[RFC v2 PATCH 04/10] dm: add methods to set and get reserved space

[Brian Foster <bfoster@xxxxxxxxxx>]

From: Mike Snitzer <snitzer@xxxxxxxxxx>

[BF: Condensed to single function.]

Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
 drivers/md/dm.c               | 41 +++++++++++++++++++++++++++++++++++++++++
 include/linux/device-mapper.h |  5 +++++
 2 files changed, 46 insertions(+)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index be49057..8f95e78 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -664,6 +664,46 @@ 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, int mode,
+                               sector_t offset, sector_t len, sector_t *res)
+{
+       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, mode, offset, len, res);
+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 +3763,7 @@ 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,
        .owner = THIS_MODULE
 };
 
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 0830c9e..b4825db 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -116,6 +116,10 @@ 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, int mode,
+                                   sector_t offset, sector_t len,
+                                   sector_t *res);
+
 void dm_error(const char *message);
 
 struct dm_dev {
@@ -162,6 +166,7 @@ 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;
 
        /* For internal device-mapper use. */
        struct list_head list;
-- 
2.4.11