From 0b35a81ccda06c6711cdf3cbae1a0cff033ca25e Mon Sep 17 00:00:00 2001
From: Simon P. Graham <Simon.Graham@stratus.com>
Date: Mon, 14 Apr 2008 10:35:33 -0400
Subject: [PATCH] Add support for standard disk stats to DRBD devices

---
 drbd/drbd_int.h |    1 +
 drbd/drbd_req.c |   38 ++++++++++++++++++++++++++++++++++++++
 drbd/drbd_req.h |    1 +
 3 files changed, 40 insertions(+), 0 deletions(-)

diff --git a/drbd/drbd_int.h b/drbd/drbd_int.h
index 8f693f3..05edc55 100644
--- a/drbd/drbd_int.h
+++ b/drbd/drbd_int.h
@@ -629,6 +629,7 @@ struct drbd_request {
 	struct bio *master_bio;       /* master bio pointer */
 	unsigned long rq_state; /* see comments above _req_mod() */
 	int seq_num;
+	unsigned long start_time;
 };
 
 struct drbd_barrier {
diff --git a/drbd/drbd_req.c b/drbd/drbd_req.c
index f06a0e4..d75b674 100644
--- a/drbd/drbd_req.c
+++ b/drbd/drbd_req.c
@@ -105,6 +105,37 @@ void _print_req_mod(drbd_request_t *req,drbd_req_event_t what)
 #define print_req_mod(T,W)
 #endif
 
+/* Update disk stats at start of I/O request */
+static inline void _drbd_start_io_acct(drbd_dev *mdev, drbd_request_t *req, struct bio *bio)
+{
+	int rw = bio_data_dir(bio);
+
+	MUST_HOLD(&mdev->req_lock)
+
+	disk_stat_inc(mdev->vdisk, ios[rw]);
+	disk_stat_add(mdev->vdisk, sectors[rw], bio_sectors(bio));
+	preempt_disable();
+	disk_round_stats(mdev->vdisk);
+	preempt_enable();
+	mdev->vdisk->in_flight++;
+}
+
+/* Update disk stats when completing request upwards */
+static inline void _drbd_end_io_acct(drbd_dev *mdev, drbd_request_t *req)
+{
+	int rw = bio_data_dir(req->master_bio);
+	unsigned long duration = jiffies - req->start_time;
+
+	MUST_HOLD(&mdev->req_lock)
+
+	preempt_disable();
+	disk_round_stats(mdev->vdisk);
+	preempt_enable();
+	mdev->vdisk->in_flight--;
+
+	disk_stat_add(mdev->vdisk, ticks[rw], duration);
+}
+
 static void _req_is_done(drbd_dev *mdev, drbd_request_t *req, const int rw)
 {
 	const unsigned long s = req->rq_state;
@@ -335,6 +366,9 @@ void _req_may_be_done(drbd_request_t *req, int error)
 		 * then again, if it is a READ, it is not in the TL at all.
 		 * is it still leagal to complete a READ during freeze? */
 
+		/* Update disk stats */
+		_drbd_end_io_acct(mdev, req);
+
 		_complete_master_bio(mdev,req,
 			  ok ? 0 : ( error ? error : -EIO ) );
 	} else {
@@ -956,6 +990,9 @@ drbd_make_request_common(drbd_dev *mdev, struct bio *bio)
 	}
 
 
+	/* Update disk stats */
+	_drbd_start_io_acct(mdev, req, bio);
+
 	/* _maybe_start_new_epoch(mdev);
 	 * If we need to generate a write barrier packet, we have to add the
 	 * new epoch (barrier) object, and queue the barrier packet for sending,
@@ -1012,6 +1049,7 @@ drbd_make_request_common(drbd_dev *mdev, struct bio *bio)
 			local = 0;
 		}
 		if (remote) dec_ap_pending(mdev);
+		_drbd_end_io_acct(mdev, req);
 		/* THINK: do we want to fail it (-EIO), or pretend success? */
 		bio_endio(req->master_bio, 0);
 		req->master_bio = NULL;
diff --git a/drbd/drbd_req.h b/drbd/drbd_req.h
index 1d981b2..74d8dc1 100644
--- a/drbd/drbd_req.h
+++ b/drbd/drbd_req.h
@@ -284,6 +284,7 @@ static inline drbd_request_t* drbd_req_new(drbd_dev *mdev, struct bio *bio_src)
 		req->epoch       = 0;
 		req->sector      = bio->bi_sector;
 		req->size        = bio->bi_size;
+		req->start_time  = jiffies;
 		INIT_HLIST_NODE(&req->colision);
 		INIT_LIST_HEAD(&req->tl_requests);
 
-- 
1.5.4-rc1.GIT