f2fs: compress: add sanity check during compressed cluster read

In f2fs_read_multi_pages(), we don't have to check cluster's type
again, since overwrite or partial truncation need page lock in
cluster which has already been held by reader, so cluster's type
is stable, let's change check condition to sanity check.
Signed-off-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -2170,9 +2170,7 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
 	if (ret)
 		goto out;
 
-	/* cluster was overwritten as normal cluster */
-	if (dn.data_blkaddr != COMPRESS_ADDR)
-		goto out;
+	f2fs_bug_on(sbi, dn.data_blkaddr != COMPRESS_ADDR);
 
 	for (i = 1; i < cc->cluster_size; i++) {
 		block_t blkaddr;