[PATCH 1/7] btrfs: add flags to give an hint to the chunk allocator

[Goffredo Baroncelli <kreijack@tiscali.it>]

From: Goffredo Baroncelli <kreijack@inwind.it>

Add the following flags to give an hint about which chunk should be
allocated in which disk:

- BTRFS_DEV_ALLOCATION_HINT_DATA_PREFERRED
  preferred for data chunk, but metadata chunk allowed
- BTRFS_DEV_ALLOCATION_HINT_METADATA_PREFERRED
  preferred for metadata chunk, but data chunk allowed
- BTRFS_DEV_ALLOCATION_HINT_METADATA_ONLY
  only metadata chunk allowed
- BTRFS_DEV_ALLOCATION_HINT_DATA_ONLY
  only data chunk allowed

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
---
 include/uapi/linux/btrfs_tree.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h
index 5416f1f1a77a..02955d5fcd21 100644
--- a/include/uapi/linux/btrfs_tree.h
+++ b/include/uapi/linux/btrfs_tree.h
@@ -386,6 +386,22 @@ struct btrfs_key {
 	__u64 offset;
 } __attribute__ ((__packed__));
 
+/* dev_item.type */
+
+/* btrfs chunk allocation hint */
+#define BTRFS_DEV_ALLOCATION_HINT_BIT_COUNT	2
+/* btrfs chunk allocation hint mask */
+#define BTRFS_DEV_ALLOCATION_HINT_MASK	\
+	((1 << BTRFS_DEV_ALLOCATION_HINT_BIT_COUNT) - 1)
+/* preferred data chunk, but metadata chunk allowed */
+#define BTRFS_DEV_ALLOCATION_HINT_DATA_PREFERRED	(0ULL)
+/* preferred metadata chunk, but data chunk allowed */
+#define BTRFS_DEV_ALLOCATION_HINT_METADATA_PREFERRED	(1ULL)
+/* only metadata chunk are allowed */
+#define BTRFS_DEV_ALLOCATION_HINT_METADATA_ONLY		(2ULL)
+/* only data chunk allowed */
+#define BTRFS_DEV_ALLOCATION_HINT_DATA_ONLY		(3ULL)
+
 struct btrfs_dev_item {
 	/* the internal btrfs device id */
 	__le64 devid;
-- 
2.34.1