Re: [PATCH v2] mm: cma: support sysfs

From: John Hubbard
Date: Tue Feb 09 2021 - 00:27:56 EST


On 2/8/21 9:18 PM, John Hubbard wrote:
On 2/8/21 8:19 PM, Minchan Kim wrote:
On Mon, Feb 08, 2021 at 05:57:17PM -0800, John Hubbard wrote:
On 2/8/21 3:36 PM, Minchan Kim wrote:
...
        char name[CMA_MAX_NAME];
+#ifdef CONFIG_CMA_SYSFS
+    struct cma_stat    *stat;

This should not be a pointer. By making it a pointer, you've added a bunch of pointless
extra code to the implementation.

Originally, I went with the object lifetime with struct cma as you
suggested to make code simple. However, Greg KH wanted to have
release for kobj_type since it is consistent with other kboject
handling.

Are you talking about the kobj in your new struct cma_stat? That seems
like circular logic if so. I'm guessing Greg just wanted kobj methods
to be used *if* you are dealing with kobjects. That's a narrower point.

I can't imagine that he would have insisted on having additional
allocations just so that kobj freeing methods could be used. :)

I have no objection if Greg agree static kobject is okay in this
case. Greg?


What I meant is, no kobject at all in the struct cma_stat member
variable. The lifetime of the cma_stat member is the same as the
containing struct, so no point in putting a kobject into it.


...unless...are you actually *wanting* to keep the lifetimes separate?
Hmmm, given the short nature of sysfs reads, though, I'd be inclined
to just let the parent object own the lifetime. But maybe I'm missing
some design point here?

thanks,
--
John Hubbard
NVIDIA