bcachefs: make directory i_size meaningful

The isize of directory is 0 in bcachefs if the directory is empty.
With more child dirents created, its size ought to change. Many
other filesystems changed as that (ie. xfs and btrfs). And many of
them changed as the size of child dirent name. Although the directory
size may not seem to convey much, we can still give it some meaning.

The formula of dentry size as follow:
    occupied_size = 40 + ALIGN(9 + namelen, 8)

Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/bcachefs/dirent.h b/fs/bcachefs/dirent.h
index 362b3b2f2f2e..a633f83c1ac7 100644
--- a/fs/bcachefs/dirent.h
+++ b/fs/bcachefs/dirent.h
@@ -31,6 +31,11 @@ static inline unsigned dirent_val_u64s(unsigned len)
 			    sizeof(u64));
 }
 
+static inline unsigned int dirent_occupied_size(const struct qstr *name)
+{
+	return (BKEY_U64s + dirent_val_u64s(name->len)) * sizeof(u64);
+}
+
 int bch2_dirent_read_target(struct btree_trans *, subvol_inum,
 			    struct bkey_s_c_dirent, subvol_inum *);