[PATCH 12/21] init: fixup verify_offset option

Verify offset should swap verification header within the verify interval.
If this is not the case return error. Update the doc. accordingly.

Signed-off-by: Ankit Kumar <[email protected]>
---
 HOWTO.rst |  3 ++-
 fio.1     |  3 ++-
 init.c    | 11 +++++++++++
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/HOWTO.rst b/HOWTO.rst
index ca0044ce..4293c03c 100644
--- a/HOWTO.rst
+++ b/HOWTO.rst
@@ -3929,7 +3929,8 @@ Verification
 .. option:: verify_offset=int
 
 	Swap the verification header with data somewhere else in the block before
-	writing. It is swapped back before verifying.
+	writing. It is swapped back before verifying. This should be within the
+	range of :option:`verify_interval`.
 
 .. option:: verify_interval=int
 
diff --git a/fio.1 b/fio.1
index fd580258..a0f204c0 100644
--- a/fio.1
+++ b/fio.1
@@ -3654,7 +3654,8 @@ same offset with multiple outstanding I/Os.
 .TP
 .BI verify_offset \fR=\fPint
 Swap the verification header with data somewhere else in the block before
-writing. It is swapped back before verifying.
+writing. It is swapped back before verifying. This should be within the range
+of \fBverify_interval\fR.
 .TP
 .BI verify_interval \fR=\fPint
 Write the verification header at a finer granularity than the
diff --git a/init.c b/init.c
index 00a3a8c7..bf257ea1 100644
--- a/init.c
+++ b/init.c
@@ -873,6 +873,17 @@ static int fixup_options(struct thread_data *td)
 				o->verify_write_sequence = 0;
 		}
 
+		/*
+		 * Verify header should not be offset beyond the verify
+		 * interval.
+		 */
+		if (o->verify_offset + sizeof(struct verify_header) >
+		    o->verify_interval) {
+			log_err("fio: cannot offset verify header beyond the "
+				"verify interval.\n");
+			ret |= 1;
+		}
+
 		/*
 		 * Disable rand_seed check when we have verify_backlog,
 		 * zone reset frequency for zonemode=zbd, or norandommap.
-- 
2.25.1