[PATCH] zram: fix incorrectly stat with failed_reads

[Chao Yu <chao2.yu@samsung.com>]

Since we allocate a temporary buffer in zram_bvec_read to handle partial page
operations in this commit 924bd88d703e53d30f393fac6117f8f1bc79aab6 (Staging:
zram: allow partial page operations), our ->failed_reads value may be incorrect
as we do not increase its value when failed to allocate the temporary buffer.

Let's fix this issue and correct the annotation of failed_reads.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
---
 drivers/block/zram/zram_drv.c | 1 +
 drivers/block/zram/zram_drv.h | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index dfa4024..bf8ea1b 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -413,6 +413,7 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 
 	if (!uncmem) {
 		pr_info("Unable to allocate temp memory\n");
+		atomic64_inc(&zram->stats.failed_reads);
 		ret = -ENOMEM;
 		goto out_cleanup;
 	}
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 5b0afde..e0f725c 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -84,7 +84,7 @@ struct zram_stats {
 	atomic64_t compr_data_size;	/* compressed size of pages stored */
 	atomic64_t num_reads;	/* failed + successful */
 	atomic64_t num_writes;	/* --do-- */
-	atomic64_t failed_reads;	/* should NEVER! happen */
+	atomic64_t failed_reads;	/* can happen when memory is too low */
 	atomic64_t failed_writes;	/* can happen when memory is too low */
 	atomic64_t invalid_io;	/* non-page-aligned I/O requests */
 	atomic64_t notify_free;	/* no. of swap slot free notifications */
-- 
2.0.1.474.g72c7794