Messages in this thread | | | Date | Tue, 1 Dec 2015 23:04:11 +0200 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH 3/9] mm: postpone page table allocation until do_set_pte() |
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On Tue, Dec 01, 2015 at 12:53:25PM -0800, Dave Hansen wrote: > On 11/18/2015 03:25 PM, Kirill A. Shutemov wrote: > > --- a/mm/filemap.c > > +++ b/mm/filemap.c > > @@ -2068,11 +2068,6 @@ void filemap_map_pages(struct fault_env *fe, > ... > > if (file->f_ra.mmap_miss > 0) > > file->f_ra.mmap_miss--; > > - do_set_pte(fe, page); > > + > > + fe->address += (iter.index - last_pgoff) << PAGE_SHIFT; > > + if (fe->pte) > > + fe->pte += iter.index - last_pgoff; > > + last_pgoff = iter.index; > > + if (do_set_pte(fe, NULL, page)) { > > + /* failed to setup page table: giving up */ > > + if (!fe->pte) > > + break; > > + goto unlock; > > + } > > unlock_page(page); > > goto next; > > Hey Kirill, > > Is there a case here where do_set_pte() returns an error and _still_ > manages to populate fe->pte?
Yes. If the page is already mapped, we will get VM_FAULT_NOPAGE:
do_set_pte() pte_alloc_one_map() !pmd_none(*fe->pmd) => goto map_pte; fe->pte = pte_offset_map_lock() !pte_none(*fe->pte) => return VM_FAULT_NOPAGE;
-- Kirill A. Shutemov
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