Staging: zram: initialize device on first read

Currently the device is initialized when first write is done to the
device. Any read attempt before the first write would fail, including
"hidden" read the user may not know about (as for example if he tries
to write a partial block).

This patch initializes the device on first request, whether read or
write.
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/zram/zram_drv.c

@@ -211,11 +211,6 @@ static void zram_read(struct zram *zram, struct bio *bio)
 	u32 index;
 	struct bio_vec *bvec;
 
-	if (unlikely(!zram->init_done)) {
-		bio_endio(bio, -ENXIO);
-		return;
-	}
-
 	zram_stat64_inc(zram, &zram->stats.num_reads);
 	index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
 
@@ -286,20 +281,15 @@ static void zram_read(struct zram *zram, struct bio *bio)
 
 static void zram_write(struct zram *zram, struct bio *bio)
 {
-	int i, ret;
+	int i;
 	u32 index;
 	struct bio_vec *bvec;
 
-	if (unlikely(!zram->init_done)) {
-		ret = zram_init_device(zram);
-		if (ret)
-			goto out;
-	}
-
 	zram_stat64_inc(zram, &zram->stats.num_writes);
 	index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
 
 	bio_for_each_segment(bvec, bio, i) {
+		int ret;
 		u32 offset;
 		size_t clen;
 		struct zobj_header *zheader;
@@ -445,6 +435,11 @@ static int zram_make_request(struct request_queue *queue, struct bio *bio)
 		return 0;
 	}
 
+	if (unlikely(!zram->init_done) && zram_init_device(zram)) {
+		bio_io_error(bio);
+		return 0;
+	}
+
 	switch (bio_data_dir(bio)) {
 	case READ:
 		zram_read(zram, bio);