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
