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

[PATCH 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.

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..6658c04bce83 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -823,6 +823,9 @@ static inline unsigned long pmd_index(unsigned long address)
  */
 #define mk_pte(page, pgprot)   pfn_pte(page_to_pfn(page), (pgprot))
 
+/* Degenerative definition so we can test if pte_index is defined for arch. */
+#define pte_index pte_index
+
 /*
  * the pte page can be thought of an array like this: pte_t[PTRS_PER_PTE]
  *
-- 
2.25.1.481.gfbce0eb801-goog

[PATCH 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.

Signed-off-by: Arjun Roy <arjunroy@google.com>

---
 mm/memory.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index d6f834f7d145..33631a5b5c3f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1500,8 +1500,9 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
 	return retval;
 }
 
+#ifdef pte_index
 /* 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 mm 1/2] mm: Define pte_index as macro for x86

[Stephen Rothwell]

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Hi Arjun,

On Thu, 27 Feb 2020 16:46:56 -0800 Arjun Roy <arjunroy.kdev@gmail.com> wrote:
>
> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
> index 7e118660bbd9..6658c04bce83 100644
> --- a/arch/x86/include/asm/pgtable.h
> +++ b/arch/x86/include/asm/pgtable.h
> @@ -823,6 +823,9 @@ static inline unsigned long pmd_index(unsigned long address)
>   */
>  #define mk_pte(page, pgprot)   pfn_pte(page_to_pfn(page), (pgprot))
>  
> +/* Degenerative definition so we can test if pte_index is defined for arch. */
> +#define pte_index pte_index

You should put this definition directly above the static inline function.

i.e.

#define pte_index pte_index
static inline unsigned long pte_index(unsigned long address)
	...

-- 
Cheers,
Stephen Rothwell

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

[Arjun Roy]

On Thu, Feb 27, 2020 at 4:57 PM Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> Hi Arjun,
>
> On Thu, 27 Feb 2020 16:46:56 -0800 Arjun Roy <arjunroy.kdev@gmail.com> wrote:
> >
> > diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
> > index 7e118660bbd9..6658c04bce83 100644
> > --- a/arch/x86/include/asm/pgtable.h
> > +++ b/arch/x86/include/asm/pgtable.h
> > @@ -823,6 +823,9 @@ static inline unsigned long pmd_index(unsigned long address)
> >   */
> >  #define mk_pte(page, pgprot)   pfn_pte(page_to_pfn(page), (pgprot))
> >
> > +/* Degenerative definition so we can test if pte_index is defined for arch. */
> > +#define pte_index pte_index
>
> You should put this definition directly above the static inline function.
>
> i.e.
>
> #define pte_index pte_index
> static inline unsigned long pte_index(unsigned long address)
>         ...
>
Done.

-Arjun

> --
> Cheers,
> Stephen Rothwell