Commit 31383c68 authored by Dan Williams's avatar Dan Williams Committed by Linus Torvalds

mm, hugetlbfs: introduce ->split() to vm_operations_struct

Patch series "device-dax: fix unaligned munmap handling"

When device-dax is operating in huge-page mode we want it to behave like
hugetlbfs and fail attempts to split vmas into unaligned ranges.  It
would be messy to teach the munmap path about device-dax alignment
constraints in the same (hstate) way that hugetlbfs communicates this
constraint.  Instead, these patches introduce a new ->split() vm

This patch (of 2):

The device-dax interface has similar constraints as hugetlbfs in that it
requires the munmap path to unmap in huge page aligned units.  Rather
than add more custom vma handling code in __split_vma() introduce a new
vm operation to perform this vma specific check.

Fixes: dee41079 ("/dev/dax, core: file operations and dax-mmap")
Signed-off-by: default avatarDan Williams <>
Cc: Jeff Moyer <>
Cc: <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 95a87982
......@@ -377,6 +377,7 @@ enum page_entry_size {
struct vm_operations_struct {
void (*open)(struct vm_area_struct * area);
void (*close)(struct vm_area_struct * area);
int (*split)(struct vm_area_struct * area, unsigned long addr);
int (*mremap)(struct vm_area_struct * area);
int (*fault)(struct vm_fault *vmf);
int (*huge_fault)(struct vm_fault *vmf, enum page_entry_size pe_size);
......@@ -3125,6 +3125,13 @@ static void hugetlb_vm_op_close(struct vm_area_struct *vma)
static int hugetlb_vm_op_split(struct vm_area_struct *vma, unsigned long addr)
if (addr & ~(huge_page_mask(hstate_vma(vma))))
return -EINVAL;
return 0;
* We cannot handle pagefaults against hugetlb pages at all. They cause
* handle_mm_fault() to try to instantiate regular-sized pages in the
......@@ -3141,6 +3148,7 @@ const struct vm_operations_struct hugetlb_vm_ops = {
.fault = hugetlb_vm_op_fault,
.open = hugetlb_vm_op_open,
.close = hugetlb_vm_op_close,
.split = hugetlb_vm_op_split,
static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
......@@ -2555,9 +2555,11 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
struct vm_area_struct *new;
int err;
if (is_vm_hugetlb_page(vma) && (addr &
return -EINVAL;
if (vma->vm_ops && vma->vm_ops->split) {
err = vma->vm_ops->split(vma, addr);
if (err)
return err;
new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
if (!new)
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