btrfs: allow us to inject errors at io_ctl_init

This was instrumental in reproducing a space cache bug.
Signed-off-by: NJosef Bacik <jbacik@fb.com>
Acked-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

fs/btrfs/free-space-cache.c

@@ -22,6 +22,7 @@
 #include <linux/slab.h>
 #include <linux/math64.h>
 #include <linux/ratelimit.h>
+#include <linux/bpf.h>
 #include "ctree.h"
 #include "free-space-cache.h"
 #include "transaction.h"
@@ -332,6 +333,7 @@ static int io_ctl_init(struct btrfs_io_ctl *io_ctl, struct inode *inode,
 
 	return 0;
 }
+BPF_ALLOW_ERROR_INJECTION(io_ctl_init);
 
 static void io_ctl_free(struct btrfs_io_ctl *io_ctl)
 {