Eric Lee / linux-smarc-t335x-v3.2

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Commit 02d211688727ad02bb4555b1aa8ae2de16b21b39

Authored by Andrew Morton
Committed by Linus Torvalds
1 parent 71c5576fbd
Exists in master and in 4 other branches v3.2_AM335xPSP_04.06.00.11, v3.2_NEWT335xPSP_04.06.00.11, v3.2_SBC_SMARTMEN, v3.2_SMARCT335xPSP_04.06.00.11

revert "percpu_counter: new function percpu_counter_sum_and_set" 

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>

Showing 3 changed files with 6 additions and 17 deletions Side-by-side Diff

... ... @@ -609,8 +609,8 @@
609 609  
610 610 if (free_blocks - (nblocks + root_blocks + dirty_blocks) <
611 611 EXT4_FREEBLOCKS_WATERMARK) {
612   - free_blocks = percpu_counter_sum_and_set(fbc);
613   - dirty_blocks = percpu_counter_sum_and_set(dbc);
  612 + free_blocks = percpu_counter_sum_positive(fbc);
  613 + dirty_blocks = percpu_counter_sum_positive(dbc);
614 614 if (dirty_blocks < 0) {
615 615 printk(KERN_CRIT "Dirty block accounting "
616 616 "went wrong %lld\n",
include/linux/percpu_counter.h
Diff comments   View file @ 02d2116
... ... @@ -35,7 +35,7 @@
35 35 void percpu_counter_destroy(struct percpu_counter *fbc);
36 36 void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
37 37 void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch);
38   -s64 __percpu_counter_sum(struct percpu_counter *fbc, int set);
  38 +s64 __percpu_counter_sum(struct percpu_counter *fbc);
39 39  
40 40 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
41 41 {
42 42  
43 43  
... ... @@ -44,19 +44,13 @@
44 44  
45 45 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
46 46 {
47   - s64 ret = __percpu_counter_sum(fbc, 0);
  47 + s64 ret = __percpu_counter_sum(fbc);
48 48 return ret < 0 ? 0 : ret;
49 49 }
50 50  
51   -static inline s64 percpu_counter_sum_and_set(struct percpu_counter *fbc)
52   -{
53   - return __percpu_counter_sum(fbc, 1);
54   -}
55   -
56   -
57 51 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
58 52 {
59   - return __percpu_counter_sum(fbc, 0);
  53 + return __percpu_counter_sum(fbc);
60 54 }
61 55  
62 56 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
lib/percpu_counter.c
Diff comments   View file @ 02d2116
... ... @@ -52,7 +52,7 @@
52 52 * Add up all the per-cpu counts, return the result. This is a more accurate
53 53 * but much slower version of percpu_counter_read_positive()
54 54 */
55   -s64 __percpu_counter_sum(struct percpu_counter *fbc, int set)
  55 +s64 __percpu_counter_sum(struct percpu_counter *fbc)
56 56 {
57 57 s64 ret;
58 58 int cpu;
59 59  
... ... @@ -62,12 +62,7 @@
62 62 for_each_online_cpu(cpu) {
63 63 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
64 64 ret += *pcount;
65   - if (set)
66   - *pcount = 0;
67 65 }
68   - if (set)
69   - fbc->count = ret;
70   -
71 66 spin_unlock(&fbc->lock);
72 67 return ret;
73 68 }