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[PATCH 1/2] Revert "MIPS: Remove race window in page fault handling"

To: linux-mips@linux-mips.org, ralf@linux-mips.org, paul.burton@imgtec.com
Subject: [PATCH 1/2] Revert "MIPS: Remove race window in page fault handling"
From: Lars Persson <lars.persson@axis.com>
Date: Thu, 26 Feb 2015 14:16:02 +0100
Cc: linux-kernel@vger.kernel.org, Lars Persson <larper@axis.com>
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Revert commit 2a4a8b1e5d9d ("MIPS: Remove race window in page fault
handling") because it increased the number of flushed dcache pages and
became a performance problem for some workloads.

Signed-off-by: Lars Persson <larper@axis.com>
---
 arch/mips/include/asm/pgtable.h |   10 ++++++----
 arch/mips/mm/cache.c            |   27 ++++++++-------------------
 2 files changed, 14 insertions(+), 23 deletions(-)

diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
index bef782c..bd6d1cf 100644
--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -127,12 +127,9 @@ do {                                                       
                \
        }                                                               \
 } while(0)
 
-
-extern void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
-       pte_t pteval);
-
 #if defined(CONFIG_PHYS_ADDR_T_64BIT) && defined(CONFIG_CPU_MIPS32)
 
+
 #define pte_none(pte)          (!(((pte).pte_low | (pte).pte_high) & 
~_PAGE_GLOBAL))
 #define pte_present(pte)       ((pte).pte_low & _PAGE_PRESENT)
 
@@ -154,6 +151,7 @@ static inline void set_pte(pte_t *ptep, pte_t pte)
                }
        }
 }
+#define set_pte_at(mm, addr, ptep, pteval) set_pte(ptep, pteval)
 
 static inline void pte_clear(struct mm_struct *mm, unsigned long addr, pte_t 
*ptep)
 {
@@ -192,6 +190,7 @@ static inline void set_pte(pte_t *ptep, pte_t pteval)
        }
 #endif
 }
+#define set_pte_at(mm, addr, ptep, pteval) set_pte(ptep, pteval)
 
 static inline void pte_clear(struct mm_struct *mm, unsigned long addr, pte_t 
*ptep)
 {
@@ -407,12 +406,15 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t 
newprot)
 
 extern void __update_tlb(struct vm_area_struct *vma, unsigned long address,
        pte_t pte);
+extern void __update_cache(struct vm_area_struct *vma, unsigned long address,
+       pte_t pte);
 
 static inline void update_mmu_cache(struct vm_area_struct *vma,
        unsigned long address, pte_t *ptep)
 {
        pte_t pte = *ptep;
        __update_tlb(vma, address, pte);
+       __update_cache(vma, address, pte);
 }
 
 static inline void update_mmu_cache_pmd(struct vm_area_struct *vma,
diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
index 7e3ea77..f7b91d3 100644
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -119,36 +119,25 @@ void __flush_anon_page(struct page *page, unsigned long 
vmaddr)
 
 EXPORT_SYMBOL(__flush_anon_page);
 
-static void mips_flush_dcache_from_pte(pte_t pteval, unsigned long address)
+void __update_cache(struct vm_area_struct *vma, unsigned long address,
+       pte_t pte)
 {
        struct page *page;
-       unsigned long pfn = pte_pfn(pteval);
+       unsigned long pfn, addr;
+       int exec = (vma->vm_flags & VM_EXEC) && !cpu_has_ic_fills_f_dc;
 
+       pfn = pte_pfn(pte);
        if (unlikely(!pfn_valid(pfn)))
                return;
-
        page = pfn_to_page(pfn);
        if (page_mapping(page) && Page_dcache_dirty(page)) {
-               unsigned long page_addr = (unsigned long) page_address(page);
-
-               if (!cpu_has_ic_fills_f_dc ||
-                   pages_do_alias(page_addr, address & PAGE_MASK))
-                       flush_data_cache_page(page_addr);
+               addr = (unsigned long) page_address(page);
+               if (exec || pages_do_alias(addr, address & PAGE_MASK))
+                       flush_data_cache_page(addr);
                ClearPageDcacheDirty(page);
        }
 }
 
-void set_pte_at(struct mm_struct *mm, unsigned long addr,
-        pte_t *ptep, pte_t pteval)
-{
-        if (cpu_has_dc_aliases || !cpu_has_ic_fills_f_dc) {
-                if (pte_present(pteval))
-                        mips_flush_dcache_from_pte(pteval, addr);
-        }
-
-        set_pte(ptep, pteval);
-}
-
 unsigned long _page_cachable_default;
 EXPORT_SYMBOL(_page_cachable_default);
 
-- 
1.7.10.4


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