arch/powerpc/mm/pgtable.c

   1 /*
   2  * This file contains common routines for dealing with free of page tables
   3  *
   4  *  Derived from arch/powerpc/mm/tlb_64.c:
   5  *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
   6  *
   7  *  Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
   8  *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
   9  *    Copyright (C) 1996 Paul Mackerras
  10  *
  11  *  Derived from "arch/i386/mm/init.c"
  12  *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  13  *
  14  *  Dave Engebretsen <engebret@us.ibm.com>
  15  *      Rework for PPC64 port.
  16  *
  17  *  This program is free software; you can redistribute it and/or
  18  *  modify it under the terms of the GNU General Public License
  19  *  as published by the Free Software Foundation; either version
  20  *  2 of the License, or (at your option) any later version.
  21  */
  22
  23 #include <linux/kernel.h>
  24 #include <linux/mm.h>
  25 #include <linux/init.h>
  26 #include <linux/percpu.h>
  27 #include <linux/hardirq.h>
  28 #include <asm/pgalloc.h>
  29 #include <asm/tlbflush.h>
  30 #include <asm/tlb.h>
  31
  32 static DEFINE_PER_CPU(struct pte_freelist_batch *, pte_freelist_cur);
  33 static unsigned long pte_freelist_forced_free;
  34
  35 struct pte_freelist_batch
  36 {
  37         struct rcu_head rcu;
  38         unsigned int    index;
  39         pgtable_free_t  tables[0];
  40 };
  41
  42 #define PTE_FREELIST_SIZE \
  43         ((PAGE_SIZE - sizeof(struct pte_freelist_batch)) \
  44           / sizeof(pgtable_free_t))
  45
  46 static void pte_free_smp_sync(void *arg)
  47 {
  48         /* Do nothing, just ensure we sync with all CPUs */
  49 }
  50
  51 /* This is only called when we are critically out of memory
  52  * (and fail to get a page in pte_free_tlb).
  53  */
  54 static void pgtable_free_now(pgtable_free_t pgf)
  55 {
  56         pte_freelist_forced_free++;
  57
  58         smp_call_function(pte_free_smp_sync, NULL, 1);
  59
  60         pgtable_free(pgf);
  61 }
  62
  63 static void pte_free_rcu_callback(struct rcu_head *head)
  64 {
  65         struct pte_freelist_batch *batch =
  66                 container_of(head, struct pte_freelist_batch, rcu);
  67         unsigned int i;
  68
  69         for (i = 0; i < batch->index; i++)
  70                 pgtable_free(batch->tables[i]);
  71
  72         free_page((unsigned long)batch);
  73 }
  74
  75 static void pte_free_submit(struct pte_freelist_batch *batch)
  76 {
  77         INIT_RCU_HEAD(&batch->rcu);
  78         call_rcu(&batch->rcu, pte_free_rcu_callback);
  79 }
  80
  81 void pgtable_free_tlb(struct mmu_gather *tlb, pgtable_free_t pgf)
  82 {
  83         /* This is safe since tlb_gather_mmu has disabled preemption */
  84         cpumask_t local_cpumask = cpumask_of_cpu(smp_processor_id());
  85         struct pte_freelist_batch **batchp = &__get_cpu_var(pte_freelist_cur);
  86
  87         if (atomic_read(&tlb->mm->mm_users) < 2 ||
  88             cpus_equal(tlb->mm->cpu_vm_mask, local_cpumask)) {
  89                 pgtable_free(pgf);
  90                 return;
  91         }
  92
  93         if (*batchp == NULL) {
  94                 *batchp = (struct pte_freelist_batch *)__get_free_page(GFP_ATOMIC);
  95                 if (*batchp == NULL) {
  96                         pgtable_free_now(pgf);
  97                         return;
  98                 }
  99                 (*batchp)->index = 0;
 100         }
 101         (*batchp)->tables[(*batchp)->index++] = pgf;
 102         if ((*batchp)->index == PTE_FREELIST_SIZE) {
 103                 pte_free_submit(*batchp);
 104                 *batchp = NULL;
 105         }
 106 }
 107
 108 void pte_free_finish(void)
 109 {
 110         /* This is safe since tlb_gather_mmu has disabled preemption */
 111         struct pte_freelist_batch **batchp = &__get_cpu_var(pte_freelist_cur);
 112
 113         if (*batchp == NULL)
 114                 return;
 115         pte_free_submit(*batchp);
 116         *batchp = NULL;
 117 }