udf: Fix reading of in-ICB files

After merging address space operations of normal and in-ICB files,
readahead could get called for in-ICB files which resulted in
udf_get_block() being called for these files. udf_get_block() is not
prepared to be called for in-ICB files and ends up returning garbage
results as it interprets file data as extent list. Fix the problem by
skipping readahead for in-ICB files.

Fixes: 37a8a39f ("udf: Switch to single address_space_operations")
Signed-off-by: Jan Kara <jack@suse.cz>

fs/udf/inode.c

@@ -241,6 +241,15 @@ static int udf_read_folio(struct file *file, struct folio *folio)
 
 static void udf_readahead(struct readahead_control *rac)
 {
+	struct udf_inode_info *iinfo = UDF_I(rac->mapping->host);
+
+	/*
+	 * No readahead needed for in-ICB files and udf_get_block() would get
+	 * confused for such file anyway.
+	 */
+	if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB)
+		return;
+
 	mpage_readahead(rac, udf_get_block);
 }