f2fs: introduce f2fs_bmap_compress()

to support bmap() on compressed inode: if queried block locates in
non-compressed cluster, return its physical block address.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -3666,6 +3666,37 @@ static int f2fs_set_data_page_dirty(struct page *page)
 	return 0;
 }
 
+
+static sector_t f2fs_bmap_compress(struct inode *inode, sector_t block)
+{
+#ifdef CONFIG_F2FS_FS_COMPRESSION
+	struct dnode_of_data dn;
+	sector_t start_idx, blknr = 0;
+	int ret;
+
+	start_idx = round_down(block, F2FS_I(inode)->i_cluster_size);
+
+	set_new_dnode(&dn, inode, NULL, NULL, 0);
+	ret = f2fs_get_dnode_of_data(&dn, start_idx, LOOKUP_NODE);
+	if (ret)
+		return 0;
+
+	if (dn.data_blkaddr != COMPRESS_ADDR) {
+		dn.ofs_in_node += block - start_idx;
+		blknr = f2fs_data_blkaddr(&dn);
+		if (!__is_valid_data_blkaddr(blknr))
+			blknr = 0;
+	}
+
+	f2fs_put_dnode(&dn);
+
+	return blknr;
+#else
+	return -EOPNOTSUPP;
+#endif
+}
+
+
 static sector_t f2fs_bmap(struct address_space *mapping, sector_t block)
 {
 	struct inode *inode = mapping->host;
@@ -3677,6 +3708,9 @@ static sector_t f2fs_bmap(struct address_space *mapping, sector_t block)
 	if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
 		filemap_write_and_wait(mapping);
 
+	if (f2fs_compressed_file(inode))
+		return f2fs_bmap_compress(inode, block);
+
 	return generic_block_bmap(mapping, block, get_data_block_bmap);
 }