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authorVivek Goyal <vgoyal@redhat.com>2011-05-19 15:38:29 -0400
committerJens Axboe <jaxboe@fusionio.com>2011-05-20 20:34:53 +0200
commit575969a0dd3fe65c6556bcb8f87c42303326ea55 (patch)
tree0db18fa173b20076e03b5b9c4be4c31c56baa438
parent5624a4e445e2ec27582984b068d7bf7f127cee10 (diff)
blk-cgroup: Make 64bit per cpu stats safe on 32bit arch
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>
-rw-r--r--block/blk-cgroup.c27
-rw-r--r--block/blk-cgroup.h2
2 files changed, 24 insertions, 5 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 34bfcefdd92..3622518e1c2 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -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;
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index fd730a24b49..26222679809 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -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 {