4callback.c
> @@ -353,7 +353,7 @@ encode_cb_recallany4args(struct xdr_stream *xdr,
>  {
>  	encode_nfs_cb_opnum4(xdr, OP_CB_RECALL_ANY);
>  	encode_uint32(xdr, ra->ra_keep);
> -	encode_bitmap4(xdr, ra->ra_bmval, ARRAY_SIZE(ra->ra_bmval));
> +	encode_bitmap4(xdr, ra->ra_bmval, 1);

I find the new code less self-documenting.


>  	hdr->nops++;
>  }
>  
> diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
> index 510978e602da..68072170eac8 100644
> --- a/fs/nfsd/xdr4.h
> +++ b/fs/nfsd/xdr4.h
> @@ -899,7 +899,7 @@ struct nfsd4_operation {
>  struct nfsd4_cb_recall_any {
>  	struct nfsd4_callback	ra_cb;
>  	u32			ra_keep;
> -	u32			ra_bmval[1];
> +	u32			ra_bmval[];

This is not a placeholder for "1 or more elements". We actually want
just a single u32 element in this array. Doesn't this change the
sizeof(struct nfsd4_cb_recall_any) ?


>  };
>  
>  #endif
> -- 
> 2.34.1
> 

Re: [PATCH][next] nfsd: Replace one-element array with flexible-array member

[Gustavo A. R. Silva]

On 5/23/23 19:01, Chuck Lever wrote:
> On Tue, May 23, 2023 at 06:44:23PM -0600, Gustavo A. R. Silva wrote:
>> One-element arrays are deprecated, and we are replacing them with
>> flexible array members instead. So, replace a one-element array
>> with a flexible-arrayº member in struct vbi_anc_data and refactor
> 
> I don't know what "struct vbi_anc_data" is. Is the patch description
> correct?

Oops, copy/paste error. I'll fix it up. :)

> 
> 
>> the rest of the code, accordingly.
>>
>> This results in no differences in binary output.
>>
>> Link: https://github.com/KSPP/linux/issues/79
>> Link: https://github.com/KSPP/linux/issues/298
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> 
>> ---
>>   fs/nfsd/nfs4callback.c | 2 +-
>>   fs/nfsd/xdr4.h         | 2 +-
>>   2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
>> index 4039ffcf90ba..2c688d51135d 100644
>> --- a/fs/nfsd/nfs4callback.c
>> +++ b/fs/nfsd/nfs4callback.c
>> @@ -353,7 +353,7 @@ encode_cb_recallany4args(struct xdr_stream *xdr,
>>   {
>>   	encode_nfs_cb_opnum4(xdr, OP_CB_RECALL_ANY);
>>   	encode_uint32(xdr, ra->ra_keep);
>> -	encode_bitmap4(xdr, ra->ra_bmval, ARRAY_SIZE(ra->ra_bmval));
>> +	encode_bitmap4(xdr, ra->ra_bmval, 1);
> 
> I find the new code less self-documenting.
> 
> 
>>   	hdr->nops++;
>>   }
>>   
>> diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
>> index 510978e602da..68072170eac8 100644
>> --- a/fs/nfsd/xdr4.h
>> +++ b/fs/nfsd/xdr4.h
>> @@ -899,7 +899,7 @@ struct nfsd4_operation {
>>   struct nfsd4_cb_recall_any {
>>   	struct nfsd4_callback	ra_cb;
>>   	u32			ra_keep;
>> -	u32			ra_bmval[1];
>> +	u32			ra_bmval[];
> 
> This is not a placeholder for "1 or more elements". We actually want
> just a single u32 element in this array. Doesn't this change the
> sizeof(struct nfsd4_cb_recall_any) ?

I see. Yes, it does change the size. Can we replace it with a simple
object of type u32? or do you actually need this to stay an array?

Thanks
--
Gustav

> 
> 
>>   };
>>   
>>   #endif
>> -- 
>> 2.34.1
>>

Re: [PATCH][next] nfsd: Replace one-element array with flexible-array member

[Chuck Lever]

On Tue, May 23, 2023 at 07:11:37PM -0600, Gustavo A. R. Silva wrote:
> 
> On 5/23/23 19:01, Chuck Lever wrote:
> > On Tue, May 23, 2023 at 06:44:23PM -0600, Gustavo A. R. Silva wrote:
> > > One-element arrays are deprecated, and we are replacing them with
> > > flexible array members instead. So, replace a one-element array
> > > with a flexible-arrayº member in struct vbi_anc_data and refactor
> > 
> > I don't know what "struct vbi_anc_data" is. Is the patch description
> > correct?
> 
> Oops, copy/paste error. I'll fix it up. :)
> 
> > 
> > 
> > > the rest of the code, accordingly.
> > > 
> > > This results in no differences in binary output.
> > > 
> > > Link: https://github.com/KSPP/linux/issues/79
> > > Link: https://github.com/KSPP/linux/issues/298
> > > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> > 
> > > ---
> > >   fs/nfsd/nfs4callback.c | 2 +-
> > >   fs/nfsd/xdr4.h         | 2 +-
> > >   2 files changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
> > > index 4039ffcf90ba..2c688d51135d 100644
> > > --- a/fs/nfsd/nfs4callback.c
> > > +++ b/fs/nfsd/nfs4callback.c
> > > @@ -353,7 +353,7 @@ encode_cb_recallany4args(struct xdr_stream *xdr,
> > >   {
> > >   	encode_nfs_cb_opnum4(xdr, OP_CB_RECALL_ANY);
> > >   	encode_uint32(xdr, ra->ra_keep);
> > > -	encode_bitmap4(xdr, ra->ra_bmval, ARRAY_SIZE(ra->ra_bmval));
> > > +	encode_bitmap4(xdr, ra->ra_bmval, 1);
> > 
> > I find the new code less self-documenting.
> > 
> > 
> > >   	hdr->nops++;
> > >   }
> > > diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
> > > index 510978e602da..68072170eac8 100644
> > > --- a/fs/nfsd/xdr4.h
> > > +++ b/fs/nfsd/xdr4.h
> > > @@ -899,7 +899,7 @@ struct nfsd4_operation {
> > >   struct nfsd4_cb_recall_any {
> > >   	struct nfsd4_callback	ra_cb;
> > >   	u32			ra_keep;
> > > -	u32			ra_bmval[1];
> > > +	u32			ra_bmval[];
> > 
> > This is not a placeholder for "1 or more elements". We actually want
> > just a single u32 element in this array. Doesn't this change the
> > sizeof(struct nfsd4_cb_recall_any) ?
> 
> I see. Yes, it does change the size. Can we replace it with a simple
> object of type u32? or do you actually need this to stay an array?

It's not impossible to make it a scalar u32, however...

In this area of code, *_bmval is always a bitmap -- an array of u32s.
Helpers like encode_bitmap4() assume an array. I think it would be
less confusing overall to human readers if it remained an array.

In this case, it is a single element array because CB_RECALL_ANY
doesn't happen to use bits above the first 32-bit word of the
bitmap.

We could make it a 2-element array, I think, without harm. Send a
patch for that, and Dai can test it to make sure there are no
unexpected interoperability consequences.

I hope that would avoid suspicious-looking array definitions.


> > >   };
> > >   #endif
> > > -- 
> > > 2.34.1
> > > 

Re: [PATCH][next] nfsd: Replace one-element array with flexible-array member

[Gustavo A. R. Silva]

On 5/23/23 19:31, Chuck Lever wrote:
> On Tue, May 23, 2023 at 07:11:37PM -0600, Gustavo A. R. Silva wrote:
>>
>> On 5/23/23 19:01, Chuck Lever wrote:
>>> On Tue, May 23, 2023 at 06:44:23PM -0600, Gustavo A. R. Silva wrote:
>>>> One-element arrays are deprecated, and we are replacing them with
>>>> flexible array members instead. So, replace a one-element array
>>>> with a flexible-arrayº member in struct vbi_anc_data and refactor
>>>
>>> I don't know what "struct vbi_anc_data" is. Is the patch description
>>> correct?
>>
>> Oops, copy/paste error. I'll fix it up. :)
>>
>>>
>>>
>>>> the rest of the code, accordingly.
>>>>
>>>> This results in no differences in binary output.
>>>>
>>>> Link: https://github.com/KSPP/linux/issues/79
>>>> Link: https://github.com/KSPP/linux/issues/298
>>>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>>>
>>>> ---
>>>>    fs/nfsd/nfs4callback.c | 2 +-
>>>>    fs/nfsd/xdr4.h         | 2 +-
>>>>    2 files changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
>>>> index 4039ffcf90ba..2c688d51135d 100644
>>>> --- a/fs/nfsd/nfs4callback.c
>>>> +++ b/fs/nfsd/nfs4callback.c
>>>> @@ -353,7 +353,7 @@ encode_cb_recallany4args(struct xdr_stream *xdr,
>>>>    {
>>>>    	encode_nfs_cb_opnum4(xdr, OP_CB_RECALL_ANY);
>>>>    	encode_uint32(xdr, ra->ra_keep);
>>>> -	encode_bitmap4(xdr, ra->ra_bmval, ARRAY_SIZE(ra->ra_bmval));
>>>> +	encode_bitmap4(xdr, ra->ra_bmval, 1);
>>>
>>> I find the new code less self-documenting.
>>>
>>>
>>>>    	hdr->nops++;
>>>>    }
>>>> diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
>>>> index 510978e602da..68072170eac8 100644
>>>> --- a/fs/nfsd/xdr4.h
>>>> +++ b/fs/nfsd/xdr4.h
>>>> @@ -899,7 +899,7 @@ struct nfsd4_operation {
>>>>    struct nfsd4_cb_recall_any {
>>>>    	struct nfsd4_callback	ra_cb;
>>>>    	u32			ra_keep;
>>>> -	u32			ra_bmval[1];
>>>> +	u32			ra_bmval[];
>>>
>>> This is not a placeholder for "1 or more elements". We actually want
>>> just a single u32 element in this array. Doesn't this change the
>>> sizeof(struct nfsd4_cb_recall_any) ?
>>
>> I see. Yes, it does change the size. Can we replace it with a simple
>> object of type u32? or do you actually need this to stay an array?
> 
> It's not impossible to make it a scalar u32, however...
> 
> In this area of code, *_bmval is always a bitmap -- an array of u32s.
> Helpers like encode_bitmap4() assume an array. I think it would be
> less confusing overall to human readers if it remained an array.
> 
> In this case, it is a single element array because CB_RECALL_ANY
> doesn't happen to use bits above the first 32-bit word of the
> bitmap.

I see. If this is never going to be treated as a flexible array, then
it can stay as is.

-fstrict-flex-arrays=3 should not warn about this because the array
will never ever be tried to be accessed beyond element 1. :)

Thanks for the feedback!
--
Gustavo

> 
> We could make it a 2-element array, I think, without harm. Send a
> patch for that, and Dai can test it to make sure there are no
> unexpected interoperability consequences.
> 
> I hope that would avoid suspicious-looking array definitions.
> 
> 
>>>>    };
>>>>    #endif
>>>> -- 
>>>> 2.34.1
>>>>