[RFC PATCH 2/9] dm: add methods to set and get reserved space

[Brian Foster <bfoster@xxxxxxxxxx>]

From: Mike Snitzer <snitzer@xxxxxxxxxx>

Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
 drivers/md/dm.c               | 75 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/device-mapper.h |  5 +++
 2 files changed, 80 insertions(+)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index be49057..4da5d3e 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -664,6 +664,79 @@ out:
 	return r;
 }
 
+/*
+ * FIXME: factor out common helper that can be used by
+ * multiple block_device_operations -> target methods
+ * (including dm_blk_ioctl above)
+ */
+
+static int dm_blk_reserve_space(struct block_device *bdev, sector_t nr_sects)
+{
+	struct mapped_device *md = bdev->bd_disk->private_data;
+	int srcu_idx;
+	struct dm_table *map;
+	struct dm_target *tgt;
+	int r = -EINVAL;
+
+	map = dm_get_live_table(md, &srcu_idx);
+
+	if (!map || !dm_table_get_size(map))
+		goto out;
+
+	/* We only support devices that have a single target */
+	if (dm_table_get_num_targets(map) != 1)
+		goto out;
+
+	tgt = dm_table_get_target(map, 0);
+	if (!tgt->type->reserve_space)
+		goto out;
+
+	if (dm_suspended_md(md)) {
+		r = -EAGAIN;
+		goto out;
+	}
+
+	r = tgt->type->reserve_space(tgt, nr_sects);
+out:
+	dm_put_live_table(md, srcu_idx);
+
+	return r;
+}
+
+static int dm_blk_get_reserved_space(struct block_device *bdev,
+				     sector_t *nr_sects)
+{
+	struct mapped_device *md = bdev->bd_disk->private_data;
+	int srcu_idx;
+	struct dm_table *map;
+	struct dm_target *tgt;
+	int r = -EINVAL;
+
+	map = dm_get_live_table(md, &srcu_idx);
+
+	if (!map || !dm_table_get_size(map))
+		goto out;
+
+	/* We only support devices that have a single target */
+	if (dm_table_get_num_targets(map) != 1)
+		goto out;
+
+	tgt = dm_table_get_target(map, 0);
+	if (!tgt->type->get_reserved_space)
+		goto out;
+
+	if (dm_suspended_md(md)) {
+		r = -EAGAIN;
+		goto out;
+	}
+
+	r = tgt->type->get_reserved_space(tgt, nr_sects);
+out:
+	dm_put_live_table(md, srcu_idx);
+
+	return r;
+}
+
 static struct dm_io *alloc_io(struct mapped_device *md)
 {
 	return mempool_alloc(md->io_pool, GFP_NOIO);
@@ -3723,6 +3796,8 @@ static const struct block_device_operations dm_blk_dops = {
 	.ioctl = dm_blk_ioctl,
 	.getgeo = dm_blk_getgeo,
 	.pr_ops = &dm_pr_ops,
+	.reserve_space = dm_blk_reserve_space,
+	.get_reserved_space = dm_blk_get_reserved_space,
 	.owner = THIS_MODULE
 };
 
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 0830c9e..540c772 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -116,6 +116,9 @@ typedef void (*dm_io_hints_fn) (struct dm_target *ti,
  */
 typedef int (*dm_busy_fn) (struct dm_target *ti);
 
+typedef int (*dm_reserve_space_fn) (struct dm_target *ti, sector_t nr_sects);
+typedef int (*dm_get_reserved_space_fn) (struct dm_target *ti, sector_t *nr_sects);
+
 void dm_error(const char *message);
 
 struct dm_dev {
@@ -162,6 +165,8 @@ struct target_type {
 	dm_busy_fn busy;
 	dm_iterate_devices_fn iterate_devices;
 	dm_io_hints_fn io_hints;
+	dm_reserve_space_fn reserve_space;
+	dm_get_reserved_space_fn get_reserved_space;
 
 	/* For internal device-mapper use. */
 	struct list_head list;
-- 
2.4.3

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