Messages in this thread | | | Subject | Re: [mm 4.15-rc8] Random oopses under memory pressure. | From | Dave Hansen <> | Date | Thu, 18 Jan 2018 06:51:37 -0800 |
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On 01/18/2018 06:45 AM, Kirill A. Shutemov wrote: > On Thu, Jan 18, 2018 at 06:38:10AM -0800, Dave Hansen wrote: >> On 01/18/2018 05:12 AM, Kirill A. Shutemov wrote: >>> - if (pte_page(*pvmw->pte) - pvmw->page >= >>> - hpage_nr_pages(pvmw->page)) { >> Is ->pte guaranteed to map a page which is within the same section as >> pvmw->page? Otherwise, with sparsemem (non-vmemmap), the pointer >> arithmetic won't work. > No, it's not guaranteed. It can be arbitrary page. > > The arithmetic won't work because they are different "memory objects"?
No, because sections' mem_map[]s can be allocated non-contiguously. Section 1's might be a lower virtual address than Section 0's.
They're allocated not unlike this:
mem_section[0]->section_mem_map = kmalloc(SECTION_SIZE); mem_section[1]->section_mem_map = kmalloc(SECTION_SIZE); ...
The first pfn in section 1 and the last pfn in section 0 are adjacent PFNs, but their 'struct page' might have virtual addresses that are TB apart.
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