Re: [PATCH for-next v10 07/17] RDMA/rxe: Use kzmalloc/kfree for mca

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Feb 01, 2022 at 02:00:09PM -0600, Bob Pearson wrote:


> as currently written the local variable has a kref obtained from the kref_get in
> rxe_lookup_mcg or the kref_init in rxe_init_mcg if it is newly created. This ref is
> dropped when the local variable goes out of scope. To protect the mcg when it is
> inactive at least one more ref is required. I take an additional ref in rxe_get_mcg
> if the mcg is created to protect the pointer in the red-black tree. This persists
> for the lifetime of the object until it is destroyed when it is removed from the tree
> and has the longest scope. This is enough to keep the object alive (it works fine BTW.)
> It is also possible to take ref's representing the pointers in the list but they
> wouldn't add anything.

I think I got it upside down, but OK this works for me. What was
kbuild complaining about?

> On the other point. Is it standard practice to user ERRPTRs in the
> kernel rather than return arguments? I seem to have seen both styles
> used but it may have been my imagination. I don't have any
> preference here but sometimes choose one or the other in parallel
> flows to make comparable routines in the flows have similar
> interfaces.

Always prefer errptrs.

Jason