[PATCH 3/3] raid0: conditional mddev->queue access to suit dm-raid

[heinzm@redhat.com]

From: Heinz Mauelshagen <heinzm@redhat.com>

This patch is a prerequisite for dm-raid "raid0" support to allow
dm-raid to access the MD RAID0 personality doing unconditional
accesses to mddev->queue, which is NULL in case of dm-raid stacked
on top of MD.

This patch is here for completeness; it has been send to Neil Brown
and linux-raid, Neil said he applied it on Feb 23rd but it did not
show up in upstream as yet.


Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Tested-by: Heinz Mauelshagen <heinzm@redhat.com>

---
 drivers/md/raid0.c | 48 +++++++++++++++++++++++++++---------------------
 1 file changed, 27 insertions(+), 21 deletions(-)

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 3ed9f42..e074813 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -271,14 +271,16 @@ static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf)
 		goto abort;
 	}
 
-	blk_queue_io_min(mddev->queue, mddev->chunk_sectors << 9);
-	blk_queue_io_opt(mddev->queue,
-			 (mddev->chunk_sectors << 9) * mddev->raid_disks);
-
-	if (!discard_supported)
-		queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
-	else
-		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+	if (mddev->queue) {
+		blk_queue_io_min(mddev->queue, mddev->chunk_sectors << 9);
+		blk_queue_io_opt(mddev->queue,
+				 (mddev->chunk_sectors << 9) * mddev->raid_disks);
+
+		if (!discard_supported)
+			queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+		else
+			queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+	}
 
 	pr_debug("md/raid0:%s: done.\n", mdname(mddev));
 	*private_conf = conf;
@@ -429,9 +431,12 @@ static int raid0_run(struct mddev *mddev)
 	}
 	if (md_check_no_bitmap(mddev))
 		return -EINVAL;
-	blk_queue_max_hw_sectors(mddev->queue, mddev->chunk_sectors);
-	blk_queue_max_write_same_sectors(mddev->queue, mddev->chunk_sectors);
-	blk_queue_max_discard_sectors(mddev->queue, mddev->chunk_sectors);
+
+	if (mddev->queue) {
+		blk_queue_max_hw_sectors(mddev->queue, mddev->chunk_sectors);
+		blk_queue_max_write_same_sectors(mddev->queue, mddev->chunk_sectors);
+		blk_queue_max_discard_sectors(mddev->queue, mddev->chunk_sectors);
+	}
 
 	/* if private is not null, we are here after takeover */
 	if (mddev->private == NULL) {
@@ -448,16 +453,17 @@ static int raid0_run(struct mddev *mddev)
 	printk(KERN_INFO "md/raid0:%s: md_size is %llu sectors.\n",
 	       mdname(mddev),
 	       (unsigned long long)mddev->array_sectors);
-	/* calculate the max read-ahead size.
-	 * For read-ahead of large files to be effective, we need to
-	 * readahead at least twice a whole stripe. i.e. number of devices
-	 * multiplied by chunk size times 2.
-	 * If an individual device has an ra_pages greater than the
-	 * chunk size, then we will not drive that device as hard as it
-	 * wants.  We consider this a configuration error: a larger
-	 * chunksize should be used in that case.
-	 */
-	{
+
+	if (mddev->queue) {
+		/* calculate the max read-ahead size.
+		 * For read-ahead of large files to be effective, we need to
+		 * readahead at least twice a whole stripe. i.e. number of devices
+		 * multiplied by chunk size times 2.
+		 * If an individual device has an ra_pages greater than the
+		 * chunk size, then we will not drive that device as hard as it
+		 * wants.  We consider this a configuration error: a larger
+		 * chunksize should be used in that case.
+		 */
 		int stripe = mddev->raid_disks *
 			(mddev->chunk_sectors << 9) / PAGE_SIZE;
 		if (mddev->queue->backing_dev_info.ra_pages < 2* stripe)
-- 
2.1.0