On Fri, May 24, 2019 at 9:07 AM Larry Bassel <larry.bassel@xxxxxxxxxx> wrote: > On 14 May 19 16:01, Kirill A. Shutemov wrote: > > On Thu, May 09, 2019 at 09:05:33AM -0700, Larry Bassel wrote: [..] > > > diff --git a/mm/memory.c b/mm/memory.c > > > index f7d962d..4c1814c 100644 > > > --- a/mm/memory.c > > > +++ b/mm/memory.c > > > @@ -3845,6 +3845,109 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf) > > > return 0; > > > } > > > > > > +#ifdef CONFIG_MAY_SHARE_FSDAX_PMD > > > +static pmd_t *huge_pmd_offset(struct mm_struct *mm, > > > + unsigned long addr, unsigned long sz) > > > > Could you explain what this function suppose to do? > > > > As far as I can see vma_mmu_pagesize() is always PAGE_SIZE of DAX > > filesystem. So we have 'sz' == PAGE_SIZE here. > > I thought so too, but in my testing I found that vma_mmu_pagesize() returns > 4KiB, which differs from the DAX filesystem's 2MiB pagesize. A given filesystem-dax vma is allowed to support both 4K and 2M mappings, so the vma_mmu_pagesize() is not granular enough to describe the capabilities of a filesystem-dax vma. In the device-dax case, where there are mapping guarantees, the implementation does arrange for vma_mmu_pagesize() to reflect the right page size.
