v4.19.13 snapshot.
diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h
new file mode 100644
index 0000000..25d985e
--- /dev/null
+++ b/fs/btrfs/extent_map.h
@@ -0,0 +1,99 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef BTRFS_EXTENT_MAP_H
+#define BTRFS_EXTENT_MAP_H
+
+#include <linux/rbtree.h>
+#include <linux/refcount.h>
+
+#define EXTENT_MAP_LAST_BYTE ((u64)-4)
+#define EXTENT_MAP_HOLE ((u64)-3)
+#define EXTENT_MAP_INLINE ((u64)-2)
+#define EXTENT_MAP_DELALLOC ((u64)-1)
+
+/* bits for the flags field */
+#define EXTENT_FLAG_PINNED 0 /* this entry not yet on disk, don't free it */
+#define EXTENT_FLAG_COMPRESSED 1
+#define EXTENT_FLAG_PREALLOC 3 /* pre-allocated extent */
+#define EXTENT_FLAG_LOGGING 4 /* Logging this extent */
+#define EXTENT_FLAG_FILLING 5 /* Filling in a preallocated extent */
+#define EXTENT_FLAG_FS_MAPPING 6 /* filesystem extent mapping type */
+
+struct extent_map {
+ struct rb_node rb_node;
+
+ /* all of these are in bytes */
+ u64 start;
+ u64 len;
+ u64 mod_start;
+ u64 mod_len;
+ u64 orig_start;
+ u64 orig_block_len;
+ u64 ram_bytes;
+ u64 block_start;
+ u64 block_len;
+ u64 generation;
+ unsigned long flags;
+ union {
+ struct block_device *bdev;
+
+ /*
+ * used for chunk mappings
+ * flags & EXTENT_FLAG_FS_MAPPING must be set
+ */
+ struct map_lookup *map_lookup;
+ };
+ refcount_t refs;
+ unsigned int compress_type;
+ struct list_head list;
+};
+
+struct extent_map_tree {
+ struct rb_root map;
+ struct list_head modified_extents;
+ rwlock_t lock;
+};
+
+static inline int extent_map_in_tree(const struct extent_map *em)
+{
+ return !RB_EMPTY_NODE(&em->rb_node);
+}
+
+static inline u64 extent_map_end(struct extent_map *em)
+{
+ if (em->start + em->len < em->start)
+ return (u64)-1;
+ return em->start + em->len;
+}
+
+static inline u64 extent_map_block_end(struct extent_map *em)
+{
+ if (em->block_start + em->block_len < em->block_start)
+ return (u64)-1;
+ return em->block_start + em->block_len;
+}
+
+void extent_map_tree_init(struct extent_map_tree *tree);
+struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
+ u64 start, u64 len);
+int add_extent_mapping(struct extent_map_tree *tree,
+ struct extent_map *em, int modified);
+int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em);
+void replace_extent_mapping(struct extent_map_tree *tree,
+ struct extent_map *cur,
+ struct extent_map *new,
+ int modified);
+
+struct extent_map *alloc_extent_map(void);
+void free_extent_map(struct extent_map *em);
+int __init extent_map_init(void);
+void __cold extent_map_exit(void);
+int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len, u64 gen);
+void clear_em_logging(struct extent_map_tree *tree, struct extent_map *em);
+struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
+ u64 start, u64 len);
+int btrfs_add_extent_mapping(struct btrfs_fs_info *fs_info,
+ struct extent_map_tree *em_tree,
+ struct extent_map **em_in, u64 start, u64 len);
+
+#endif