[dm-devel] [PATCH v2 2/4] dm: Start pr_reserve from the same starting path

[Mike Christie]

When an app does a pr_reserve it will go to whatever path we happen to
be using at the time. This can result in errors where the app does a
second pr_reserve call and expects success but gets a failure becuase
the reserve is not done on the holder's path. This patch has us always
start trying to do reserves from the first path in the first group.

Windows failover clustering will produce the type of pattern above. With
this patch, we will now pass its validation test for this case.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
---
 drivers/md/dm.c | 46 ++++++++++++++++++++++++++++++++--------------
 1 file changed, 32 insertions(+), 14 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 67b46ae896b1..cdd1656b99d6 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -3048,6 +3048,7 @@ struct dm_pr {
 	u32	flags;
 	bool	fail_early;
 	int	ret;
+	enum pr_type type;
 };
 
 static int dm_call_pr(struct block_device *bdev, iterate_devices_callout_fn fn,
@@ -3139,25 +3140,42 @@ static int dm_pr_register(struct block_device *bdev, u64 old_key, u64 new_key,
 	return ret;
 }
 
+
+static int __dm_pr_reserve(struct dm_target *ti, struct dm_dev *dev,
+			   sector_t start, sector_t len, void *data)
+{
+	struct dm_pr *pr = data;
+	const struct pr_ops *ops = dev->bdev->bd_disk->fops->pr_ops;
+
+	if (!ops || !ops->pr_reserve) {
+		pr->ret = -EOPNOTSUPP;
+		return -1;
+	}
+
+	pr->ret = ops->pr_reserve(dev->bdev, pr->old_key, pr->type, pr->flags);
+	if (!pr->ret)
+		return -1;
+
+	return 0;
+}
+
 static int dm_pr_reserve(struct block_device *bdev, u64 key, enum pr_type type,
 			 u32 flags)
 {
-	struct mapped_device *md = bdev->bd_disk->private_data;
-	const struct pr_ops *ops;
-	int r, srcu_idx;
+	struct dm_pr pr = {
+		.old_key	= key,
+		.flags		= flags,
+		.type		= type,
+		.fail_early	= false,
+		.ret		= 0,
+	};
+	int ret;
 
-	r = dm_prepare_ioctl(md, &srcu_idx, &bdev);
-	if (r < 0)
-		goto out;
+	ret = dm_call_pr(bdev, __dm_pr_reserve, &pr);
+	if (ret)
+		return ret;
 
-	ops = bdev->bd_disk->fops->pr_ops;
-	if (ops && ops->pr_reserve)
-		r = ops->pr_reserve(bdev, key, type, flags);
-	else
-		r = -EOPNOTSUPP;
-out:
-	dm_unprepare_ioctl(md, srcu_idx);
-	return r;
+	return pr.ret;
 }
 
 static int dm_pr_release(struct block_device *bdev, u64 key, enum pr_type type)
-- 
2.25.1