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blk-cgroup: Make 64bit per cpu stats safe on 32bit arch

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Some of the stats are 64bit and updation will be non atomic on 32bit
architecture. Use sequence counters on 32bit arch to make reading
of stats safe.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Vivek Goyal 2011-05-19 15:38:29 -04:00 committed by Jens Axboe
parent 5624a4e445
commit 575969a0dd
2 changed files with 24 additions and 5 deletions
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27
block/blk-cgroup.c
View File

@ -400,14 +400,25 @@ void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
uint64_t bytes, bool direction, bool sync)
{
struct blkio_group_stats_cpu *stats_cpu;
unsigned long flags;
/*
* Disabling interrupts to provide mutual exclusion between two
* writes on same cpu. It probably is not needed for 64bit. Not
* optimizing that case yet.
*/
local_irq_save(flags);
stats_cpu = this_cpu_ptr(blkg->stats_cpu);
u64_stats_update_begin(&stats_cpu->syncp);
stats_cpu->sectors += bytes >> 9;
blkio_add_stat(stats_cpu->stat_arr_cpu[BLKIO_STAT_CPU_SERVICED],
1, direction, sync);
blkio_add_stat(stats_cpu->stat_arr_cpu[BLKIO_STAT_CPU_SERVICE_BYTES],
bytes, direction, sync);
u64_stats_update_end(&stats_cpu->syncp);
local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(blkiocg_update_dispatch_stats);
@ -622,15 +633,21 @@ static uint64_t blkio_read_stat_cpu(struct blkio_group *blkg,
{
int cpu;
struct blkio_group_stats_cpu *stats_cpu;
uint64_t val = 0;
u64 val = 0, tval;
for_each_possible_cpu(cpu) {
unsigned int start;
stats_cpu = per_cpu_ptr(blkg->stats_cpu, cpu);
if (type == BLKIO_STAT_CPU_SECTORS)
val += stats_cpu->sectors;
else
val += stats_cpu->stat_arr_cpu[type][sub_type];
do {
start = u64_stats_fetch_begin(&stats_cpu->syncp);
if (type == BLKIO_STAT_CPU_SECTORS)
tval = stats_cpu->sectors;
else
tval = stats_cpu->stat_arr_cpu[type][sub_type];
} while(u64_stats_fetch_retry(&stats_cpu->syncp, start));
val += tval;
}
return val;

2
block/blk-cgroup.h
View File

@ -14,6 +14,7 @@
*/
#include <linux/cgroup.h>
#include <linux/u64_stats_sync.h>
enum blkio_policy_id {
BLKIO_POLICY_PROP = 0, /* Proportional Bandwidth division */
@ -154,6 +155,7 @@ struct blkio_group_stats {
struct blkio_group_stats_cpu {
uint64_t sectors;
uint64_t stat_arr_cpu[BLKIO_STAT_CPU_NR][BLKIO_STAT_TOTAL];
struct u64_stats_sync syncp;
};
struct blkio_group {