[PATCH 4.0 10/72] Revert "MIPS: Remove race window in page fault handling"

Greg Kroah-Hartman
2015-05-11T17:55:44Z

From: Lars Persson <lars.persson@axis.com>

Commit 5b9593f3bccb9904f260f9ad7f184e1d2921bd1e upstream.

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>
Cc: linux-mips@linux-mips.org
Cc: paul.burton@imgtec.com
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/9345/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/mips/include/asm/pgtable.h | 9 +++++----
arch/mips/mm/cache.c | 27 ++++++++-------------------
2 files changed, 13 insertions(+), 23 deletions(-)

--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -127,10 +127,6 @@ 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))
@@ -154,6 +150,7 @@ static inline void set_pte(pte_t *ptep,
}
}
}
+#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 +189,7 @@ static inline void set_pte(pte_t *ptep,
}
#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 +405,15 @@ static inline pte_t pte_modify(pte_t pte

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,
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -119,36 +119,25 @@ void __flush_anon_page(struct page *page

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);