[PATCH] staging: zcache: fix serialization bug in zv stats

In a multithreaded workload, the zv_curr_dist_counts
and zv_cumul_dist_counts statistics are being corrupted
because the increments and decrements in zv_create
and zv_free are not atomic.

This patch converts these statistics and their corresponding
increments/decrements/reads to atomic operations.

Based on v3.2-rc7

Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>

drivers/staging/zcache/zcache-main.c | 14 +++++++-
1 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
index 56c1f9c..d39bb51 100644
a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -655,8 +655,8 @@ static unsigned int zv_max_zsize = (PAGE_SIZE / 8) * 7;
*/
static unsigned int zv_max_mean_zsize = (PAGE_SIZE / 8) * 5;

-static unsigned long zv_curr_dist_counts[NCHUNKS];
-static unsigned long zv_cumul_dist_counts[NCHUNKS];
+static atomic_t zv_curr_dist_counts[NCHUNKS];
+static atomic_t zv_cumul_dist_counts[NCHUNKS];

static struct zv_hdr *zv_create(struct xv_pool *xvpool, uint32_t pool_id,
struct tmem_oid *oid, uint32_t index,
@@ -675,8 +675,8 @@ static struct zv_hdr *zv_create(struct xv_pool *xvpool, uint32_t pool_id,
&page, &offset, ZCACHE_GFP_MASK);
if (unlikely(ret))
goto out;
- zv_curr_dist_counts[chunks]++;
- zv_cumul_dist_counts[chunks]++;
+ atomic_inc(&zv_curr_dist_counts[chunks]);
+ atomic_inc(&zv_cumul_dist_counts[chunks]);
zv = kmap_atomic(page, KM_USER0) + offset;
zv->index = index;
zv->oid = *oid;
@@ -698,7 +698,7 @@ static void zv_free(struct xv_pool *xvpool, struct zv_hdr *zv)

ASSERT_SENTINEL(zv, ZVH);
BUG_ON(chunks >= NCHUNKS);
- zv_curr_dist_counts[chunks]--;
+ atomic_dec(&zv_curr_dist_counts[chunks]);
size -= sizeof(*zv);
BUG_ON(size == 0);
INVERT_SENTINEL(zv, ZVH);
@@ -738,7 +738,7 @@ static int zv_curr_dist_counts_show(char *buf)
char *p = buf;

for (i = 0; i < NCHUNKS; i++) {
- n = zv_curr_dist_counts[i];
+ n = atomic_read(&zv_curr_dist_counts[i]);
p += sprintf(p, "%lu ", n);
chunks += n;
sum_total_chunks += i * n;
@@ -754,7 +754,7 @@ static int zv_cumul_dist_counts_show(char *buf)
char *p = buf;

for (i = 0; i < NCHUNKS; i++) {
- n = zv_cumul_dist_counts[i];
+ n = atomic_read(&zv_cumul_dist_counts[i]);
p += sprintf(p, "%lu ", n);
chunks += n;
sum_total_chunks += i * n;
1.7.5.4

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