RE: [PATCH V2] Adds verify_only option.

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Hi Juan,

Two questions:
1. How fio knows where is the last block (where to stop verification run)? Please let me know if I understand it correctly: because lfsr runs without duplicated blocks then number of iterations is device_size/block_size.
2. You wrote: "The verify_only option performs only verification (reads performed in do_verify()) and no read or write workload". But for verification, even if you made dry run till the end, you need to read. I don't follow.

Regards
Konstantin

-----Original Message-----
From: fio-owner@xxxxxxxxxxxxxxx [mailto:fio-owner@xxxxxxxxxxxxxxx] On Behalf Of Juan Casse
Sent: Friday, September 13, 2013 11:07 PM
To: Jens Axboe
Cc: Grant Grundler; fio@xxxxxxxxxxxxxxx; Juan Casse
Subject: [PATCH V2] Adds verify_only option.

The verify_only option performs only verification (reads performed in do_verify()) and no read or write workload. The goal is to verify previously written meta data quickly and be able to detect stale data.
Without this option, fio does not detect stale data from previous fio runs---only data corruption of "misplaced" data.

This option replays the specified write workload sequence in order to compute the "generation number" (using numberio field) for each block header that was written in a previous fio run. The numberio field is used to detect stale data. do_verify() checks numberio only in the last iteration, after the correct numberio for each block has been computed.
---
 HOWTO            |  8 ++++++-
 README           |  2 ++
 backend.c        | 64 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 init.c           | 17 +++++++++++++++
 options.c        |  9 ++++++++
 thread_options.h |  2 ++
 verify.c         |  8 +++++--
 7 files changed, 106 insertions(+), 4 deletions(-)

diff --git a/HOWTO b/HOWTO
index 005dac2..ac35342 100644
--- a/HOWTO
+++ b/HOWTO
@@ -1039,6 +1039,10 @@ loops=int	Run the specified number of iterations of this job. Used
 		to repeat the same workload a given number of times. Defaults
 		to 1.
 
+verify_only	Check for stale data written to storage in a previous fio run.
+		The workload used must match the one used in the previous run.
+		This works for workloads that write data.
+
 do_verify=bool	Run the verify phase after a write phase. Only makes sense if
 		verify is set. Defaults to 1.
 
@@ -1077,7 +1081,9 @@ verify=str	If writing to a file, fio can verify the file contents
 
 			meta	Write extra information about each io
 				(timestamp, block number etc.). The block
-				number is verified. See also verify_pattern.
+				number is verified. The io sequence number is
+				verified for workloads that write data.
+				See also verify_pattern.
 
 			null	Only pretend to verify. Useful for testing
 				internals with ioengine=null, not for much diff --git a/README b/README index 15a0731..7942069 100644
--- a/README
+++ b/README
@@ -141,6 +141,8 @@ $ fio
 	--latency-log		Generate per-job latency logs
 	--bandwidth-log		Generate per-job bandwidth logs
 	--minimal		Minimal (terse) output
+	--verifyonly		Skip workload io and only verify data
+				(includes stale data check)
 	--output-format=type	Output format (terse,json,normal)
 	--terse-version=type	Terse version output format (default 3, or 2 or 4).
 	--version		Print version info and exit
diff --git a/backend.c b/backend.c
index b9c1c12..39c2ba7 100644
--- a/backend.c
+++ b/backend.c
@@ -1104,6 +1104,65 @@ static int exec_string(struct thread_options *o, const char *string, const char  }
 
 /*
+ * Dry run to compute correct state of numberio for verification.
+ */
+static uint64_t do_dry_run(struct thread_data *td) {
+	uint64_t bytes_done[DDIR_RWDIR_CNT] = { 0, 0, 0 };
+	unsigned int i;
+	int ret = 0;
+
+	if (in_ramp_time(td))
+		td_set_runstate(td, TD_RAMP);
+	else
+		td_set_runstate(td, TD_RUNNING);
+
+	while ((td->o.read_iolog_file && !flist_empty(&td->io_log_list)) ||
+		(!flist_empty(&td->trim_list)) || !io_bytes_exceeded(td) ||
+		td->o.time_based) {
+		struct io_u *io_u;
+		enum fio_ddir ddir;
+
+		if (td->terminate || td->done)
+			break;
+
+		if (flow_threshold_exceeded(td))
+			continue;
+
+		io_u = get_io_u(td);
+		if (!io_u)
+			break;
+
+		ddir = io_u->ddir;
+
+		/*
+		 * Substitute for td_io_queue(); avoids any io
+		 */
+		io_u->flags |= IO_U_F_FLIGHT;
+		io_u->error = 0;
+		io_u->resid = 0;
+		if (ddir_rw(acct_ddir(io_u)))
+			td->io_issues[acct_ddir(io_u)]++;
+		if (ddir_rw(io_u->ddir)) {
+			io_u_mark_depth(td, 1);
+			td->ts.total_io_u[io_u->ddir]++;
+		}
+
+		ret = io_u_sync_complete(td, io_u, bytes_done);
+
+		if (!ddir_rw_sum(bytes_done) && !(td->io_ops->flags & FIO_NOIO))
+			continue;
+	}
+
+	if (td->o.fill_device && td->error == ENOSPC) {
+		td->error = 0;
+		td->terminate = 1;
+	}
+
+	return bytes_done[DDIR_WRITE] + bytes_done[DDIR_TRIM]; }
+
+/*
  * Entry point for the thread based jobs. The process based jobs end up
  * here as well, after a little setup.
  */
@@ -1311,7 +1370,10 @@ static void *thread_main(void *data)
 
 		prune_io_piece_log(td);
 
-		verify_bytes = do_io(td);
+		if (td->o.verify_only && (td_write(td) || td_rw(td)))
+			verify_bytes = do_dry_run(td);
+		else
+			verify_bytes = do_io(td);
 
 		clear_state = 1;
 
diff --git a/init.c b/init.c
index 1afc341..34d1f14 100644
--- a/init.c
+++ b/init.c
@@ -60,6 +60,8 @@ int write_bw_log = 0;
 int read_only = 0;
 int status_interval = 0;
 
+int verify_only = 0;
+
 static int write_lat_log;
 
 static int prev_group_jobs;
@@ -139,6 +141,11 @@ static struct option l_opts[FIO_NR_OPTIONS] = {
 		.val		= 'r' | FIO_CLIENT_FLAG,
 	},
 	{
+		.name		= (char *) "verifyonly",
+		.has_arg	= no_argument,
+		.val		= 'y' | FIO_CLIENT_FLAG,
+	},
+	{
 		.name		= (char *) "eta",
 		.has_arg	= required_argument,
 		.val		= 'e' | FIO_CLIENT_FLAG,
@@ -928,6 +935,13 @@ static int add_job(struct thread_data *td, const char *jobname, int job_add_num,
 	int numjobs, file_alloced;
 	struct thread_options *o = &td->o;
 
+	/* 
+	 * Ensure job option verify_only is set when provided as a
+	 * command-line argument.
+	 */
+	if (verify_only)
+		o->verify_only = 1;
+
 	/*
 	 * the def_thread is just for options, it's not a real job
 	 */
@@ -1661,6 +1675,9 @@ int parse_cmd_line(int argc, char *argv[], int client_type)
 		case 'r':
 			read_only = 1;
 			break;
+		case 'y':
+			verify_only = 1;
+			break;
 		case 'v':
 			if (!cur_client) {
 				log_info("%s\n", fio_version_string); diff --git a/options.c b/options.c index caf89d3..e6b9ec9 100644
--- a/options.c
+++ b/options.c
@@ -1935,6 +1935,15 @@ struct fio_option fio_options[FIO_MAX_OPTS] = {
 		.group	= FIO_OPT_G_RUNTIME,
 	},
 	{
+		.name	= "verify_only",
+		.lname	= "Verify only",
+		.type	= FIO_OPT_STR_SET,
+		.off1	= td_var_offset(verify_only),
+		.help	= "Verifies previously written data is still valid",
+		.category = FIO_OPT_C_GENERAL,
+		.group	= FIO_OPT_G_RUNTIME,
+	},
+	{
 		.name	= "ramp_time",
 		.lname	= "Ramp time",
 		.type	= FIO_OPT_STR_VAL_TIME,
diff --git a/thread_options.h b/thread_options.h index 3f345c5..c9660b4 100644
--- a/thread_options.h
+++ b/thread_options.h
@@ -107,6 +107,8 @@ struct thread_options {
 	unsigned int fsync_on_close;
 	unsigned int bs_is_seq_rand;
 
+	unsigned int verify_only;
+
 	unsigned int random_distribution;
 
 	fio_fp64_t zipf_theta;
diff --git a/verify.c b/verify.c
index 63def12..9343ab9 100644
--- a/verify.c
+++ b/verify.c
@@ -373,10 +373,14 @@ static int verify_io_u_meta(struct verify_header *hdr, struct vcont *vc)
 	 * For read-only workloads, the program cannot be certain of the
 	 * last numberio written to a block. Checking of numberio will be done
 	 * only for workloads that write data.
+	 * For verify_only, numberio will be checked in the last iteration when
+	 * the correct state of numberio, that would have been written to each
+	 * block in a previous run of fio, has been reached.
 	 */
 	if (td_write(td) || td_rw(td))
-		if (vh->numberio != io_u->numberio)
-			ret = EILSEQ;
+		if (!td->o.verify_only || td->o.loops == 0)
+			if (vh->numberio != io_u->numberio)
+				ret = EILSEQ;
 
 	if (!ret)
 		return 0;
--
1.7.12.4

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