* [PATCH] RDMA: remove null check after call container_of()
@ 2022-05-17 1:33 Haowen Bai
2022-05-17 12:16 ` Jason Gunthorpe
0 siblings, 1 reply; 6+ messages in thread
From: Haowen Bai @ 2022-05-17 1:33 UTC (permalink / raw)
To: Dennis Dalessandro, Jason Gunthorpe, Leon Romanovsky
Cc: Haowen Bai, linux-rdma, linux-kernel
container_of() will never return NULL, so remove useless code.
Signed-off-by: Haowen Bai <baihaowen@meizu.com>
---
drivers/infiniband/sw/rdmavt/vt.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/drivers/infiniband/sw/rdmavt/vt.c b/drivers/infiniband/sw/rdmavt/vt.c
index 59481ae39505..b2d83b4958fc 100644
--- a/drivers/infiniband/sw/rdmavt/vt.c
+++ b/drivers/infiniband/sw/rdmavt/vt.c
@@ -50,8 +50,6 @@ struct rvt_dev_info *rvt_alloc_device(size_t size, int nports)
struct rvt_dev_info *rdi;
rdi = container_of(_ib_alloc_device(size), struct rvt_dev_info, ibdev);
- if (!rdi)
- return rdi;
rdi->ports = kcalloc(nports, sizeof(*rdi->ports), GFP_KERNEL);
if (!rdi->ports)
--
2.7.4
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] RDMA: remove null check after call container_of()
2022-05-17 1:33 [PATCH] RDMA: remove null check after call container_of() Haowen Bai
@ 2022-05-17 12:16 ` Jason Gunthorpe
2022-05-17 17:54 ` Christophe JAILLET
0 siblings, 1 reply; 6+ messages in thread
From: Jason Gunthorpe @ 2022-05-17 12:16 UTC (permalink / raw)
To: Haowen Bai; +Cc: Dennis Dalessandro, Leon Romanovsky, linux-rdma, linux-kernel
On Tue, May 17, 2022 at 09:33:28AM +0800, Haowen Bai wrote:
> container_of() will never return NULL, so remove useless code.
It is confusing here, but it can be null. If you want to do this then
you have to split out the _ib_alloc_device call and check it
seperately.
Jason
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] RDMA: remove null check after call container_of()
2022-05-17 12:16 ` Jason Gunthorpe
@ 2022-05-17 17:54 ` Christophe JAILLET
2022-05-17 18:03 ` Jason Gunthorpe
0 siblings, 1 reply; 6+ messages in thread
From: Christophe JAILLET @ 2022-05-17 17:54 UTC (permalink / raw)
To: Jason Gunthorpe, Haowen Bai
Cc: Dennis Dalessandro, Leon Romanovsky, linux-rdma, linux-kernel
Le 17/05/2022 à 14:16, Jason Gunthorpe a écrit :
> On Tue, May 17, 2022 at 09:33:28AM +0800, Haowen Bai wrote:
>> container_of() will never return NULL, so remove useless code.
>
> It is confusing here, but it can be null.
Hi,
out of curiosity, can you elaborate how it can be NULL?
CJ
> If you want to do this then
> you have to split out the _ib_alloc_device call and check it
> seperately.
>
> Jason
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] RDMA: remove null check after call container_of()
2022-05-17 17:54 ` Christophe JAILLET
@ 2022-05-17 18:03 ` Jason Gunthorpe
2022-05-17 19:42 ` Christophe JAILLET
2022-05-18 1:55 ` baihaowen
0 siblings, 2 replies; 6+ messages in thread
From: Jason Gunthorpe @ 2022-05-17 18:03 UTC (permalink / raw)
To: Christophe JAILLET
Cc: Haowen Bai, Dennis Dalessandro, Leon Romanovsky, linux-rdma,
linux-kernel
On Tue, May 17, 2022 at 07:54:38PM +0200, Christophe JAILLET wrote:
> Le 17/05/2022 à 14:16, Jason Gunthorpe a écrit :
> > On Tue, May 17, 2022 at 09:33:28AM +0800, Haowen Bai wrote:
> > > container_of() will never return NULL, so remove useless code.
> >
> > It is confusing here, but it can be null.
>
> Hi,
>
> out of curiosity, can you elaborate how it can be NULL?
It is guarented/required that that container_of is a 0 offset. The
normal usage of the ib_alloc_device macro:
#define ib_alloc_device(drv_struct, member) \
container_of(_ib_alloc_device(sizeof(struct drv_struct) + \
BUILD_BUG_ON_ZERO(offsetof( \
struct drv_struct, member))), \
struct drv_struct, member)
Enforces this property with a BUILD_BUG_ON
So, if the input pointer to container_of is reliably NULL or ERR_PTR
then the output pointer will be the same.
The rvt code here open codes the call because it is a mid-layer and
the sizeof() calculation above is not correct for it.
Jason
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] RDMA: remove null check after call container_of()
2022-05-17 18:03 ` Jason Gunthorpe
@ 2022-05-17 19:42 ` Christophe JAILLET
2022-05-18 1:55 ` baihaowen
1 sibling, 0 replies; 6+ messages in thread
From: Christophe JAILLET @ 2022-05-17 19:42 UTC (permalink / raw)
To: Jason Gunthorpe
Cc: Dennis Dalessandro, Leon Romanovsky, linux-rdma, linux-kernel,
Haowen Bai
Le 17/05/2022 à 20:03, Jason Gunthorpe a écrit :
> On Tue, May 17, 2022 at 07:54:38PM +0200, Christophe JAILLET wrote:
>> Le 17/05/2022 à 14:16, Jason Gunthorpe a écrit :
>>> On Tue, May 17, 2022 at 09:33:28AM +0800, Haowen Bai wrote:
>>>> container_of() will never return NULL, so remove useless code.
>>>
>>> It is confusing here, but it can be null.
>>
>> Hi,
>>
>> out of curiosity, can you elaborate how it can be NULL?
>
> It is guarented/required that that container_of is a 0 offset. The
> normal usage of the ib_alloc_device macro:
>
> #define ib_alloc_device(drv_struct, member) \
> container_of(_ib_alloc_device(sizeof(struct drv_struct) + \
> BUILD_BUG_ON_ZERO(offsetof( \
> struct drv_struct, member))), \
> struct drv_struct, member)
>
> Enforces this property with a BUILD_BUG_ON
>
> So, if the input pointer to container_of is reliably NULL or ERR_PTR
> then the output pointer will be the same.
>
> The rvt code here open codes the call because it is a mid-layer and
> the sizeof() calculation above is not correct for it.
>
> Jason
>
Crystal clear.
Thank you for the explanation.
CJ
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] RDMA: remove null check after call container_of()
2022-05-17 18:03 ` Jason Gunthorpe
2022-05-17 19:42 ` Christophe JAILLET
@ 2022-05-18 1:55 ` baihaowen
1 sibling, 0 replies; 6+ messages in thread
From: baihaowen @ 2022-05-18 1:55 UTC (permalink / raw)
To: Jason Gunthorpe, Christophe JAILLET
Cc: Dennis Dalessandro, Leon Romanovsky, linux-rdma, linux-kernel
在 2022/5/18 上午2:03, Jason Gunthorpe 写道:
> On Tue, May 17, 2022 at 07:54:38PM +0200, Christophe JAILLET wrote:
>> Le 17/05/2022 à 14:16, Jason Gunthorpe a écrit :
>>> On Tue, May 17, 2022 at 09:33:28AM +0800, Haowen Bai wrote:
>>>> container_of() will never return NULL, so remove useless code.
>>> It is confusing here, but it can be null.
>> Hi,
>>
>> out of curiosity, can you elaborate how it can be NULL?
> It is guarented/required that that container_of is a 0 offset. The
> normal usage of the ib_alloc_device macro:
>
> #define ib_alloc_device(drv_struct, member) \
> container_of(_ib_alloc_device(sizeof(struct drv_struct) + \
> BUILD_BUG_ON_ZERO(offsetof( \
> struct drv_struct, member))), \
> struct drv_struct, member)
>
> Enforces this property with a BUILD_BUG_ON
>
> So, if the input pointer to container_of is reliably NULL or ERR_PTR
> then the output pointer will be the same.
>
> The rvt code here open codes the call because it is a mid-layer and
> the sizeof() calculation above is not correct for it.
>
> Jason
Thank you for the explanation. : )
--
Haowen Bai
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-05-18 1:55 UTC | newest]
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2022-05-17 1:33 [PATCH] RDMA: remove null check after call container_of() Haowen Bai
2022-05-17 12:16 ` Jason Gunthorpe
2022-05-17 17:54 ` Christophe JAILLET
2022-05-17 18:03 ` Jason Gunthorpe
2022-05-17 19:42 ` Christophe JAILLET
2022-05-18 1:55 ` baihaowen
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