On Mon, Feb 10, 2020 at 03:54:06PM +0800, Baoquan He wrote: >On 02/10/20 at 02:08pm, Wei Yang wrote: >> On Mon, Feb 10, 2020 at 11:41:05AM +0800, Baoquan He wrote: >> >On 02/10/20 at 07:52am, Wei Yang wrote: >> >> >--- >> >> > mm/sparse.c | 4 +++- >> >> > 1 file changed, 3 insertions(+), 1 deletion(-) >> >> > >> >> >diff --git a/mm/sparse.c b/mm/sparse.c >> >> >index 623755e88255..345d065ef6ce 100644 >> >> >--- a/mm/sparse.c >> >> >+++ b/mm/sparse.c >> >> >@@ -854,13 +854,15 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages, >> >> > ms->usage = NULL; >> >> > } >> >> > memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr); >> >> >- ms->section_mem_map = (unsigned long)NULL; >> >> > } >> >> > >> >> > if (section_is_early && memmap) >> >> > free_map_bootmem(memmap); >> >> > else >> >> > depopulate_section_memmap(pfn, nr_pages, altmap); >> >> >> >> The crash happens in depopulate_section_memmap() when trying to get memmap by >> >> pfn_to_page(). Can we pass memmap directly? >> > >> >Yes, that's also a good idea. While it needs to add a parameter for >> >depopulate_section_memmap(), the parameter is useless for VMEMMAP >> >though, I personally prefer the current fix which is a little simpler. >> > >> >> Not a new parameter, but replace pfn with memmap. >> >> Not sure why the parameter is useless for VMEMMAP? memmap will be assigned to >> start and finally pass to vmemmap_free(). > >In section_deactivate(), per the code comments from Dan, we can know >that: > > /* > * section which only contains bootmem will be handled by > * free_map_bootmem(), including a complete section, or partial > * section which only has memory starting from the begining. > */ > if (section_is_early && memmap) > free_map_bootmem(memmap); > else > /* > * section which contains region mixing bootmem with hot added > * sub-section region, only sub-section region, complete > * section. And in the mxied case, if hot remove the hot added > * sub-section aligned part, no memmap is got in the current > * code. So we still need pfn to calculate it for vmemmap case. > * To me, whenever we need, it looks better that we always use > * pfn to get its own memmap. > */ > depopulate_section_memmap(pfn, nr_pages, altmap); > >This is why I would like to keep the current logic as is,only one line >of code adjusting can fix the issue. Please let me know if I miss >anything. > You are right. I missed this point. > >> >> >Anyway, both is fine to me, I can update if you think passing memmap is >> >better. >> > >> >> >> >> >+ >> >> >+ if(!rc) >> >> >+ ms->section_mem_map = (unsigned long)NULL; >> >> > } >> >> > >> >> > static struct page * __meminit section_activate(int nid, unsigned long pfn, >> >> >-- >> >> >2.17.2 >> >> >> >> -- >> >> Wei Yang >> >> Help you, Help me >> >> >> >> -- >> Wei Yang >> Help you, Help me >> -- Wei Yang Help you, Help me
