From: akpm@linux-foundation.org Subject: [patch 07/19] revert "percpu_counter: new function percpu_counter_sum_and_set" Date: Tue, 09 Dec 2008 13:14:14 -0800 Message-ID: <200812092114.mB9LEFOe027046@imap1.linux-foundation.org> Cc: akpm@linux-foundation.org, a.p.zijlstra@chello.nl, cmm@us.ibm.com, dada1@cosmosbay.com, davem@davemloft.net, linux-ext4@vger.kernel.org, stable@kernel.org To: torvalds@linux-foundation.org Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:58972 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754129AbYLIVOf (ORCPT ); Tue, 9 Dec 2008 16:14:35 -0500 Sender: linux-ext4-owner@vger.kernel.org List-ID: From: Andrew Morton Revert commit e8ced39d5e8911c662d4d69a342b9d053eaaac4e Author: Mingming Cao 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 Cc: "David S. Miller" Cc: Peter Zijlstra Cc: Mingming Cao Cc: Cc: [2.6.27.x] Signed-off-by: Andrew Morton --- 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;