[Precise][PATCH 1/1] Revert "zram: use zram->lock to protect zram_free_page() in swap free notify path"

[Luis Henriques]

BugLink: http://bugs.launchpad.net/bugs/1215513

This reverts commit f7c24073403a8d28064542b8e1e41424f90319a3, which was
commit 57ab048532c0d975538cebd4456491b5c34248f4 upstream.

This has been found to cause system lock ups when under high memory
pressure.

Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/staging/zram/zram_drv.c | 2 --
 drivers/staging/zram/zram_drv.h | 5 ++---
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
index 926d483..d197b3e 100644
--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/staging/zram/zram_drv.c
@@ -709,9 +709,7 @@ static void zram_slot_free_notify(struct block_device *bdev,
 	struct zram *zram;
 
 	zram = bdev->bd_disk->private_data;
-	down_write(&zram->lock);
 	zram_free_page(zram, index);
-	up_write(&zram->lock);
 	zram_stat64_inc(zram, &zram->stats.notify_free);
 }
 
diff --git a/drivers/staging/zram/zram_drv.h b/drivers/staging/zram/zram_drv.h
index 87f2fec..e5cd246 100644
--- a/drivers/staging/zram/zram_drv.h
+++ b/drivers/staging/zram/zram_drv.h
@@ -107,9 +107,8 @@ struct zram {
 	void *compress_buffer;
 	struct table *table;
 	spinlock_t stat64_lock;	/* protect 64-bit stats */
-	struct rw_semaphore lock; /* protect compression buffers, table,
-				   * 32bit stat counters against concurrent
-				   * notifications, reads and writes */
+	struct rw_semaphore lock; /* protect compression buffers and table
+				   * against concurrent read and writes */
 	struct request_queue *queue;
 	struct gendisk *disk;
 	int init_done;
-- 
1.8.3.2