bcachefs: Inode backpointers

This patch adds two new inode fields, bi_dir and bi_dir_offset, that
point back to the inode's dirent.

Since we're only adding fields for a single backpointer, files that have
been hardlinked won't necessarily have valid backpointers: we also add a
new inode flag, BCH_INODE_BACKPTR_UNTRUSTED, that's set if an inode has
ever had multiple links to it. That's ok, because we only really need
this functionality for directories, which can never have multiple
hardlinks - when we add subvolumes, we'll need a way to enemurate and
print subvolumes, and this will let us reconstruct a path to a subvolume
root given a subvolume root inode.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/bcachefs/inode.h b/fs/bcachefs/inode.h
index 1caf036ae928..6bad6dfb7989 100644
--- a/fs/bcachefs/inode.h
+++ b/fs/bcachefs/inode.h
@@ -69,7 +69,8 @@ void bch2_inode_init(struct bch_fs *, struct bch_inode_unpacked *,
 		     uid_t, gid_t, umode_t, dev_t,
 		     struct bch_inode_unpacked *);
 
-int bch2_inode_create(struct btree_trans *, struct bch_inode_unpacked *);
+struct btree_iter *bch2_inode_create(struct btree_trans *,
+				     struct bch_inode_unpacked *);
 
 int bch2_inode_rm(struct bch_fs *, u64, bool);