Add error injection with operation slowdown

Closes #29

Author: ligurio

README.md

@@ -12,6 +12,7 @@ Supported fault injections are:
 - `errinj_noop` - replace file operation with no operation
   (similar to [libeatmydata](https://github.com/stewartsmith/libeatmydata),
   but applicable to any file operation).
+- `errinj_slowdown` - slowdown invoked file operation.
 
 ### Building
 

unreliablefs.conf.5

@@ -34,6 +34,8 @@ Send SIGKILL signal to a process that invoked file operation.
 Set random errno.
 .Xr errno 2
 limited by supported errno's.
+.It Cm errinj_slowdown
+File operation slowdown for nanoseconds specified by duration parameter.
 .El
 .Pp
 The options are:
@@ -52,6 +54,8 @@ POSIX Extended Regular Expression syntax is supported and regular expressions do
 Sets the probability in percents.
 Probability equal to 0 means that error injection will never happen.
 Probability equal to 100 means that error injection will happen on each file operation.
+.It Cm duration
+Sets the duration of file operation slowdown. Applicable to errinj_slowdown only.
 .El
 .Sh EXAMPLES
 .Bd -literal

unreliablefs_errinj.c

@@ -219,6 +219,16 @@ int error_inject(const char* path, fuse_op operation)
             fprintf(stdout, "errno '%s'\n", strerror(rc));
             rc = -rc;
             break;
+        case ERRINJ_SLOWDOWN: ;
+	    struct timespec ts = {};
+	    ts.tv_nsec = err->duration;
+            fprintf(stdout, "start of '%s' slowdown for '%d' ns\n", op_name, err->duration);
+            if (nanosleep(&ts, NULL) != 0) {
+		perror("nanosleep");
+            } else {
+		fprintf(stdout, "end of '%s' slowdown with '%d' ns\n", op_name, err->duration);
+            }
+            break;
         }
     }
 
@@ -315,6 +325,8 @@ int conf_option_handler(void* cfg, const char* section,
         err->op_regexp = strdup(value);
     } else if (strcmp(key, "probability") == 0) {
         err->probability = atoi(value);
+    } else if (strcmp(key, "duration") == 0) {
+        err->duration = atoi(value);
     } else {
         fprintf(stderr, "unknown option '%s' in configuration file\n", key);
         return 0;

unreliablefs_errinj.h

@@ -36,12 +36,14 @@ const char *errinj_name[] =
     "errinj_errno",
     "errinj_kill_caller",
     "errinj_noop",
+    "errinj_slowdown",
 };
 
 typedef enum {
     ERRINJ_ERRNO,
     ERRINJ_KILL_CALLER,
     ERRINJ_NOOP,
+    ERRINJ_SLOWDOWN,
 } errinj_type;
 
 typedef struct errinj_conf errinj_conf;
@@ -52,6 +54,7 @@ struct errinj_conf {
     char *path_regexp;
     char *errno_regexp;
     unsigned int probability;
+    unsigned int duration;
     errinj_type type;
 
     TAILQ_ENTRY(errinj_conf) entries;