From: Horshack <horshack@live.com>
Date: Sat, 18 Feb 2023 20:22:54 +0000 (-0500)
Subject: Bad header rand_seed with time_based or loops with randrepeat=0 verify
X-Git-Tag: fio-3.34~16^2
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=50eaefa5cdaeb345df1f9902fe87d55aa48dc206;p=fio.git

Bad header rand_seed with time_based or loops with randrepeat=0 verify

Verify fails with "bad header rand_seed" when multiple iterations of
do_io() execute (time_based=1 or loops>0), with verify enabled
and randrepeat=0

The root cause is do_verify() resetting the verify seed back to the
job-init value, which works for verification of the first iteration of
do_io() but fails for subsequent iterations because the seed is left in
its post-do_io() state after the first do_verify(), which means
different rand values for the second iteration of do_io() yet the second
iteration of do_verify() will revert back again to the job-init seed
value.

The fix is to revert the verify seed for randrepeat=0 back to ts state
when do_io() last ran rather than to its job-init value. That will allow
do_verify() to use the correct seed for each iteration while still
retaining a per-iteration unique verify seed.

Link: https://github.com/axboe/fio/issues/1517#issuecomment-1430282533

Signed-off-by: Adam Horshack (horshack@live.com)
---

diff --git a/backend.c b/backend.c
index 0ccc7c2b..9ea688fb 100644
--- a/backend.c
+++ b/backend.c
@@ -637,15 +637,6 @@ static void do_verify(struct thread_data *td, uint64_t verify_bytes)
 	if (td->error)
 		return;
 
-	/*
-	 * verify_state needs to be reset before verification
-	 * proceeds so that expected random seeds match actual
-	 * random seeds in headers. The main loop will reset
-	 * all random number generators if randrepeat is set.
-	 */
-	if (!td->o.rand_repeatable)
-		td_fill_verify_state_seed(td);
-
 	td_set_runstate(td, TD_VERIFYING);
 
 	io_u = NULL;
@@ -1878,8 +1869,12 @@ static void *thread_main(void *data)
 		if (td->o.verify_only && td_write(td))
 			verify_bytes = do_dry_run(td);
 		else {
+			if (!td->o.rand_repeatable)
+				/* save verify rand state to replay hdr seeds later at verify */
+				frand_copy(&td->verify_state_last_do_io, &td->verify_state);
 			do_io(td, bytes_done);
-
+			if (!td->o.rand_repeatable)
+				frand_copy(&td->verify_state, &td->verify_state_last_do_io);
 			if (!ddir_rw_sum(bytes_done)) {
 				fio_mark_td_terminate(td);
 				verify_bytes = 0;
diff --git a/fio.h b/fio.h
index 8da77640..09c44149 100644
--- a/fio.h
+++ b/fio.h
@@ -258,6 +258,7 @@ struct thread_data {
 
 	struct frand_state bsrange_state[DDIR_RWDIR_CNT];
 	struct frand_state verify_state;
+	struct frand_state verify_state_last_do_io;
 	struct frand_state trim_state;
 	struct frand_state delay_state;