Re: [PATCH 0/5] Rewrite Motorola MMU page-table layout

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On Fri, Jan 31, 2020 at 09:38:13AM +0000, Will Deacon wrote:

This series breaks compilation for the ColdFire (with MMU) variant of
the m68k family:

That's like the same I had reported by the build robots for sun3, which
I fixed by frobbing pgtable_t. That said, this is probably a more
consistent change.

One note below:


-static inline struct page *pte_alloc_one(struct mm_struct *mm)
+static inline pgtable_t pte_alloc_one(struct mm_struct *mm)
 {
 	struct page *page = alloc_pages(GFP_DMA, 0);
 	pte_t *pte;
@@ -54,20 +55,19 @@ static inline struct page *pte_alloc_one(struct mm_struct *mm)
 		return NULL;
 	}
 
-	pte = kmap(page);
-	if (pte) {
-		clear_page(pte);
-		__flush_page_to_ram(pte);
-		flush_tlb_kernel_page(pte);
-		nocache_page(pte);
-	}
-	kunmap(page);
+	pte = page_address(page);
+	clear_page(pte);
+	__flush_page_to_ram(pte);
+	flush_tlb_kernel_page(pte);
+	nocache_page(pte);

See how it does the nocache dance ^

 
-	return page;
+	return pte;
 }
 
-static inline void pte_free(struct mm_struct *mm, struct page *page)
+static inline void pte_free(struct mm_struct *mm, pgtable_t pgtable)
 {
+	struct page *page = virt_to_page(pgtable);
+

but never sets it cached again!

 	pgtable_pte_page_dtor(page);
 	__free_page(page);
 }

Also, the alloc_one_kernel() also suspicioudly doesn't do the nocache
thing.

So either, alloc_one() shouldn't either, or it's all buggered.



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