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

When device-dax is operating in huge-page mode we want it to behave like hugetlbfs and report the MMU page mapping size that is being enforced by the vma. Similar to commit 31383c6 "mm, hugetlbfs: introduce ->split() to vm_operations_struct" it would be messy to teach vma_mmu_pagesize() about device-dax page mapping sizes in the same (hstate) way that hugetlbfs communicates this attribute. Instead, these patches introduce a new ->pagesize() vm operation. Link: http://lkml.kernel.org/r/151996254734.27922.15813097401404359642.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Dan Williams <[email protected]> Reported-by: Jane Chu <[email protected]> Reviewed-by: Andrew Morton <[email protected]> Cc: Benjamin Herrenschmidt <[email protected]> Cc: Michael Ellerman <[email protected]> Cc: Paul Mackerras <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
chewitt · Apr 6, 2018 · 05ea886 · 05ea886
1 parent 09135cc
commit 05ea886
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Showing 2 changed files with 12 additions and 8 deletions.
diff --git a/include/linux/mm.h b/include/linux/mm.h
@@ -390,6 +390,7 @@ struct vm_operations_struct {
 	int (*huge_fault)(struct vm_fault *vmf, enum page_entry_size pe_size);
 	void (*map_pages)(struct vm_fault *vmf,
 			pgoff_t start_pgoff, pgoff_t end_pgoff);
+	unsigned long (*pagesize)(struct vm_area_struct * area);
 
 	/* notification that a previously read-only page is about to become
 	 * writable, if an error is returned it will cause a SIGBUS */

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
@@ -637,14 +637,9 @@ EXPORT_SYMBOL_GPL(linear_hugepage_index);
  */
 unsigned long vma_kernel_pagesize(struct vm_area_struct *vma)
 {
-	struct hstate *hstate;
-
-	if (!is_vm_hugetlb_page(vma))
-		return PAGE_SIZE;
-
-	hstate = hstate_vma(vma);
-
-	return 1UL << huge_page_shift(hstate);
+	if (vma->vm_ops && vma->vm_ops->pagesize)
+		return vma->vm_ops->pagesize(vma);
+	return PAGE_SIZE;
 }
 EXPORT_SYMBOL_GPL(vma_kernel_pagesize);
 
@@ -3151,6 +3146,13 @@ static int hugetlb_vm_op_split(struct vm_area_struct *vma, unsigned long addr)
 	return 0;
 }
 
+static unsigned long hugetlb_vm_op_pagesize(struct vm_area_struct *vma)
+{
+	struct hstate *hstate = hstate_vma(vma);
+
+	return 1UL << huge_page_shift(hstate);
+}
+
 /*
  * We cannot handle pagefaults against hugetlb pages at all.  They cause
  * handle_mm_fault() to try to instantiate regular-sized pages in the
@@ -3168,6 +3170,7 @@ const struct vm_operations_struct hugetlb_vm_ops = {
 	.open = hugetlb_vm_op_open,
 	.close = hugetlb_vm_op_close,
 	.split = hugetlb_vm_op_split,
+	.pagesize = hugetlb_vm_op_pagesize,
 };
 
 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,