[PATCH v3 mm 1/2] mm: Define pte_index as macro for x86

[PATCH v3 mm 1/2] mm: Define pte_index as macro for x86

[Arjun Roy]

From: Arjun Roy <arjunroy@google.com>

pte_index() is either defined as a macro (e.g. sparc64) or as an
inlined function (e.g. x86). vm_insert_pages() depends on pte_index
but it is not defined on all platforms (e.g. m68k).

To fix compilation of vm_insert_pages() on architectures not providing
pte_index(), we perform the following fix:

0. For platforms where it is meaningful, and defined as a macro, no
    change is needed.
1. For platforms where it is meaningful and defined as an inlined
    function, and we want to use it with vm_insert_pages(), we define
    a degenerate macro of the form:  #define pte_index pte_index
2. vm_insert_pages() checks for the existence of a pte_index macro
   definition. If found, it implements a batched insert. If not found,
   it devolves to calling vm_insert_page() in a loop.

This patch implements step 1 for x86.

v3 of this patch fixes a compilation warning for an unused method.
v2 of this patch moved a macro definition to a more readable location.

Signed-off-by: Arjun Roy <arjunroy@google.com>
---
 arch/x86/include/asm/pgtable.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 7e118660bbd9..d9925b10e326 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -828,7 +828,10 @@ static inline unsigned long pmd_index(unsigned long address)
  *
  * this function returns the index of the entry in the pte page which would
  * control the given virtual address
+ *
+ * Also define macro so we can test if pte_index is defined for arch.
  */
+#define pte_index pte_index
 static inline unsigned long pte_index(unsigned long address)
 {
 	return (address >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
-- 
2.25.1.481.gfbce0eb801-goog

[PATCH v3 mm 2/2] mm: vm_insert_pages() checks if pte_index defined.

[Arjun Roy]

From: Arjun Roy <arjunroy@google.com>

pte_index() is either defined as a macro (e.g. sparc64) or as an
inlined function (e.g. x86). vm_insert_pages() depends on pte_index
but it is not defined on all platforms (e.g. m68k).

To fix compilation of vm_insert_pages() on architectures not providing
pte_index(), we perform the following fix:

0. For platforms where it is meaningful, and defined as a macro, no
   change is needed.
1. For platforms where it is meaningful and defined as an inlined
   function, and we want to use it with vm_insert_pages(), we define
   a degenerate macro of the form:  #define pte_index pte_index
2. vm_insert_pages() checks for the existence of a pte_index macro
   definition. If found, it implements a batched insert. If not found,
   it devolves to calling vm_insert_page() in a loop.

This patch implements step 2.

v3 of this patch fixes a compilation warning for an unused method.
v2 of this patch moved a macro definition to a more readable location.

Signed-off-by: Arjun Roy <arjunroy@google.com>
---
 mm/memory.c | 41 ++++++++++++++++++++++++++++-------------
 1 file changed, 28 insertions(+), 13 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index d6f834f7d145..47b28fcc73c2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1460,18 +1460,6 @@ static int insert_page_into_pte_locked(struct mm_struct *mm, pte_t *pte,
 	return 0;
 }
 
-static int insert_page_in_batch_locked(struct mm_struct *mm, pmd_t *pmd,
-			unsigned long addr, struct page *page, pgprot_t prot)
-{
-	int err;
-
-	if (!page_count(page))
-		return -EINVAL;
-	err = validate_page_before_insert(page);
-	return err ? err : insert_page_into_pte_locked(
-		mm, pte_offset_map(pmd, addr), addr, page, prot);
-}
-
 /*
  * This is the old fallback for page remapping.
  *
@@ -1500,8 +1488,21 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
 	return retval;
 }
 
+#ifdef pte_index
+static int insert_page_in_batch_locked(struct mm_struct *mm, pmd_t *pmd,
+			unsigned long addr, struct page *page, pgprot_t prot)
+{
+	int err;
+
+	if (!page_count(page))
+		return -EINVAL;
+	err = validate_page_before_insert(page);
+	return err ? err : insert_page_into_pte_locked(
+		mm, pte_offset_map(pmd, addr), addr, page, prot);
+}
+
 /* insert_pages() amortizes the cost of spinlock operations
- * when inserting pages in a loop.
+ * when inserting pages in a loop. Arch *must* define pte_index.
  */
 static int insert_pages(struct vm_area_struct *vma, unsigned long addr,
 			struct page **pages, unsigned long *num, pgprot_t prot)
@@ -1556,6 +1557,7 @@ static int insert_pages(struct vm_area_struct *vma, unsigned long addr,
 	*num = remaining_pages_total;
 	return ret;
 }
+#endif  /* ifdef pte_index */
 
 /**
  * vm_insert_pages - insert multiple pages into user vma, batching the pmd lock.
@@ -1575,6 +1577,7 @@ static int insert_pages(struct vm_area_struct *vma, unsigned long addr,
 int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr,
 			struct page **pages, unsigned long *num)
 {
+#ifdef pte_index
 	const unsigned long end_addr = addr + (*num * PAGE_SIZE) - 1;
 
 	if (addr < vma->vm_start || end_addr >= vma->vm_end)
@@ -1586,6 +1589,18 @@ int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr,
 	}
 	/* Defer page refcount checking till we're about to map that page. */
 	return insert_pages(vma, addr, pages, num, vma->vm_page_prot);
+#else
+	unsigned long idx = 0, pgcount = *num;
+	int err;
+
+	for (; idx < pgcount; ++idx) {
+		err = vm_insert_page(vma, addr + (PAGE_SIZE * idx), pages[idx]);
+		if (err)
+			break;
+	}
+	*num = pgcount - idx;
+	return err;
+#endif  /* ifdef pte_index */
 }
 EXPORT_SYMBOL(vm_insert_pages);
 
-- 
2.25.1.481.gfbce0eb801-goog

Re: [PATCH v3 mm 2/2] mm: vm_insert_pages() checks if pte_index defined.

[Jason Gunthorpe]

On Thu, Feb 27, 2020 at 09:47:14PM -0800, Arjun Roy wrote:
> diff --git a/mm/memory.c b/mm/memory.c
> index d6f834f7d145..47b28fcc73c2 100644
> +++ b/mm/memory.c
> @@ -1460,18 +1460,6 @@ static int insert_page_into_pte_locked(struct mm_struct *mm, pte_t *pte,
>  	return 0;
>  }
>  
> -static int insert_page_in_batch_locked(struct mm_struct *mm, pmd_t *pmd,
> -			unsigned long addr, struct page *page, pgprot_t prot)
> -{
> -	int err;
> -
> -	if (!page_count(page))
> -		return -EINVAL;
> -	err = validate_page_before_insert(page);
> -	return err ? err : insert_page_into_pte_locked(
> -		mm, pte_offset_map(pmd, addr), addr, page, prot);
> -}
> -
>  /*
>   * This is the old fallback for page remapping.
>   *
> @@ -1500,8 +1488,21 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
>  	return retval;
>  }
>  
> +#ifdef pte_index

It seems a bit weird like this, don't we usually do this kind of stuff
with some CONFIG_ARCH_HAS_XX thing?

IMHO all arches should implement pte_index as the static inline, that
has been the general direction lately.

Jason

Re: [PATCH v3 mm 2/2] mm: vm_insert_pages() checks if pte_index defined.

[Soheil Hassas Yeganeh]

On Fri, Feb 28, 2020 at 8:38 AM Jason Gunthorpe <jgg@ziepe.ca> wrote:
>
> On Thu, Feb 27, 2020 at 09:47:14PM -0800, Arjun Roy wrote:
> > diff --git a/mm/memory.c b/mm/memory.c
> > index d6f834f7d145..47b28fcc73c2 100644
> > +++ b/mm/memory.c
> > @@ -1460,18 +1460,6 @@ static int insert_page_into_pte_locked(struct mm_struct *mm, pte_t *pte,
> >       return 0;
> >  }
> >
> > -static int insert_page_in_batch_locked(struct mm_struct *mm, pmd_t *pmd,
> > -                     unsigned long addr, struct page *page, pgprot_t prot)
> > -{
> > -     int err;
> > -
> > -     if (!page_count(page))
> > -             return -EINVAL;
> > -     err = validate_page_before_insert(page);
> > -     return err ? err : insert_page_into_pte_locked(
> > -             mm, pte_offset_map(pmd, addr), addr, page, prot);
> > -}
> > -
> >  /*
> >   * This is the old fallback for page remapping.
> >   *
> > @@ -1500,8 +1488,21 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
> >       return retval;
> >  }
> >
> > +#ifdef pte_index
>
> It seems a bit weird like this, don't we usually do this kind of stuff
> with some CONFIG_ARCH_HAS_XX thing?
>
> IMHO all arches should implement pte_index as the static inline, that
> has been the general direction lately.

Based on a comment from Stephen Rothwell, we found out that "static
inline" functions are only used in tile and x86.  That's why Arjun
opted for this method to create a smaller patch-series to fix the
build breakage.

Thanks,
Soheil

> Jason