Add fault injection with 1-byte reads

Closes #86

README.md

@@ -13,6 +13,7 @@ Supported fault injections are:
   (similar to [libeatmydata](https://github.com/stewartsmith/libeatmydata),
   but applicable to any file operation).
 - `errinj_slowdown` - slowdown invoked file operation.
+- `errinj_1byte_read` - amount of data `read()` is returned is limited by 1 byte.
 
 ### Building
 

unreliablefs.conf.5

@@ -36,6 +36,8 @@ Set random errno.
 limited by supported errno's.
 .It Cm errinj_slowdown
 File operation slowdown for nanoseconds specified by duration parameter.
+.It Cm errinj_1byte_read
+Return exactly 1 byte on every read() operation.
 .El
 .Pp
 The options are:

unreliablefs_errinj.c

@@ -231,6 +231,11 @@ int error_inject(const char* path, fuse_op operation)
 		fprintf(stdout, "end of '%s' slowdown with '%d' ns\n", op_name, err->duration);
             }
             break;
+        case ERRINJ_1BYTE_READ:
+            fprintf(stdout, "start of 1-byte read\n");
+            if (strcmp(op_name, "read") == 0)
+                rc = -ERRINJ_1BYTE_READ;
+            break;
         }
     }
 

unreliablefs_errinj.h

@@ -22,6 +22,7 @@
 #define MIN_PROBABLITY 0
 #define MAX_PROBABLITY 100
 #define ERRNO_NOOP -999
+#define ERRNO_1BYTE_READ -998
 #define DEFAULT_SIGNAL_NAME SIGKILL
 
 int error_inject(const char* path, fuse_op operation);
@@ -37,13 +38,15 @@ const char *errinj_name[] =
     "errinj_kill_caller",
     "errinj_noop",
     "errinj_slowdown",
+    "errinj_1byte_read",
 };
 
 typedef enum {
     ERRINJ_ERRNO,
     ERRINJ_KILL_CALLER,
     ERRINJ_NOOP,
     ERRINJ_SLOWDOWN,
+    ERRINJ_1BYTE_READ,
 } errinj_type;
 
 typedef struct errinj_conf errinj_conf;

unreliablefs_ops.c

@@ -334,6 +334,7 @@ int unreliable_read(const char *path, char *buf, size_t size, off_t offset,
 	return -errno;
     }
 
+    /* read 1 byte in a loop */
     ret = pread(fd, buf, size, offset);
     if (ret == -1) {
         ret = -errno;