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revert "percpu_counter: new function percpu_counter_sum_and_set"

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Revert

    commit e8ced39d5e
    Author: Mingming Cao <cmm@us.ibm.com>
    Date:   Fri Jul 11 19:27:31 2008 -0400

        percpu_counter: new function percpu_counter_sum_and_set

As described in

	revert "percpu counter: clean up percpu_counter_sum_and_set()"

the new percpu_counter_sum_and_set() is racy against updates to the
cpu-local accumulators on other CPUs.  Revert that change.

This means that ext4 will be slow again.  But correct.

Reported-by: Eric Dumazet <dada1@cosmosbay.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mingming Cao <cmm@us.ibm.com>
Cc: <linux-ext4@vger.kernel.org>
Cc: <stable@kernel.org>		[2.6.27.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrew Morton 2008-12-09 13:14:14 -08:00 committed by Linus Torvalds
parent 71c5576fbd
commit 02d2116887
3 changed files with 6 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
fs/ext4/balloc.c
View File

@ -609,8 +609,8 @@ int ext4_has_free_blocks(struct ext4_sb_info *sbi, s64 nblocks)
if (free_blocks - (nblocks + root_blocks + dirty_blocks) < if (free_blocks - (nblocks + root_blocks + dirty_blocks) <
EXT4_FREEBLOCKS_WATERMARK) { EXT4_FREEBLOCKS_WATERMARK) {
free_blocks = percpu_counter_sum_and_set(fbc); free_blocks = percpu_counter_sum_positive(fbc);
dirty_blocks = percpu_counter_sum_and_set(dbc); dirty_blocks = percpu_counter_sum_positive(dbc);
if (dirty_blocks < 0) { if (dirty_blocks < 0) {
printk(KERN_CRIT "Dirty block accounting " printk(KERN_CRIT "Dirty block accounting "
"went wrong %lld\n", "went wrong %lld\n",

12
include/linux/percpu_counter.h
View File

@ -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_destroy(struct percpu_counter *fbc);
void percpu_counter_set(struct percpu_counter *fbc, s64 amount); void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch); 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) 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) 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; 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) 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) static inline s64 percpu_counter_read(struct percpu_counter *fbc)

7
lib/percpu_counter.c
View File

@ -52,7 +52,7 @@ EXPORT_SYMBOL(__percpu_counter_add);
* Add up all the per-cpu counts, return the result. This is a more accurate * Add up all the per-cpu counts, return the result. This is a more accurate
* but much slower version of percpu_counter_read_positive() * 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; s64 ret;
int cpu; int cpu;
@ -62,12 +62,7 @@ s64 __percpu_counter_sum(struct percpu_counter *fbc, int set)
for_each_online_cpu(cpu) { for_each_online_cpu(cpu) {
s32 *pcount = per_cpu_ptr(fbc->counters, cpu); s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
ret += *pcount; ret += *pcount;
if (set)
*pcount = 0;
} }
if (set)
fbc->count = ret;
spin_unlock(&fbc->lock); spin_unlock(&fbc->lock);
return ret; return ret;
} }