mm, powerpc: move the RCU page-table freeing into generic code

In case other architectures require RCU freed page-tables to implement
gup_fast() and software filled hashes and similar things, provide the
means to do so by moving the logic into generic code.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Requested-by: David Miller <davem@davemloft.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Tony Luck <tony.luck@intel.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

8 files changed, 22 insertions, 120 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index 8d24bacaa61e..26b0e2397a57 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -175,4 +175,7 @@ config HAVE_ARCH_JUMP_LABEL
 config HAVE_ARCH_MUTEX_CPU_RELAX
         bool
 
+config HAVE_RCU_TABLE_FREE
+        bool
+
 source "kernel/gcov/Kconfig"
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index a3128ca0fe11..423145a6f7ba 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -140,6 +140,7 @@ config PPC
         select IRQ_PER_CPU
         select GENERIC_IRQ_SHOW
         select GENERIC_IRQ_SHOW_LEVEL
+        select HAVE_RCU_TABLE_FREE if SMP
 
 config EARLY_PRINTK
         bool
diff --git a/arch/powerpc/include/asm/pgalloc.h b/arch/powerpc/include/asm/pgalloc.h
index df1b4cbb2e70..bf301ac62f35 100644
--- a/arch/powerpc/include/asm/pgalloc.h
+++ b/arch/powerpc/include/asm/pgalloc.h
@@ -31,14 +31,29 @@ static inline void pte_free(struct mm_struct *mm, pgtable_t ptepage)
 #endif
 
 #ifdef CONFIG_SMP
-extern void pgtable_free_tlb(struct mmu_gather *tlb, void *table, unsigned shift);
-extern void pte_free_finish(struct mmu_gather *tlb);
+struct mmu_gather;
+extern void tlb_remove_table(struct mmu_gather *, void *);
+
+static inline void pgtable_free_tlb(struct mmu_gather *tlb, void *table, int shift)
+{
+        unsigned long pgf = (unsigned long)table;
+        BUG_ON(shift > MAX_PGTABLE_INDEX_SIZE);
+        pgf |= shift;
+        tlb_remove_table(tlb, (void *)pgf);
+}
+
+static inline void __tlb_remove_table(void *_table)
+{
+        void *table = (void *)((unsigned long)_table & ~MAX_PGTABLE_INDEX_SIZE);
+        unsigned shift = (unsigned long)_table & MAX_PGTABLE_INDEX_SIZE;
+
+        pgtable_free(table, shift);
+}
 #else /* CONFIG_SMP */
 static inline void pgtable_free_tlb(struct mmu_gather *tlb, void *table, unsigned shift)
 {
         pgtable_free(table, shift);
 }
-static inline void pte_free_finish(struct mmu_gather *tlb) { }
 #endif /* !CONFIG_SMP */
 
 static inline void __pte_free_tlb(struct mmu_gather *tlb, struct page *ptepage,
diff --git a/arch/powerpc/include/asm/tlb.h b/arch/powerpc/include/asm/tlb.h
index 8f0ed7adcd12..e2b428b0f7ba 100644
--- a/arch/powerpc/include/asm/tlb.h
+++ b/arch/powerpc/include/asm/tlb.h
@@ -28,16 +28,6 @@
 #define tlb_start_vma(tlb, vma) do { } while (0)
 #define tlb_end_vma(tlb, vma)   do { } while (0)
 
-#define HAVE_ARCH_MMU_GATHER 1
-
-struct pte_freelist_batch;
-
-struct arch_mmu_gather {
-        struct pte_freelist_batch *batch;
-};
-
-#define ARCH_MMU_GATHER_INIT (struct arch_mmu_gather){ .batch = NULL, }
-
 extern void tlb_flush(struct mmu_gather *tlb);
 
 /* Get the generic bits... */
diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index 6e72788598f8..af40c8768a78 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -33,104 +33,6 @@
 
 #include "mmu_decl.h"
 
-#ifdef CONFIG_SMP
-
-/*
- * Handle batching of page table freeing on SMP. Page tables are
- * queued up and send to be freed later by RCU in order to avoid
- * freeing a page table page that is being walked without locks
- */
-
-static unsigned long pte_freelist_forced_free;
-
-struct pte_freelist_batch
-{
-        struct rcu_head rcu;
-        unsigned int    index;
-        unsigned long   tables[0];
-};
-
-#define PTE_FREELIST_SIZE \
-        ((PAGE_SIZE - sizeof(struct pte_freelist_batch)) \
-          / sizeof(unsigned long))
-
-static void pte_free_smp_sync(void *arg)
-{
-        /* Do nothing, just ensure we sync with all CPUs */
-}
-
-/* This is only called when we are critically out of memory
- * (and fail to get a page in pte_free_tlb).
- */
-static void pgtable_free_now(void *table, unsigned shift)
-{
-        pte_freelist_forced_free++;
-
-        smp_call_function(pte_free_smp_sync, NULL, 1);
-
-        pgtable_free(table, shift);
-}
-
-static void pte_free_rcu_callback(struct rcu_head *head)
-{
-        struct pte_freelist_batch *batch =
-                container_of(head, struct pte_freelist_batch, rcu);
-        unsigned int i;
-
-        for (i = 0; i < batch->index; i++) {
-                void *table = (void *)(batch->tables[i] & ~MAX_PGTABLE_INDEX_SIZE);
-                unsigned shift = batch->tables[i] & MAX_PGTABLE_INDEX_SIZE;
-
-                pgtable_free(table, shift);
-        }
-
-        free_page((unsigned long)batch);
-}
-
-static void pte_free_submit(struct pte_freelist_batch *batch)
-{
-        call_rcu_sched(&batch->rcu, pte_free_rcu_callback);
-}
-
-void pgtable_free_tlb(struct mmu_gather *tlb, void *table, unsigned shift)
-{
-        struct pte_freelist_batch **batchp = &tlb->arch.batch;
-        unsigned long pgf;
-
-        if (atomic_read(&tlb->mm->mm_users) < 2) {
-                pgtable_free(table, shift);
-                return;
-        }
-
-        if (*batchp == NULL) {
-                *batchp = (struct pte_freelist_batch *)__get_free_page(GFP_ATOMIC);
-                if (*batchp == NULL) {
-                        pgtable_free_now(table, shift);
-                        return;
-                }
-                (*batchp)->index = 0;
-        }
-        BUG_ON(shift > MAX_PGTABLE_INDEX_SIZE);
-        pgf = (unsigned long)table | shift;
-        (*batchp)->tables[(*batchp)->index++] = pgf;
-        if ((*batchp)->index == PTE_FREELIST_SIZE) {
-                pte_free_submit(*batchp);
-                *batchp = NULL;
-        }
-}
-
-void pte_free_finish(struct mmu_gather *tlb)
-{
-        struct pte_freelist_batch **batchp = &tlb->arch.batch;
-
-        if (*batchp == NULL)
-                return;
-        pte_free_submit(*batchp);
-        *batchp = NULL;
-}
-
-#endif /* CONFIG_SMP */
-
 static inline int is_exec_fault(void)
 {
         return current->thread.regs && TRAP(current->thread.regs) == 0x400;
diff --git a/arch/powerpc/mm/tlb_hash32.c b/arch/powerpc/mm/tlb_hash32.c
index d555cdb06bc8..27b863c14941 100644
--- a/arch/powerpc/mm/tlb_hash32.c
+++ b/arch/powerpc/mm/tlb_hash32.c
@@ -71,9 +71,6 @@ void tlb_flush(struct mmu_gather *tlb)
                  */
                 _tlbia();
         }
-
-        /* Push out batch of freed page tables */
-        pte_free_finish(tlb);
 }
 
 /*
diff --git a/arch/powerpc/mm/tlb_hash64.c b/arch/powerpc/mm/tlb_hash64.c
index 5c94ca34cd79..31f18207970b 100644
--- a/arch/powerpc/mm/tlb_hash64.c
+++ b/arch/powerpc/mm/tlb_hash64.c
@@ -165,9 +165,6 @@ void tlb_flush(struct mmu_gather *tlb)
                 __flush_tlb_pending(tlbbatch);
 
         put_cpu_var(ppc64_tlb_batch);
-
-        /* Push out batch of freed page tables */
-        pte_free_finish(tlb);
 }
 
 /**
diff --git a/arch/powerpc/mm/tlb_nohash.c b/arch/powerpc/mm/tlb_nohash.c
index 8eaf67d32043..0bdad3aecc67 100644
--- a/arch/powerpc/mm/tlb_nohash.c
+++ b/arch/powerpc/mm/tlb_nohash.c
@@ -299,9 +299,6 @@ EXPORT_SYMBOL(flush_tlb_range);
 void tlb_flush(struct mmu_gather *tlb)
 {
         flush_tlb_mm(tlb->mm);
-
-        /* Push out batch of freed page tables */
-        pte_free_finish(tlb);
 }
 
 /*