zram: don't return errors from read_from_bdev_async

bio_alloc will never return a NULL bio when it is allowed to sleep, and
adding a single page to bio with a single vector also can't fail, so
switch to the asserting __bio_add_page variant and drop the error returns.

Link: https://lkml.kernel.org/r/20230411171459.567614-16-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/block/zram/zram_drv.c

@@ -585,32 +585,23 @@ static void zram_page_end_io(struct bio *bio)
 	bio_put(bio);
 }
 
-/*
- * Returns 1 if the submission is successful.
- */
-static int read_from_bdev_async(struct zram *zram, struct page *page,
+static void read_from_bdev_async(struct zram *zram, struct page *page,
 			unsigned long entry, struct bio *parent)
 {
 	struct bio *bio;
 
 	bio = bio_alloc(zram->bdev, 1, parent ? parent->bi_opf : REQ_OP_READ,
 			GFP_NOIO);
-	if (!bio)
-		return -ENOMEM;
 
 	bio->bi_iter.bi_sector = entry * (PAGE_SIZE >> 9);
-	if (!bio_add_page(bio, page, PAGE_SIZE, 0)) {
-		bio_put(bio);
-		return -EIO;
-	}
+	__bio_add_page(bio, page, PAGE_SIZE, 0);
 
 	if (!parent)
 		bio->bi_end_io = zram_page_end_io;
 	else
 		bio_chain(bio, parent);
 
 	submit_bio(bio);
-	return 1;
 }
 
 #define PAGE_WB_SIG "page_index="
@@ -840,7 +831,8 @@ static int read_from_bdev(struct zram *zram, struct page *page,
 			return -EIO;
 		return read_from_bdev_sync(zram, page, entry, parent);
 	}
-	return read_from_bdev_async(zram, page, entry, parent);
+	read_from_bdev_async(zram, page, entry, parent);
+	return 1;
 }
 #else
 static inline void reset_bdev(struct zram *zram) {};