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 updates the global counter after accounting.  Since we are
   7 taking the fbc->lock to calculate the precise value of the counter in
   8 percpu_counter_sum() anyway, it should simply set fbc->count too, as the
   9 percpu_counter_sum_and_set() does.
  10
  11 This patch merge these two interfaces into one.
  12
  13 Signed-off-by: Mingming Cao <cmm@us.ibm.com>
  14 Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
  15 Cc: <linux-ext4@vger.kernel.org>
  16 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  17 Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
  18 ---
  19  fs/ext4/balloc.c               |    2 +-
  20  include/linux/percpu_counter.h |   12 +++---------
  21  lib/percpu_counter.c           |    8 +++-----
  22  3 files changed, 7 insertions(+), 15 deletions(-)
  23
  24 Index: linux-2.6.27-rc3/fs/ext4/balloc.c
  25 ===================================================================
  26 --- linux-2.6.27-rc3.orig/fs/ext4/balloc.c      2008-08-20 17:25:35.000000000 -0700
  27 +++ linux-2.6.27-rc3/fs/ext4/balloc.c   2008-08-21 14:34:32.000000000 -0700
  28 @@ -1624,7 +1624,7 @@
  29  #ifdef CONFIG_SMP
  30         if (free_blocks - root_blocks < FBC_BATCH)
  31                 free_blocks =
  32 -                       percpu_counter_sum_and_set(&sbi->s_freeblocks_counter);
  33 +                       percpu_counter_sum(&sbi->s_freeblocks_counter);
  34  #endif
  35         if (free_blocks <= root_blocks)
  36                 /* we don't have free space */
  37 Index: linux-2.6.27-rc3/include/linux/percpu_counter.h
  38 ===================================================================
  39 --- linux-2.6.27-rc3.orig/include/linux/percpu_counter.h        2008-08-20 17:25:35.000000000 -0700
  40 +++ linux-2.6.27-rc3/include/linux/percpu_counter.h     2008-08-21 14:34:32.000000000 -0700
  41 @@ -35,7 +35,7 @@
  42  void percpu_counter_destroy(struct percpu_counter *fbc);
  43  void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
  44  void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch);
  45 -s64 __percpu_counter_sum(struct percpu_counter *fbc, int set);
  46 +s64 __percpu_counter_sum(struct percpu_counter *fbc);
  47
  48  static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
  49  {
  50 @@ -44,19 +44,13 @@
  51
  52  static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
  53  {
  54 -       s64 ret = __percpu_counter_sum(fbc, 0);
  55 +       s64 ret = __percpu_counter_sum(fbc);
  56         return ret < 0 ? 0 : ret;
  57  }
  58
  59 -static inline s64 percpu_counter_sum_and_set(struct percpu_counter *fbc)
  60 -{
  61 -       return __percpu_counter_sum(fbc, 1);
  62 -}
  63 -
  64 -
  65  static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
  66  {
  67 -       return __percpu_counter_sum(fbc, 0);
  68 +       return __percpu_counter_sum(fbc);
  69  }
  70
  71  static inline s64 percpu_counter_read(struct percpu_counter *fbc)
  72 Index: linux-2.6.27-rc3/lib/percpu_counter.c
  73 ===================================================================
  74 --- linux-2.6.27-rc3.orig/lib/percpu_counter.c  2008-08-20 17:25:35.000000000 -0700
  75 +++ linux-2.6.27-rc3/lib/percpu_counter.c       2008-08-21 14:34:32.000000000 -0700
  76 @@ -52,7 +52,7 @@
  77   * Add up all the per-cpu counts, return the result.  This is a more accurate
  78   * but much slower version of percpu_counter_read_positive()
  79   */
  80 -s64 __percpu_counter_sum(struct percpu_counter *fbc, int set)
  81 +s64 __percpu_counter_sum(struct percpu_counter *fbc)
  82  {
  83         s64 ret;
  84         int cpu;
  85 @@ -62,11 +62,9 @@
  86         for_each_online_cpu(cpu) {
  87                 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
  88                 ret += *pcount;
  89 -               if (set)
  90 -                       *pcount = 0;
  91 +               *pcount = 0;
  92         }
  93 -       if (set)
  94 -               fbc->count = ret;
  95 +       fbc->count = ret;
  96
  97         spin_unlock(&fbc->lock);
  98         return ret;