mm: add tlb_remove_check_page_size_change to track page size change

With commit e77b0852b551 ("mm/mmu_gather: track page size with mmu
gather and force flush if page size change") we added the ability to
force a tlb flush when the page size change in a mmu_gather loop.  We
did that by checking for a page size change every time we added a page
to mmu_gather for lazy flush/remove.  We can improve that by moving the
page size change check early and not doing it every time we add a page.

This also helps us to do tlb flush when invalidating a range covering
dax mapping.  Wrt dax mapping we don't have a backing struct page and
hence we don't call tlb_remove_page, which earlier forced the tlb flush
on page size change.  Moving the page size change check earlier means we
will do the same even for dax mapping.

We also avoid doing this check on architecture other than powerpc.

In a later patch we will remove page size check from tlb_remove_page().

Link: http://lkml.kernel.org/r/20161026084839.27299-5-aneesh.kumar@linux.vnet.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/tlb.h b/arch/powerpc/include/asm/tlb.h
index 99e1397b71da..609557569f65 100644
--- a/arch/powerpc/include/asm/tlb.h
+++ b/arch/powerpc/include/asm/tlb.h
@@ -28,6 +28,7 @@
 #define tlb_start_vma(tlb, vma)	do { } while (0)
 #define tlb_end_vma(tlb, vma)	do { } while (0)
 #define __tlb_remove_tlb_entry	__tlb_remove_tlb_entry
+#define tlb_remove_check_page_size_change tlb_remove_check_page_size_change
 
 extern void tlb_flush(struct mmu_gather *tlb);
 
@@ -46,6 +47,21 @@ static inline void __tlb_remove_tlb_entry(struct mmu_gather *tlb, pte_t *ptep,
 #endif
 }
 
+static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
+						     unsigned int page_size)
+{
+	if (!tlb->page_size)
+		tlb->page_size = page_size;
+	else if (tlb->page_size != page_size) {
+		tlb_flush_mmu(tlb);
+		/*
+		 * update the page size after flush for the new
+		 * mmu_gather.
+		 */
+		tlb->page_size = page_size;
+	}
+}
+
 #ifdef CONFIG_SMP
 static inline int mm_is_core_local(struct mm_struct *mm)
 {