revert "percpu_counter: new function percpu_counter_sum_and_set"
Andrew Morton [Tue, 9 Dec 2008 21:14:14 +0000 (13:14 -0800)]
Revert

    commit e8ced39d5e8911c662d4d69a342b9d053eaaac4e
    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>

fs/ext4/balloc.c
include/linux/percpu_counter.h
lib/percpu_counter.c

index c17f69b..db35cfd 100644 (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) <
                                                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",
index 2083888..9007ccd 100644 (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_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)
index dba1530..b255b93 100644 (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
  * 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_counter *fbc, int set)
        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;
 }