zram: return errors from read_from_bdev_sync

Propagate read errors to the caller instead of dropping them on the floor,
and stop returning the somewhat dangerous 1 on success from
read_from_bdev*.

Link: https://lkml.kernel.org/r/20230411171459.567614-18-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

@@ -770,6 +770,7 @@ struct zram_work {
 	struct zram *zram;
 	unsigned long entry;
 	struct page *page;
+	int error;
 };
 
 static void zram_sync_read(struct work_struct *work)
@@ -781,7 +782,7 @@ static void zram_sync_read(struct work_struct *work)
 	bio_init(&bio, zw->zram->bdev, &bv, 1, REQ_OP_READ);
 	bio.bi_iter.bi_sector = zw->entry * (PAGE_SIZE >> 9);
 	__bio_add_page(&bio, zw->page, PAGE_SIZE, 0);
-	submit_bio_wait(&bio);
+	zw->error = submit_bio_wait(&bio);
 }
 
 /*
@@ -803,7 +804,7 @@ static int read_from_bdev_sync(struct zram *zram, struct page *page,
 	flush_work(&work.work);
 	destroy_work_on_stack(&work.work);
 
-	return 1;
+	return work.error;
 }
 
 static int read_from_bdev(struct zram *zram, struct page *page,
@@ -816,7 +817,7 @@ static int read_from_bdev(struct zram *zram, struct page *page,
 		return read_from_bdev_sync(zram, page, entry);
 	}
 	read_from_bdev_async(zram, page, entry, parent);
-	return 1;
+	return 0;
 }
 #else
 static inline void reset_bdev(struct zram *zram) {};