On Thu 28-09-17 18:21:18, Dan Williams wrote:
> VM_MIXEDMAP is used by dax to direct mm paths like vm_normal_page() that
> the memory page it is dealing with is not typical memory from the linear
> map. The get_user_pages_fast() path, since it does not resolve the vma,
> is already using {pte,pmd}_devmap() as a stand-in for VM_MIXEDMAP, so we
> use that as a VM_MIXEDMAP replacement in some locations. In the cases
> where there is no pte to consult we fallback to using vma_is_dax() to
> detect the VM_MIXEDMAP special case.
Well, I somewhat dislike the vma_is_dax() checks sprinkled around. That
seems rather errorprone (easy to forget about it when adding new check
somewhere). Can we possibly also create a helper vma_is_special() (or some
other name) which would do ((vma->vm_flags & VM_SPECIAL) || vma_is_dax(vma)
|| is_vm_hugetlb_page(vma)) and then use it in all those places?
Honza
> diff --git a/mm/ksm.c b/mm/ksm.c
> index 15dd7415f7b3..787dfe4f3d44 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -2358,6 +2358,9 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
> VM_HUGETLB | VM_MIXEDMAP))
> return 0; /* just ignore the advice */
>
> + if (vma_is_dax(vma))
> + return 0;
> +
> #ifdef VM_SAO
> if (*vm_flags & VM_SAO)
> return 0;
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 21261ff0466f..40344d43e565 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -95,7 +95,7 @@ static long madvise_behavior(struct vm_area_struct *vma,
> new_flags |= VM_DONTDUMP;
> break;
> case MADV_DODUMP:
> - if (new_flags & VM_SPECIAL) {
> + if (vma_is_dax(vma) || (new_flags & VM_SPECIAL)) {
> error = -EINVAL;
> goto out;
> }
> diff --git a/mm/memory.c b/mm/memory.c
> index ec4e15494901..771acaf54fe6 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -830,6 +830,8 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
> return vma->vm_ops->find_special_page(vma, addr);
> if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
> return NULL;
> + if (pte_devmap(pte))
> + return NULL;
> if (is_zero_pfn(pfn))
> return NULL;
>
> @@ -917,6 +919,8 @@ struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
> }
> }
>
> + if (pmd_devmap(pmd))
> + return NULL;
> if (is_zero_pfn(pfn))
> return NULL;
> if (unlikely(pfn > highest_memmap_pfn))
> @@ -1227,7 +1231,7 @@ int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
> * efficient than faulting.
> */
> if (!(vma->vm_flags & (VM_HUGETLB | VM_PFNMAP | VM_MIXEDMAP)) &&
> - !vma->anon_vma)
> + !vma->anon_vma && !vma_is_dax(vma))
> return 0;
>
> if (is_vm_hugetlb_page(vma))
> @@ -1896,12 +1900,24 @@ int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
> }
> EXPORT_SYMBOL(vm_insert_pfn_prot);
>
> +static bool vm_mixed_ok(struct vm_area_struct *vma, pfn_t pfn)
> +{
> + /* these checks mirror the abort conditions in vm_normal_page */
> + if (vma->vm_flags & VM_MIXEDMAP)
> + return true;
> + if (pfn_t_devmap(pfn))
> + return true;
> + if (is_zero_pfn(pfn_t_to_pfn(pfn)))
> + return true;
> + return false;
> +}
> +
> static int __vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
> pfn_t pfn, bool mkwrite)
> {
> pgprot_t pgprot = vma->vm_page_prot;
>
> - BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));
> + BUG_ON(!vm_mixed_ok(vma, pfn));
>
> if (addr < vma->vm_start || addr >= vma->vm_end)
> return -EFAULT;
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 6954c1435833..179a84a311f6 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2927,7 +2927,8 @@ int migrate_vma(const struct migrate_vma_ops *ops,
> /* Sanity check the arguments */
> start &= PAGE_MASK;
> end &= PAGE_MASK;
> - if (!vma || is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL))
> + if (!vma || is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)
> + || vma_is_dax(dma))
> return -EINVAL;
> if (start < vma->vm_start || start >= vma->vm_end)
> return -EINVAL;
> diff --git a/mm/mlock.c b/mm/mlock.c
> index dfc6f1912176..4d009350893f 100644
> --- a/mm/mlock.c
> +++ b/mm/mlock.c
> @@ -520,7 +520,8 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
> vm_flags_t old_flags = vma->vm_flags;
>
> if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
> - is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
> + is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
> + vma_is_dax(vma))
> /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
> goto out;
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 680506faceae..2f3971a051c6 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1723,7 +1723,8 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
> vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
> if (vm_flags & VM_LOCKED) {
> if (!((vm_flags & VM_SPECIAL) || is_vm_hugetlb_page(vma) ||
> - vma == get_gate_vma(current->mm)))
> + vma == get_gate_vma(current->mm) ||
> + vma_is_dax(vma)))
> mm->locked_vm += (len >> PAGE_SHIFT);
> else
> vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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