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charset=us-ascii Content-Disposition: inline In-Reply-To: <6d9e36cb-ee4a-00c8-447b-9b75a0262c3a@redhat.com> User-Agent: NeoMutt/20170113 (1.7.2) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Feb 06, 2020 at 02:28:53PM +0100, David Hildenbrand wrote: >On 06.02.20 13:53, Wei Yang wrote: >> When we use SPARSEMEM instead of SPARSEMEM_VMEMMAP, pfn_to_page() >> doesn't work before sparse_init_one_section() is called. This leads to a >> crash when hotplug memory. >> >> We should use memmap as it did. >> >> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") >> Signed-off-by: Wei Yang >> CC: Dan Williams >> --- >> mm/sparse.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/sparse.c b/mm/sparse.c >> index 5a8599041a2a..2efb24ff8f96 100644 >> --- a/mm/sparse.c >> +++ b/mm/sparse.c >> @@ -882,7 +882,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn, >> * Poison uninitialized struct pages in order to catch invalid flags >> * combinations. >> */ >> - page_init_poison(pfn_to_page(start_pfn), sizeof(struct page) * nr_pages); >> + page_init_poison(memmap, sizeof(struct page) * nr_pages); > >If you add sub-sections that don't fall onto the start of the section, > >pfn_to_page(start_pfn) != memmap > >and your patch would break that under SPARSEMEM_VMEMMAP if I am not wrong. > >Instead of memmap, there would have to be something like > >memmap + (start_pfn - SECTION_ALIGN_DOWN(start_pfn)) > >If I am not wrong :) Hi, David, Thanks for your comment. To be hones, I am not familiar with SPARSEMEM_VMEMMAP. Here is my understanding about section_activate() when SPARSEMEM_VMEMMAP is set. section_activate(nid, start_pfn, nr_pages, altmap) populate_section_mmemap(start_pfn, nr_pages, nid, altmap) __populate_section_mmemap(start_pfn, nr_pages, nid, altmap) return pfn_to_page(start_pfn) So the memmap is the page struct for start_pfn when SPARSEMEM_VMEMMAP is set. Maybe I missed some critical part? > >-- >Thanks, > >David / dhildenb -- Wei Yang Help you, Help me