From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Revert
commit e8ced39d5e8911c662d4d69a342b9d053eaaac4e
Author: Mingming Cao <cmm@xxxxxxxxxx>
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@xxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Mingming Cao <cmm@xxxxxxxxxx>
Cc: <linux-ext4@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxx> [2.6.27.x]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/ext4/balloc.c | 4 ++--
include/linux/percpu_counter.h | 12 +++---------
lib/percpu_counter.c | 7 +------
3 files changed, 6 insertions(+), 17 deletions(-)
diff -puN fs/ext4/balloc.c~revert-percpu_counter-new-function-percpu_counter_sum_and_set fs/ext4/balloc.c
--- a/fs/ext4/balloc.c~revert-percpu_counter-new-function-percpu_counter_sum_and_set
+++ a/fs/ext4/balloc.c
@@ -609,8 +609,8 @@ int ext4_has_free_blocks(struct ext4_sb_
if (free_blocks - (nblocks + root_blocks + dirty_blocks) <
EXT4_FREEBLOCKS_WATERMARK) {
- free_blocks = percpu_counter_sum_and_set(fbc);
- dirty_blocks = percpu_counter_sum_and_set(dbc);
+ free_blocks = percpu_counter_sum_positive(fbc);
+ dirty_blocks = percpu_counter_sum_positive(dbc);
if (dirty_blocks < 0) {
printk(KERN_CRIT "Dirty block accounting "
"went wrong %lld\n",
diff -puN include/linux/percpu_counter.h~revert-percpu_counter-new-function-percpu_counter_sum_and_set include/linux/percpu_counter.h
--- a/include/linux/percpu_counter.h~revert-percpu_counter-new-function-percpu_counter_sum_and_set
+++ a/include/linux/percpu_counter.h
@@ -35,7 +35,7 @@ int percpu_counter_init_irq(struct percp
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(st
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 -puN lib/percpu_counter.c~revert-percpu_counter-new-function-percpu_counter_sum_and_set lib/percpu_counter.c
--- a/lib/percpu_counter.c~revert-percpu_counter-new-function-percpu_counter_sum_and_set
+++ a/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;
@@ -62,12 +62,7 @@ s64 __percpu_counter_sum(struct percpu_c
for_each_online_cpu(cpu) {
s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
ret += *pcount;
- if (set)
- *pcount = 0;
}
- if (set)
- fbc->count = ret;
-
spin_unlock(&fbc->lock);
return ret;
}
_
--
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