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, 3 insertions, 3 deletions

diff --git a/fs/bcachefs/dirent.h b/fs/bcachefs/dirent.h
index 34769371dd13..e1d8ce377d43 100644
--- a/fs/bcachefs/dirent.h
+++ b/fs/bcachefs/dirent.h
@@ -31,7 +31,7 @@ static inline unsigned dirent_val_u64s(unsigned len)
 
 int bch2_dirent_create(struct btree_trans *, u64,
 		       const struct bch_hash_info *, u8,
-		       const struct qstr *, u64, int);
+		       const struct qstr *, u64, u64 *, int);
 
 int bch2_dirent_delete_at(struct btree_trans *,
 			  const struct bch_hash_info *,
@@ -46,8 +46,8 @@ enum bch_rename_mode {
 int bch2_dirent_rename(struct btree_trans *,
 		       u64, struct bch_hash_info *,
 		       u64, struct bch_hash_info *,
-		       const struct qstr *, u64 *,
-		       const struct qstr *, u64 *,
+		       const struct qstr *, u64 *, u64 *,
+		       const struct qstr *, u64 *, u64 *,
 		       enum bch_rename_mode);
 
 struct btree_iter *