btrfs: move ulists to data extent sharedness check context

When calling btrfs_is_data_extent_shared() we pass two ulists that were
allocated by the caller. This is because the single caller, fiemap, calls
btrfs_is_data_extent_shared() multiple times and the ulists can be reused,
instead of allocating new ones before each call and freeing them after
each call.

Now that we have a context structure/object that we pass to
btrfs_is_data_extent_shared(), we can move those ulists to it, and hide
their allocation and the context's allocation in a helper function, as
well as the freeing of the ulists and the context object. This allows to
reduce the number of parameters passed to btrfs_is_data_extent_shared(),
the need to pass the ulists from extent_fiemap() to fiemap_process_hole()
and having the caller deal with allocating and releasing the ulists.

Also rename one of the ulists from 'tmp' / 'tmp_ulist' to 'refs', since
that's a much better name as it reflects what the list is used for (and
matching the argument name for find_parent_nodes()).

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/btrfs/backref.h b/fs/btrfs/backref.h
index e3a2b45a76e3..8da0ba6b94a4 100644
--- a/fs/btrfs/backref.h
+++ b/fs/btrfs/backref.h
@@ -24,6 +24,9 @@ struct btrfs_backref_shared_cache_entry {
 };
 
 struct btrfs_backref_share_check_ctx {
+	/* Ulists used during backref walking. */
+	struct ulist refs;
+	struct ulist roots;
 	/*
 	 * A path from a root to a leaf that has a file extent item pointing to
 	 * a given data extent should never exceed the maximum b+tree height.
@@ -35,6 +38,9 @@ struct btrfs_backref_share_check_ctx {
 typedef int (iterate_extent_inodes_t)(u64 inum, u64 offset, u64 root,
 		void *ctx);
 
+struct btrfs_backref_share_check_ctx *btrfs_alloc_backref_share_check_ctx(void);
+void btrfs_free_backref_share_ctx(struct btrfs_backref_share_check_ctx *ctx);
+
 int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
 			struct btrfs_path *path, struct btrfs_key *found_key,
 			u64 *flags);
@@ -79,7 +85,6 @@ int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
 			  u64 *found_off);
 int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
 				u64 extent_gen,
-				struct ulist *roots, struct ulist *tmp,
 				struct btrfs_backref_share_check_ctx *ctx);
 
 int __init btrfs_prelim_ref_init(void);