blkdebug: Use errp for read_config()

Use an Error variable in the read_config() function.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/blkdebug.c

@@ -271,7 +271,7 @@ static void remove_rule(BlkdebugRule *rule)
     g_free(rule);
 }
 
-static int read_config(BDRVBlkdebugState *s, const char *filename)
+static int read_config(BDRVBlkdebugState *s, const char *filename, Error **errp)
 {
     FILE *f;
     int ret;
@@ -279,11 +279,14 @@ static int read_config(BDRVBlkdebugState *s, const char *filename)
 
     f = fopen(filename, "r");
     if (f == NULL) {
+        error_setg_errno(errp, errno, "Could not read blkdebug config file");
         return -errno;
     }
 
     ret = qemu_config_parse(f, config_groups, filename);
     if (ret < 0) {
+        error_setg(errp, "Could not parse blkdebug config file");
+        ret = -EINVAL;
         goto fail;
     }
 
@@ -370,9 +373,8 @@ static int blkdebug_open(BlockDriverState *bs, QDict *options, int flags,
     /* Read rules from config file */
     config = qemu_opt_get(opts, "config");
     if (config) {
-        ret = read_config(s, config);
-        if (ret < 0) {
-            error_setg_errno(errp, -ret, "Could not read blkdebug config file");
+        ret = read_config(s, config, errp);
+        if (ret) {
             goto fail;
         }
     }