staging: zram: fix zram locking

Currently init_lock only prevents concurrent execution of zram_init_device()
and zram_reset_device() but not zram_make_request() nor sysfs store functions.

This patch changes init_lock into a rw_semaphore. A write lock is taken by
init, reset and store functions, a read lock is taken by zram_make_request().
Also, avoids to release the lock before calling __zram_reset_device() for
cleaning after a failed init, thus preventing any concurrent task to see an
inconsistent state of zram.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 12 insertions, 6 deletions

diff --git a/drivers/staging/zram/zram_sysfs.c b/drivers/staging/zram/zram_sysfs.c
index df1f9dc..0ea8ed2 100644
--- a/drivers/staging/zram/zram_sysfs.c
+++ b/drivers/staging/zram/zram_sysfs.c
@@ -55,19 +55,23 @@ static ssize_t disksize_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t len)
 {
 	int ret;
+	u64 disksize;
 	struct zram *zram = dev_to_zram(dev);
 
+	ret = strict_strtoull(buf, 10, &disksize);
+	if (ret)
+		return ret;
+
+	down_write(&zram->init_lock);
 	if (zram->init_done) {
+		up_write(&zram->init_lock);
 		pr_info("Cannot change disksize for initialized device\n");
 		return -EBUSY;
 	}
 
-	ret = strict_strtoull(buf, 10, &zram->disksize);
-	if (ret)
-		return ret;
-
-	zram->disksize = PAGE_ALIGN(zram->disksize);
+	zram->disksize = PAGE_ALIGN(disksize);
 	set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
+	up_write(&zram->init_lock);
 
 	return len;
 }
@@ -106,8 +110,10 @@ static ssize_t reset_store(struct device *dev,
 	if (bdev)
 		fsync_bdev(bdev);
 
+	down_write(&zram->init_lock);
 	if (zram->init_done)
-		zram_reset_device(zram);
+		__zram_reset_device(zram);
+	up_write(&zram->init_lock);
 
 	return len;
 }