Commit 02d21168 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
Browse files

revert "percpu_counter: new function percpu_counter_sum_and_set" 



Revert

    commit e8ced39d
    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: default avatarEric 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 71c5576f

fs/ext4/balloc.c

+2 −2
Original line number Diff line number Diff line
@@ -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",

include/linux/percpu_counter.h

+3 −9
Original line number Diff line number Diff line
@@ -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)

lib/percpu_counter.c

+1 −6
Original line number Diff line number Diff line
@@ -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;

}

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