[PATCH] Simplify pte_offset_{map,map_nested}() on 32 bits [try #2]

[PATCH] Simplify pte_offset_{map,map_nested}() on 32 bits [try #2]

[Franck Bui-Huu]

From: Franck Bui-Huu <fbuihuu@gmail.com>

Since both kernel and process page tables are never allocated in
highmem these 2 macros were doing unnecessary extra works for getting
a pte from a pmd.

This patch also clean up pte allocation functions by passing
__GFP_ZERO to alloc_pages() and by removing a useless local variable.

With this patch the size of the kernel is slighly reduced.

Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com>
---

 Hi Ralf,

 Maybe I'm missing something but it seems that page tables are
 never allocated from highmem. Please correct me if I'm wrong.
 This patch boot fine on a 32-bits platform without highmem
 though.

 This patch does not include any modifications for 64-bits
 platforms since I can't test them but this assertion
 should be more true since there's no highmem on these
 platforms. I can make another patch for such platforms if
 you think it makes sense.

 Please consider,

		Franck

 include/asm-mips/pgalloc.h    |   22 ++++++----------------
 include/asm-mips/pgtable-32.h |   13 +++++--------
 2 files changed, 11 insertions(+), 24 deletions(-)

diff --git a/include/asm-mips/pgalloc.h b/include/asm-mips/pgalloc.h
index 5685d4f..a3b9953 100644
--- a/include/asm-mips/pgalloc.h
+++ b/include/asm-mips/pgalloc.h
@@ -62,26 +62,16 @@ static inline void pgd_free(pgd_t *pgd)
 	free_pages((unsigned long)pgd, PGD_ORDER);
 }
 
-static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm,
-	unsigned long address)
+static inline pte_t *
+pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
 {
-	pte_t *pte;
-
-	pte = (pte_t *) __get_free_pages(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO, PTE_ORDER);
-
-	return pte;
+	return (pte_t *)__get_free_pages(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO, PTE_ORDER);
 }
 
-static inline struct page *pte_alloc_one(struct mm_struct *mm,
-	unsigned long address)
+static inline struct page *
+pte_alloc_one(struct mm_struct *mm, unsigned long address)
 {
-	struct page *pte;
-
-	pte = alloc_pages(GFP_KERNEL | __GFP_REPEAT, PTE_ORDER);
-	if (pte)
-		clear_highpage(pte);
-
-	return pte;
+	return alloc_pages(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO, PTE_ORDER);
 }
 
 static inline void pte_free_kernel(pte_t *pte)
diff --git a/include/asm-mips/pgtable-32.h b/include/asm-mips/pgtable-32.h
index 2fbd47e..9e0a8c7 100644
--- a/include/asm-mips/pgtable-32.h
+++ b/include/asm-mips/pgtable-32.h
@@ -143,6 +143,7 @@ pfn_pte(unsigned long pfn, pgprot_t prot)
 #define __pgd_offset(address)	pgd_index(address)
 #define __pud_offset(address)	(((address) >> PUD_SHIFT) & (PTRS_PER_PUD-1))
 #define __pmd_offset(address)	(((address) >> PMD_SHIFT) & (PTRS_PER_PMD-1))
+#define __pte_offset(address)	(((address) >> PAGE_SHIFT) & (PTRS_PER_PTE-1))
 
 /* to find an entry in a kernel page-table-directory */
 #define pgd_offset_k(address) pgd_offset(&init_mm, address)
@@ -153,19 +154,15 @@ pfn_pte(unsigned long pfn, pgprot_t prot)
 #define pgd_offset(mm,addr)	((mm)->pgd + pgd_index(addr))
 
 /* Find an entry in the third-level page table.. */
-#define __pte_offset(address)						\
-	(((address) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1))
 #define pte_offset(dir, address)					\
 	((pte_t *) pmd_page_vaddr(*(dir)) + __pte_offset(address))
 #define pte_offset_kernel(dir, address)					\
 	((pte_t *) pmd_page_vaddr(*(dir)) + __pte_offset(address))
 
-#define pte_offset_map(dir, address)                                    \
-	((pte_t *)page_address(pmd_page(*(dir))) + __pte_offset(address))
-#define pte_offset_map_nested(dir, address)                             \
-	((pte_t *)page_address(pmd_page(*(dir))) + __pte_offset(address))
-#define pte_unmap(pte) ((void)(pte))
-#define pte_unmap_nested(pte) ((void)(pte))
+#define pte_offset_map(dir, address)		pte_offset_kernel(dir,address)
+#define pte_offset_map_nested(dir, address)	pte_offset_kernel(dir,address)
+#define pte_unmap(pte)				((void)(pte))
+#define pte_unmap_nested(pte)			((void)(pte))
 
 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 
-- 
1.5.1.3

Re: [PATCH] Simplify pte_offset_{map,map_nested}() on 32 bits [try #2]

[Ralf Baechle]

On Fri, May 04, 2007 at 12:57:03PM +0200, Franck Bui-Huu wrote:

> From: Franck Bui-Huu <fbuihuu@gmail.com>
> 
> Since both kernel and process page tables are never allocated in
> highmem these 2 macros were doing unnecessary extra works for getting
> a pte from a pmd.
> 
> This patch also clean up pte allocation functions by passing
> __GFP_ZERO to alloc_pages() and by removing a useless local variable.
> 
> With this patch the size of the kernel is slighly reduced.

These hook allows general mapping of pagetables, not just highmem.  On MIPS
that's useful because fancy mapping stuff allows a faster implementation of
TLB exception handlers.  That was more or less the official strategy for
the R2000.  Then the R4000 came and broke this scheme with virtual aliases
which was hard to fix back then so I had to switch to the current
pagetable and TLB reload mechanism.  If you care about the details,
take a look at Linux/MIPS 2.1.1.

The fact that getting this to work again would also allow putting pagetables
into highmem at virtually no extra effort is a nice side effect, of course.

  Ralf