percpu_counter_sum_cleanup.patch

   1 percpu counter: clean up percpu_counter_sum_and_set()
   2
   3 From: Mingming Cao <cmm@us.ibm.com>
   4
   5 percpu_counter_sum_and_set() and percpu_counter_sum() is the same except
   6 the former update the global counter after accounting.  Since we are
   7 taking the fbc->lock to calculate the precise value of the
   8 counter in percpu_counter_sum() anyway, it should simply set fbc->count
   9 too, as the percpu_counter_sum_and_set() dose.
  10
  11 This patch merge these two interfaces into one.
  12
  13 Signed-off-by: Mingming Cao <cmm@us.ibm.com>
  14 ---
  15  fs/ext4/balloc.c               |    2 +-
  16  include/linux/percpu_counter.h |   12 +++---------
  17  lib/percpu_counter.c           |    8 +++-----
  18  3 files changed, 7 insertions(+), 15 deletions(-)
  19
  20 Index: linux-2.6.27-rc3/fs/ext4/balloc.c
  21 ===================================================================
  22 --- linux-2.6.27-rc3.orig/fs/ext4/balloc.c      2008-08-20 17:25:35.000000000 -0700
  23 +++ linux-2.6.27-rc3/fs/ext4/balloc.c   2008-08-21 14:34:32.000000000 -0700
  24 @@ -1624,7 +1624,7 @@
  25  #ifdef CONFIG_SMP
  26         if (free_blocks - root_blocks < FBC_BATCH)
  27                 free_blocks =
  28 -                       percpu_counter_sum_and_set(&sbi->s_freeblocks_counter);
  29 +                       percpu_counter_sum(&sbi->s_freeblocks_counter);
  30  #endif
  31         if (free_blocks <= root_blocks)
  32                 /* we don't have free space */
  33 Index: linux-2.6.27-rc3/include/linux/percpu_counter.h
  34 ===================================================================
  35 --- linux-2.6.27-rc3.orig/include/linux/percpu_counter.h        2008-08-20 17:25:35.000000000 -0700
  36 +++ linux-2.6.27-rc3/include/linux/percpu_counter.h     2008-08-21 14:34:32.000000000 -0700
  37 @@ -35,7 +35,7 @@
  38  void percpu_counter_destroy(struct percpu_counter *fbc);
  39  void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
  40  void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch);
  41 -s64 __percpu_counter_sum(struct percpu_counter *fbc, int set);
  42 +s64 __percpu_counter_sum(struct percpu_counter *fbc);
  43
  44  static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
  45  {
  46 @@ -44,19 +44,13 @@
  47
  48  static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
  49  {
  50 -       s64 ret = __percpu_counter_sum(fbc, 0);
  51 +       s64 ret = __percpu_counter_sum(fbc);
  52         return ret < 0 ? 0 : ret;
  53  }
  54
  55 -static inline s64 percpu_counter_sum_and_set(struct percpu_counter *fbc)
  56 -{
  57 -       return __percpu_counter_sum(fbc, 1);
  58 -}
  59 -
  60 -
  61  static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
  62  {
  63 -       return __percpu_counter_sum(fbc, 0);
  64 +       return __percpu_counter_sum(fbc);
  65  }
  66
  67  static inline s64 percpu_counter_read(struct percpu_counter *fbc)
  68 Index: linux-2.6.27-rc3/lib/percpu_counter.c
  69 ===================================================================
  70 --- linux-2.6.27-rc3.orig/lib/percpu_counter.c  2008-08-20 17:25:35.000000000 -0700
  71 +++ linux-2.6.27-rc3/lib/percpu_counter.c       2008-08-21 14:34:32.000000000 -0700
  72 @@ -52,7 +52,7 @@
  73   * Add up all the per-cpu counts, return the result.  This is a more accurate
  74   * but much slower version of percpu_counter_read_positive()
  75   */
  76 -s64 __percpu_counter_sum(struct percpu_counter *fbc, int set)
  77 +s64 __percpu_counter_sum(struct percpu_counter *fbc)
  78  {
  79         s64 ret;
  80         int cpu;
  81 @@ -62,11 +62,9 @@
  82         for_each_online_cpu(cpu) {
  83                 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
  84                 ret += *pcount;
  85 -               if (set)
  86 -                       *pcount = 0;
  87 +               *pcount = 0;
  88         }
  89 -       if (set)
  90 -               fbc->count = ret;
  91 +       fbc->count = ret;
  92
  93         spin_unlock(&fbc->lock);
  94         return ret;