error-injection: Add injectable error types

Add injectable error types for each error-injectable function.

One motivation of error injection test is to find software flaws,
mistakes or mis-handlings of expectable errors. If we find such
flaws by the test, that is a program bug, so we need to fix it.

But if the tester miss input the error (e.g. just return success
code without processing anything), it causes unexpected behavior
even if the caller is correctly programmed to handle any errors.
That is not what we want to test by error injection.

To clarify what type of errors the caller must expect for each
injectable function, this introduces injectable error types:

 - EI_ETYPE_NULL : means the function will return NULL if it
		    fails. No ERR_PTR, just a NULL.
 - EI_ETYPE_ERRNO : means the function will return -ERRNO
		    if it fails.
 - EI_ETYPE_ERRNO_NULL : means the function will return -ERRNO
		       (ERR_PTR) or NULL.

ALLOW_ERROR_INJECTION() macro is expanded to get one of
NULL, ERRNO, ERRNO_NULL to record the error type for
each function. e.g.

 ALLOW_ERROR_INJECTION(open_ctree, ERRNO)

This error types are shown in debugfs as below.

  ====
  / # cat /sys/kernel/debug/error_injection/list
  open_ctree [btrfs]	ERRNO
  io_ctl_init [btrfs]	ERRNO
  ====

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 2 insertions, 2 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 9798e21ebe9d..83e2349e1362 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3124,7 +3124,7 @@ recovery_tree_root:
 		goto fail_block_groups;
 	goto retry_root_backup;
 }
-ALLOW_ERROR_INJECTION(open_ctree);
+ALLOW_ERROR_INJECTION(open_ctree, ERRNO);
 
 static void btrfs_end_buffer_write_sync(struct buffer_head *bh, int uptodate)
 {
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index ef847699031a..586bb06472bb 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -333,7 +333,7 @@ static int io_ctl_init(struct btrfs_io_ctl *io_ctl, struct inode *inode,
 
 	return 0;
 }
-ALLOW_ERROR_INJECTION(io_ctl_init);
+ALLOW_ERROR_INJECTION(io_ctl_init, ERRNO);
 
 static void io_ctl_free(struct btrfs_io_ctl *io_ctl)
 {