On Wed, Jun 24, 2020 at 11:52:36AM +0800, Baoquan He wrote: >On 06/24/20 at 11:46am, Wei Yang wrote: >> On Wed, Jun 24, 2020 at 09:47:37AM +0800, Baoquan He wrote: >> >On 06/23/20 at 05:21pm, Dan Williams wrote: >> >> On Tue, Jun 23, 2020 at 2:43 AM Wei Yang >> >> <richard.weiyang@xxxxxxxxxxxxxxxxx> wrote: >> >> > >> >> > For early sections, we assumes its memmap will never be partially >> >> > removed. But current behavior breaks this. >> >> >> >> Where do we assume that? >> >> >> >> The primary use case for this was mapping pmem that collides with >> >> System-RAM in the same 128MB section. That collision will certainly be >> >> depopulated on-demand depending on the state of the pmem device. So, >> >> I'm not understanding the problem or the benefit of this change. >> > >> >I was also confused when review this patch, the patch log is a little >> >short and simple. From the current code, with SPARSE_VMEMMAP enabled, we >> >do build memmap for the whole memory section during boot, even though >> >some of them may be partially populated. We just mark the subsection map >> >for present pages. >> > >> >Later, if pmem device is mapped into the partially boot memory section, >> >we just fill the relevant subsection map, do return directly, w/o building >> >the memmap for it, in section_activate(). Because the memmap for the >> >unpresent RAM part have been there. I guess this is what Wei is trying to >> >do to keep the behaviour be consistent for pmem device adding, or >> >pmem device removing and later adding again. >> > >> >Please correct me if I am wrong. >> >> You are right here. >> >> > >> >To me, fixing it looks good. But a clear doc or code comment is >> >necessary so that people can understand the code with less time. >> >Leaving it as is doesn't cause harm. I personally tend to choose >> >the former. >> > >> >> The former is to add a clear doc? > >Sorry for the confusion. The former means the fix in your patch. Maybe a >improved log and some code comment adding can make it more perfect. > Sure, I would try to add more log and comments, in case you have some good suggestion, just let me know :) -- Wei Yang Help you, Help me
