zram: clear disk io accounting when reset zram device

Clear zram disk io accounting when resetting the zram device.  Otherwise
the residual io accounting stat will affect the diskstat in the next
zram active cycle.
Signed-off-by: NWeijie Yang <weijie.yang@samsung.com>
Acked-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/block/zram/zram_drv.c

@@ -805,7 +805,9 @@ static void zram_reset_device(struct zram *zram)
 	memset(&zram->stats, 0, sizeof(zram->stats));
 	zram->disksize = 0;
 	zram->max_comp_streams = 1;
+
 	set_capacity(zram->disk, 0);
+	part_stat_set_all(&zram->disk->part0, 0);
 
 	up_write(&zram->init_lock);
 	/* I/O operation under all of CPU are done so let's free */