quota: Make quota stat accounting lockless.

Quota stats is mostly writable data structure. Let's alloc percpu
bucket for each value.

NOTE: dqstats_read() function is racy against dqstats_{inc,dec}
and may return inconsistent value. But this is ok since absolute
accuracy is not required.

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 34 insertions, 8 deletions

diff --git a/include/linux/quota.h b/include/linux/quota.h
index b462916b2a0a..cdfde10481b7 100644
--- a/include/linux/quota.h
+++ b/include/linux/quota.h
@@ -174,6 +174,8 @@ enum {
 #include <linux/rwsem.h>
 #include <linux/spinlock.h>
 #include <linux/wait.h>
+#include <linux/percpu.h>
+#include <linux/smp.h>
 
 #include <linux/dqblk_xfs.h>
 #include <linux/dqblk_v1.h>
@@ -238,19 +240,43 @@ static inline int info_dirty(struct mem_dqinfo *info)
         return test_bit(DQF_INFO_DIRTY_B, &info->dqi_flags);
 }
 
+enum {
+        DQST_LOOKUPS,
+        DQST_DROPS,
+        DQST_READS,
+        DQST_WRITES,
+        DQST_CACHE_HITS,
+        DQST_ALLOC_DQUOTS,
+        DQST_FREE_DQUOTS,
+        DQST_SYNCS,
+        _DQST_DQSTAT_LAST
+};
+
 struct dqstats {
-        int lookups;
-        int drops;
-        int reads;
-        int writes;
-        int cache_hits;
-        int allocated_dquots;
-        int free_dquots;
-        int syncs;
+        int stat[_DQST_DQSTAT_LAST];
 };
 
+extern struct dqstats *dqstats_pcpu;
 extern struct dqstats dqstats;
 
+static inline void dqstats_inc(unsigned int type)
+{
+#ifdef CONFIG_SMP
+        per_cpu_ptr(dqstats_pcpu, smp_processor_id())->stat[type]++;
+#else
+        dqstats.stat[type]++;
+#endif
+}
+
+static inline void dqstats_dec(unsigned int type)
+{
+#ifdef CONFIG_SMP
+        per_cpu_ptr(dqstats_pcpu, smp_processor_id())->stat[type]--;
+#else
+        dqstats.stat[type]--;
+#endif
+}
+
 #define DQ_MOD_B        0       /* dquot modified since read */
 #define DQ_BLKS_B       1       /* uid/gid has been warned about blk limit */
 #define DQ_INODES_B     2       /* uid/gid has been warned about inode limit */