From 5c57c084346fbfe6f3f45236c151ad1c83b6b398 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@fb.com>
Date: Wed, 23 Jul 2014 16:19:48 +0200
Subject: [PATCH 1/1] null: add FIO_FAKEIO flag

Tell the backend that null just fakes IO, and use this knowledge
to have verifies automagically work when using null. This allows
testing of a wider range of paths with ioengine=null.

Signed-off-by: Jens Axboe <axboe@fb.com>
---
 engines/null.c | 4 ++--
 ioengine.h     | 1 +
 verify.c       | 7 +++++++
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/engines/null.c b/engines/null.c
index eb17b113..e7df6a13 100644
--- a/engines/null.c
+++ b/engines/null.c
@@ -119,7 +119,7 @@ static struct ioengine_ops ioengine = {
 	.init		= fio_null_init,
 	.cleanup	= fio_null_cleanup,
 	.open_file	= fio_null_open,
-	.flags		= FIO_DISKLESSIO,
+	.flags		= FIO_DISKLESSIO | FIO_FAKEIO,
 };
 
 static void fio_init fio_null_register(void)
@@ -152,7 +152,7 @@ void get_ioengine(struct ioengine_ops **ioengine_ptr)
 	ioengine->init           = fio_null_init;
 	ioengine->cleanup        = fio_null_cleanup;
 	ioengine->open_file      = fio_null_open;
-	ioengine->flags	         = FIO_DISKLESSIO;
+	ioengine->flags	         = FIO_DISKLESSIO | FIO_FAKEIO;
 }
 }
 #endif /* FIO_EXTERNAL_ENGINE */
diff --git a/ioengine.h b/ioengine.h
index 29c8487a..ebe0ebe9 100644
--- a/ioengine.h
+++ b/ioengine.h
@@ -166,6 +166,7 @@ enum fio_ioengine_flags {
 	FIO_BARRIER	= 1 << 8,	/* engine supports barriers */
 	FIO_MEMALIGN	= 1 << 9,	/* engine wants aligned memory */
 	FIO_BIT_BASED	= 1 << 10,	/* engine uses a bit base (e.g. uses Kbit as opposed to KB) */
+	FIO_FAKEIO	= 1 << 11,	/* engine pretends to do IO */
 };
 
 /*
diff --git a/verify.c b/verify.c
index 217b6869..3d7c5de9 100644
--- a/verify.c
+++ b/verify.c
@@ -759,6 +759,13 @@ int verify_io_u(struct thread_data *td, struct io_u **io_u_ptr)
 
 	if (td->o.verify == VERIFY_NULL || io_u->ddir != DDIR_READ)
 		return 0;
+	/*
+	 * If the IO engine is faking IO (like null), then just pretend
+	 * we verified everything.
+	 */
+	if (td->io_ops->flags & FIO_FAKEIO)
+		return 0;
+
 	if (io_u->flags & IO_U_F_TRIMMED) {
 		ret = verify_trimmed_io_u(td, io_u);
 		goto done;
-- 
2.25.1