bcachefs: bch2_inum_to_path()

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

5 files changed, 125 insertions, 0 deletions

diff --git a/fs/bcachefs/errcode.h b/fs/bcachefs/errcode.h
index af25d8ec60f2..dcf70cfaeaa4 100644
--- a/fs/bcachefs/errcode.h
+++ b/fs/bcachefs/errcode.h
@@ -114,6 +114,7 @@
 	x(ENOENT,			ENOENT_dirent_doesnt_match_inode)	\
 	x(ENOENT,			ENOENT_dev_not_found)			\
 	x(ENOENT,			ENOENT_dev_idx_not_found)		\
+	x(ENOENT,			ENOENT_no_backpointer)			\
 	x(ENOTEMPTY,			ENOTEMPTY_dir_not_empty)		\
 	x(ENOTEMPTY,			ENOTEMPTY_subvol_not_empty)		\
 	x(0,				open_buckets_empty)			\
diff --git a/fs/bcachefs/fs-common.c b/fs/bcachefs/fs-common.c
index 624e6f963240..7d1180036954 100644
--- a/fs/bcachefs/fs-common.c
+++ b/fs/bcachefs/fs-common.c
@@ -547,3 +547,88 @@ err:
 	bch2_trans_iter_exit(trans, &src_dir_iter);
 	return ret;
 }
+
+static void memreverse(char *dst, const char *src, size_t len)
+{
+	src += len;
+	while (len--)
+		*dst++ = *--src;
+}
+
+static void memreverse_inplace(char *p1, size_t len)
+{
+	char *p2  = p1 + len;
+	while (p2 > p1)
+		swap(*p1++, *--p2);
+}
+
+int bch2_inum_to_path_trans(struct btree_trans *trans, subvol_inum inum, darray_char *path)
+{
+	struct btree_iter iter = {};
+	int ret;
+
+	darray_init(path);
+
+	while (true) {
+		ret = darray_push(path, '/');
+		if (ret)
+			goto err;
+
+		if (inum.subvol == BCACHEFS_ROOT_SUBVOL &&
+		    inum.inum	== BCACHEFS_ROOT_INO)
+			break;
+
+		struct bch_inode_unpacked inode_u;
+		ret = bch2_inode_find_by_inum_trans(trans, inum, &inode_u);
+		if (ret)
+			goto err;
+
+		if (!inode_u.bi_dir) {
+			ret = -BCH_ERR_ENOENT_no_backpointer;
+			goto err;
+		}
+
+		u32 subvol = inode_u.bi_parent_subvol ?: inum.subvol;
+		u32 snapshot;
+
+		ret = bch2_subvolume_get_snapshot(trans, subvol, &snapshot);
+		if (ret)
+			goto err;
+
+		struct bkey_s_c_dirent d =
+			bch2_bkey_get_iter_typed(trans, &iter, BTREE_ID_dirents,
+					SPOS(inode_u.bi_dir, inode_u.bi_dir_offset, snapshot),
+					0, dirent);
+		ret = bkey_err(d);
+		if (ret)
+			goto err;
+
+		struct qstr name = bch2_dirent_get_name(d);
+		ret = darray_make_room(path, name.len);
+		if (ret)
+			goto err;
+		memreverse(&darray_top(*path), name.name, name.len);
+		path->nr += name.len;
+		bch2_trans_iter_exit(trans, &iter);
+
+		inum.inum = inode_u.bi_dir;
+		inum.subvol = subvol;
+	}
+
+	memreverse_inplace(path->data, path->nr);
+
+	ret = darray_push(path, '\0');
+err:
+	if (ret)
+		darray_exit(path);
+	bch2_trans_iter_exit(trans, &iter);
+	return ret;
+}
+
+int bch2_subvol_to_path_trans(struct btree_trans *trans, u32 subvol, darray_char *path)
+{
+	struct bch_subvolume s;
+
+	return  bch2_subvolume_get(trans, subvol, true, 0, &s) ?:
+		bch2_inum_to_path_trans(trans, (subvol_inum) { subvol, le64_to_cpu(s.inode) }, path);
+}
diff --git a/fs/bcachefs/fs-common.h b/fs/bcachefs/fs-common.h
index dde237859514..d82e4f003a21 100644
--- a/fs/bcachefs/fs-common.h
+++ b/fs/bcachefs/fs-common.h
@@ -40,4 +40,7 @@ int bch2_rename_trans(struct btree_trans *,
 bool bch2_reinherit_attrs(struct bch_inode_unpacked *,
 			  struct bch_inode_unpacked *);
 
+int bch2_inum_to_path_trans(struct btree_trans *, subvol_inum, darray_char *);
+int bch2_subvol_to_path_trans(struct btree_trans *, u32, darray_char *);
+
 #endif /* _BCACHEFS_FS_COMMON_H */
diff --git a/fs/bcachefs/fs.c b/fs/bcachefs/fs.c
index d82f7f3f0670..2a4238b8746c 100644
--- a/fs/bcachefs/fs.c
+++ b/fs/bcachefs/fs.c
@@ -32,6 +32,7 @@
 #include <linux/exportfs.h>
 #include <linux/fiemap.h>
 #include <linux/module.h>
+#include <linux/namei.h>
 #include <linux/pagemap.h>
 #include <linux/posix_acl.h>
 #include <linux/random.h>
@@ -1438,6 +1439,36 @@ static const struct export_operations bch_export_ops = {
 	.get_name	= bch2_get_name,
 };
 
+static int path_permission_check(struct vfsmount *mnt, const char *path)
+{
+	struct path vfspath;
+	int ret = vfs_path_lookup(mnt->mnt_root, mnt, path, 0, &vfspath);
+	path_put(&vfspath);
+	return ret;
+}
+
+int bch2_inum_to_path_checked(struct bch_fs *c, struct vfsmount *mnt,
+			      subvol_inum inum, darray_char *path)
+{
+	int ret = bch2_trans_do(c, NULL, NULL, 0,
+				bch2_inum_to_path_trans(trans, inum, path)) ?:
+		path_permission_check(mnt, path->data);
+	if (ret)
+		darray_exit(path);
+	return ret;
+}
+
+int bch2_subvol_to_path_checked(struct bch_fs *c, struct vfsmount *mnt,
+				u32 subvol, darray_char *path)
+{
+	int ret = bch2_trans_do(c, NULL, NULL, 0,
+				bch2_subvol_to_path_trans(trans, subvol, path)) ?:
+		path_permission_check(mnt, path->data);
+	if (ret)
+		darray_exit(path);
+	return ret;
+}
+
 static void bch2_vfs_inode_init(struct btree_trans *trans, subvol_inum inum,
 				struct bch_inode_info *inode,
 				struct bch_inode_unpacked *bi,
diff --git a/fs/bcachefs/fs.h b/fs/bcachefs/fs.h
index c3af7225ff69..8c6f9d42203d 100644
--- a/fs/bcachefs/fs.h
+++ b/fs/bcachefs/fs.h
@@ -143,6 +143,11 @@ struct bch_inode_unpacked;
 
 #ifndef NO_BCACHEFS_FS
 
+int bch2_inum_to_path_checked(struct bch_fs *, struct vfsmount *,
+			      subvol_inum, darray_char *);
+int bch2_subvol_to_path_checked(struct bch_fs *, struct vfsmount *,
+				u32, darray_char *);
+
 struct bch_inode_info *
 __bch2_create(struct mnt_idmap *, struct bch_inode_info *,
 	      struct dentry *, umode_t, dev_t, subvol_inum, unsigned);