From 6035182b900cd667517b669962412179a08d0e1b Mon Sep 17 00:00:00 2001
From: Sergey Bronnikov <estetus@gmail.com>
Date: Mon, 9 Aug 2021 21:54:30 +0300
Subject: [PATCH] Add fault injection with 1-byte reads

Closes #86
---
 README.md             | 2 ++
 unreliablefs.conf.5   | 4 ++++
 unreliablefs_errinj.c | 7 +++++++
 unreliablefs_errinj.h | 1 +
 unreliablefs_ops.c    | 2 ++
 5 files changed, 16 insertions(+)

diff --git a/README.md b/README.md
index cb76719..241b8d1 100644
--- a/README.md
+++ b/README.md
@@ -13,6 +13,8 @@ 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 returned by `read()` call is always
+  limited by a single byte.
 
 ### Building
 
diff --git a/unreliablefs.conf.5 b/unreliablefs.conf.5
index 624bc25..20b828a 100644
--- a/unreliablefs.conf.5
+++ b/unreliablefs.conf.5
@@ -36,6 +36,10 @@ 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
+.Xr read 2
+operation.
 .El
 .Pp
 The options are:
diff --git a/unreliablefs_errinj.c b/unreliablefs_errinj.c
index a069f4d..681de37 100644
--- a/unreliablefs_errinj.c
+++ b/unreliablefs_errinj.c
@@ -21,6 +21,7 @@ const char *errinj_name[] =
     "errinj_kill_caller",
     "errinj_noop",
     "errinj_slowdown",
+    "errinj_1byte_read",
 };
 
 typedef enum {
@@ -28,6 +29,7 @@ typedef enum {
     ERRINJ_KILL_CALLER,
     ERRINJ_NOOP,
     ERRINJ_SLOWDOWN,
+    ERRINJ_1BYTE_READ,
 } errinj_type;
 
 typedef struct errinj_conf errinj_conf;
@@ -262,6 +264,11 @@ 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;
         }
     }
 
diff --git a/unreliablefs_errinj.h b/unreliablefs_errinj.h
index 299d502..4889de8 100644
--- a/unreliablefs_errinj.h
+++ b/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);
diff --git a/unreliablefs_ops.c b/unreliablefs_ops.c
index 2e6f33d..50d8715 100644
--- a/unreliablefs_ops.c
+++ b/unreliablefs_ops.c
@@ -319,6 +319,8 @@ int unreliable_read(const char *path, char *buf, size_t size, off_t offset,
     int ret = error_inject(path, OP_READ);
     if (ret == -ERRNO_NOOP) {
         return 0;
+    } else if (ret == -ERRNO_1BYTE_READ) {
+        size = 1;
     } else if (ret) {
         return ret;
     }