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SubjectRe: [PATCH 01/42] percpu counter: clean up percpu_counter_sum_and_set()
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On Thu, 2008-10-09 at 00:05 -0400, Theodore Ts'o wrote:
> From: Mingming Cao <cmm@us.ibm.com>
>
> percpu_counter_sum_and_set() and percpu_counter_sum() is the same except
> the former updates the global counter after accounting. Since we are
> taking the fbc->lock to calculate the precise value of the counter in
> percpu_counter_sum() anyway, it should simply set fbc->count too, as the
> percpu_counter_sum_and_set() does.
>
> This patch merge these two interfaces into one.

I totally missed the patch introducing this _and_set() horror, but this
does look like a good cleanup.

Thanks Mingming!

Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

> Signed-off-by: Mingming Cao <cmm@us.ibm.com>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: <linux-ext4@vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
> ---
> fs/ext4/balloc.c | 2 +-
> include/linux/percpu_counter.h | 12 +++---------
> lib/percpu_counter.c | 8 +++-----
> 3 files changed, 7 insertions(+), 15 deletions(-)
>
> diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
> index e9fa960..00a94d5 100644
> --- a/fs/ext4/balloc.c
> +++ b/fs/ext4/balloc.c
> @@ -1624,7 +1624,7 @@ ext4_fsblk_t ext4_has_free_blocks(struct ext4_sb_info *sbi,
> #ifdef CONFIG_SMP
> if (free_blocks - root_blocks < FBC_BATCH)
> free_blocks =
> - percpu_counter_sum_and_set(&sbi->s_freeblocks_counter);
> + percpu_counter_sum(&sbi->s_freeblocks_counter);
> #endif
> if (free_blocks <= root_blocks)
> /* we don't have free space */
> diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h
> index 2083888..9007ccd 100644
> --- a/include/linux/percpu_counter.h
> +++ b/include/linux/percpu_counter.h
> @@ -35,7 +35,7 @@ int percpu_counter_init_irq(struct percpu_counter *fbc, s64 amount);
> void percpu_counter_destroy(struct percpu_counter *fbc);
> void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
> void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch);
> -s64 __percpu_counter_sum(struct percpu_counter *fbc, int set);
> +s64 __percpu_counter_sum(struct percpu_counter *fbc);
>
> static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
> {
> @@ -44,19 +44,13 @@ static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
>
> static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
> {
> - s64 ret = __percpu_counter_sum(fbc, 0);
> + s64 ret = __percpu_counter_sum(fbc);
> return ret < 0 ? 0 : ret;
> }
>
> -static inline s64 percpu_counter_sum_and_set(struct percpu_counter *fbc)
> -{
> - return __percpu_counter_sum(fbc, 1);
> -}
> -
> -
> static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
> {
> - return __percpu_counter_sum(fbc, 0);
> + return __percpu_counter_sum(fbc);
> }
>
> static inline s64 percpu_counter_read(struct percpu_counter *fbc)
> diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
> index 4a8ba4b..a866389 100644
> --- a/lib/percpu_counter.c
> +++ b/lib/percpu_counter.c
> @@ -52,7 +52,7 @@ EXPORT_SYMBOL(__percpu_counter_add);
> * Add up all the per-cpu counts, return the result. This is a more accurate
> * but much slower version of percpu_counter_read_positive()
> */
> -s64 __percpu_counter_sum(struct percpu_counter *fbc, int set)
> +s64 __percpu_counter_sum(struct percpu_counter *fbc)
> {
> s64 ret;
> int cpu;
> @@ -62,11 +62,9 @@ s64 __percpu_counter_sum(struct percpu_counter *fbc, int set)
> for_each_online_cpu(cpu) {
> s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
> ret += *pcount;
> - if (set)
> - *pcount = 0;
> + *pcount = 0;
> }
> - if (set)
> - fbc->count = ret;
> + fbc->count = ret;
>
> spin_unlock(&fbc->lock);
> return ret;



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