ext4: properly handle error of ext4_init_block_bitmap in ext4_read_block_bitmap_nowait

We mark buffer_head of bitmap successfully initialized even error occurs
in ext4_init_block_bitmap. Although we will return error, we will get a
invalid buffer_head of bitmap from next ext4_read_block_bitmap_nowait
which is marked buffer_verified but not successfully initialized actually
in previous ext4_read_block_bitmap_nowait.
Fix this by only marking buffer_head successfully initialized if
ext4_init_block_bitmap successes.
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://lore.kernel.org/r/20230221115919.1918161-2-shikemeng@huaweicloud.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/balloc.c

@@ -474,16 +474,18 @@ ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group,
 			goto out;
 		}
 		err = ext4_init_block_bitmap(sb, bh, block_group, desc);
-		set_bitmap_uptodate(bh);
-		set_buffer_uptodate(bh);
-		set_buffer_verified(bh);
-		ext4_unlock_group(sb, block_group);
-		unlock_buffer(bh);
 		if (err) {
+			ext4_unlock_group(sb, block_group);
+			unlock_buffer(bh);
 			ext4_error(sb, "Failed to init block bitmap for group "
 				   "%u: %d", block_group, err);
 			goto out;
 		}
+		set_bitmap_uptodate(bh);
+		set_buffer_uptodate(bh);
+		set_buffer_verified(bh);
+		ext4_unlock_group(sb, block_group);
+		unlock_buffer(bh);
 		goto verify;
 	}
 	ext4_unlock_group(sb, block_group);