arm: mm: enable HAVE_RCU_TABLE_FREE logic

In order to implement fast_get_user_pages we need to ensure that the page
table walker is protected from page table pages being freed from under it.

This patch enables HAVE_RCU_TABLE_FREE, any page table pages belonging to
address spaces with multiple users will be call_rcu_sched freed.  Meaning
that disabling interrupts will block the free and protect the fast gup
page walker.

Signed-off-by: Steve Capper <steve.capper@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dann Frazier <dann.frazier@canonical.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 36d4798..eafe6ae 100644 (file)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -62,6 +62,7 @@ config ARM
        select HAVE_PERF_EVENTS
        select HAVE_PERF_REGS
        select HAVE_PERF_USER_STACK_DUMP
+       select HAVE_RCU_TABLE_FREE if (SMP && ARM_LPAE)
        select HAVE_REGS_AND_STACK_ACCESS_API
        select HAVE_SYSCALL_TRACEPOINTS
        select HAVE_UID16

diff --git a/arch/arm/include/asm/tlb.h b/arch/arm/include/asm/tlb.h
index f1a0dac..3cadb72 100644 (file)
--- a/arch/arm/include/asm/tlb.h
+++ b/arch/arm/include/asm/tlb.h
@@ -35,12 +35,39 @@
 
 #define MMU_GATHER_BUNDLE      8
 
+#ifdef CONFIG_HAVE_RCU_TABLE_FREE
+static inline void __tlb_remove_table(void *_table)
+{
+       free_page_and_swap_cache((struct page *)_table);
+}
+
+struct mmu_table_batch {
+       struct rcu_head         rcu;
+       unsigned int            nr;
+       void                    *tables[0];
+};
+
+#define MAX_TABLE_BATCH                \
+       ((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *))
+
+extern void tlb_table_flush(struct mmu_gather *tlb);
+extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
+
+#define tlb_remove_entry(tlb, entry)   tlb_remove_table(tlb, entry)
+#else
+#define tlb_remove_entry(tlb, entry)   tlb_remove_page(tlb, entry)
+#endif /* CONFIG_HAVE_RCU_TABLE_FREE */
+
 /*
  * TLB handling.  This allows us to remove pages from the page
  * tables, and efficiently handle the TLB issues.
  */
 struct mmu_gather {
        struct mm_struct        *mm;
+#ifdef CONFIG_HAVE_RCU_TABLE_FREE
+       struct mmu_table_batch  *batch;
+       unsigned int            need_flush;
+#endif
        unsigned int            fullmm;
        struct vm_area_struct   *vma;
        unsigned long           start, end;
@@ -101,6 +128,9 @@ static inline void __tlb_alloc_page(struct mmu_gather *tlb)
 static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
 {
        tlb_flush(tlb);
+#ifdef CONFIG_HAVE_RCU_TABLE_FREE
+       tlb_table_flush(tlb);
+#endif
 }
 
 static inline void tlb_flush_mmu_free(struct mmu_gather *tlb)
@@ -129,6 +159,10 @@ tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned long start
        tlb->pages = tlb->local;
        tlb->nr = 0;
        __tlb_alloc_page(tlb);
+
+#ifdef CONFIG_HAVE_RCU_TABLE_FREE
+       tlb->batch = NULL;
+#endif
 }
 
 static inline void
@@ -205,7 +239,7 @@ static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte,
        tlb_add_flush(tlb, addr + SZ_1M);
 #endif
 
-       tlb_remove_page(tlb, pte);
+       tlb_remove_entry(tlb, pte);
 }
 
 static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp,
@@ -213,7 +247,7 @@ static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp,
 {
 #ifdef CONFIG_ARM_LPAE
        tlb_add_flush(tlb, addr);
-       tlb_remove_page(tlb, virt_to_page(pmdp));
+       tlb_remove_entry(tlb, virt_to_page(pmdp));
 #endif
 }