linux-kernel - [PATCH] dm: pass up rotational flag

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Message-Id: <1306356648-30730-1-git-send-email-msb@chromium.org>
Date:	Wed, 25 May 2011 13:50:48 -0700
From:	Mandeep Singh Baines <msb@...omium.org>
To:	linux-kernel@...r.kernel.org, jrbarnette@...omium.org
Cc:	Mandeep Singh Baines <msb@...omium.org>,
	Neil Brown <neilb@...e.de>, Mike Snitzer <snitzer@...hat.com>,
	Jens Axboe <jaxboe@...ionio.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Alasdair G Kergon <agk@...hat.com>, dm-devel@...hat.com
Subject: [PATCH] dm: pass up rotational flag

Allow the NONROT flag to be passed through to linear mappings if all
underlying device are non-rotational. Tools like ureadahead will
schedule IOs differently based on the rotational flag.

With this patch, I see boot time go from 7.75 s to 7.46 s on my device.

Suggested-by: J. Richard Barnette <jrbarnette@...omium.org>
Signed-off-by: Mandeep Singh Baines <msb@...omium.org>
Cc: Neil Brown <neilb@...e.de>
Cc: Mike Snitzer <snitzer@...hat.com>
Cc: Jens Axboe <jaxboe@...ionio.com>
Cc: Martin K. Petersen <martin.petersen@...cle.com>
Cc: Alasdair G Kergon <agk@...hat.com>
Cc: dm-devel@...hat.com
---
 drivers/md/dm-table.c |   28 ++++++++++++++++++++++++++++
 1 files changed, 28 insertions(+), 0 deletions(-)

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index cb8380c..40c6071 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1177,6 +1177,30 @@ static void dm_table_set_integrity(struct dm_table *t)
 			       blk_get_integrity(template_disk));
 }
 
+static int device_nonrot(struct dm_target *ti, struct dm_dev *dev,
+			       sector_t start, sector_t len, void *data)
+{
+	struct request_queue *q = bdev_get_queue(dev->bdev);
+
+	return q && blk_queue_nonrot(q);
+}
+
+static bool dm_table_all_nonrot(struct dm_table *t)
+{
+	unsigned i = 0;
+
+	/* Ensure that all underlying device are non rotational. */
+	while (i < dm_table_get_num_targets(t)) {
+		struct dm_target *ti = dm_table_get_target(t, i++);
+
+		if (!ti->type->iterate_devices ||
+		    !ti->type->iterate_devices(ti, device_nonrot, NULL))
+			return false;
+	}
+
+	return true;
+}
+
 void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 			       struct queue_limits *limits)
 {
@@ -1189,6 +1213,10 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 		queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
 	else
 		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
+	if (!dm_table_all_nonrot(t))
+		queue_flag_clear_unlocked(QUEUE_FLAG_NONROT, q);
+	else
+		queue_flag_set_unlocked(QUEUE_FLAG_NONROT, q);
 
 	dm_table_set_integrity(t);
 
-- 
1.7.3.1

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