From 77aeaa2f0fcac2d68fe1af61169fe26d5fac9a22 Mon Sep 17 00:00:00 2001
From: Kent Overstreet <kent.overstreet@linux.dev>
Date: Mon, 19 May 2025 09:48:50 -0400
Subject: [PATCH] bcachefs: bch2_inum_snapshot_to_path()

Add a better helper for printing out paths of inodes when we don't know
the subvolume, for fsck.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
 fs/bcachefs/error.c    | 22 +++-------------------
 fs/bcachefs/namei.c    | 18 ++++++++++++++++++
 fs/bcachefs/namei.h    |  2 ++
 fs/bcachefs/snapshot.c | 29 +++++++++++++++++++----------
 fs/bcachefs/snapshot.h |  2 +-
 5 files changed, 43 insertions(+), 30 deletions(-)

diff --git a/fs/bcachefs/error.c b/fs/bcachefs/error.c
index a476dd2c196eb..c2cad28635bfa 100644
--- a/fs/bcachefs/error.c
+++ b/fs/bcachefs/error.c
@@ -742,25 +742,9 @@ void bch2_inum_offset_err_msg(struct bch_fs *c, struct printbuf *out,
 int bch2_inum_snap_offset_err_msg_trans(struct btree_trans *trans, struct printbuf *out,
 					struct bpos pos)
 {
-	struct bch_fs *c = trans->c;
-	int ret = 0;
-
-	if (!bch2_snapshot_is_leaf(c, pos.snapshot))
-		prt_str(out, "(multiple snapshots) ");
-
-	subvol_inum inum = {
-		.subvol	= bch2_snapshot_tree_oldest_subvol(c, pos.snapshot),
-		.inum	= pos.inode,
-	};
-
-	if (inum.subvol) {
-		ret = bch2_inum_to_path(trans, inum, out);
-		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
-			return ret;
-	}
-
-	if (!inum.subvol || ret)
-		prt_printf(out, "inum %llu:%u", pos.inode, pos.snapshot);
+	int ret = bch2_inum_snapshot_to_path(trans, pos.inode, pos.snapshot, NULL, out);
+	if (ret)
+		return ret;
 
 	prt_printf(out, " offset %llu: ", pos.offset << 8);
 	return 0;
diff --git a/fs/bcachefs/namei.c b/fs/bcachefs/namei.c
index e81e554b51d38..8088e810815f9 100644
--- a/fs/bcachefs/namei.c
+++ b/fs/bcachefs/namei.c
@@ -654,6 +654,24 @@ disconnected:
 	goto out;
 }
 
+int bch2_inum_snapshot_to_path(struct btree_trans *trans, u64 inum, u32 snapshot,
+			       snapshot_id_list *snapshot_overwrites,
+			       struct printbuf *path)
+{
+	u32 subvol = bch2_snapshot_oldest_subvol(trans->c, snapshot, snapshot_overwrites);
+	int ret = 0;
+
+	if (subvol) {
+		ret = bch2_inum_to_path(trans, (subvol_inum) { subvol, inum }, path);
+		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
+			return ret;
+	}
+
+	if (!subvol || ret)
+		prt_printf(path, "inum %llu:%u", inum, snapshot);
+	return 0;
+}
+
 /* fsck */
 
 static int bch2_check_dirent_inode_dirent(struct btree_trans *trans,
diff --git a/fs/bcachefs/namei.h b/fs/bcachefs/namei.h
index 2e6f6364767ff..d4d2d2d69517f 100644
--- a/fs/bcachefs/namei.h
+++ b/fs/bcachefs/namei.h
@@ -43,6 +43,8 @@ bool bch2_reinherit_attrs(struct bch_inode_unpacked *,
 			  struct bch_inode_unpacked *);
 
 int bch2_inum_to_path(struct btree_trans *, subvol_inum, struct printbuf *);
+int bch2_inum_snapshot_to_path(struct btree_trans *, u64, u32,
+			       snapshot_id_list *, struct printbuf *);
 
 int __bch2_check_dirent_target(struct btree_trans *,
 			       struct btree_iter *,
diff --git a/fs/bcachefs/snapshot.c b/fs/bcachefs/snapshot.c
index 24903e7de296c..00d62d1190ef0 100644
--- a/fs/bcachefs/snapshot.c
+++ b/fs/bcachefs/snapshot.c
@@ -409,22 +409,31 @@ static u32 bch2_snapshot_tree_next(struct bch_fs *c, u32 id)
 	return 0;
 }
 
-u32 bch2_snapshot_tree_oldest_subvol(struct bch_fs *c, u32 snapshot_root)
+u32 bch2_snapshot_oldest_subvol(struct bch_fs *c, u32 snapshot_root,
+				snapshot_id_list *skip)
 {
-	u32 id = snapshot_root;
-	u32 subvol = 0, s;
-
+	u32 id, subvol = 0, s;
+retry:
+	id = snapshot_root;
 	rcu_read_lock();
 	while (id && bch2_snapshot_exists(c, id)) {
-		s = snapshot_t(c, id)->subvol;
-
-		if (s && (!subvol || s < subvol))
-			subvol = s;
+		if (!(skip && snapshot_list_has_id(skip, id))) {
+			s = snapshot_t(c, id)->subvol;
 
+			if (s && (!subvol || s < subvol))
+				subvol = s;
+		}
 		id = bch2_snapshot_tree_next(c, id);
+		if (id == snapshot_root)
+			break;
 	}
 	rcu_read_unlock();
 
+	if (!subvol && skip) {
+		skip = NULL;
+		goto retry;
+	}
+
 	return subvol;
 }
 
@@ -456,7 +465,7 @@ static int bch2_snapshot_tree_master_subvol(struct btree_trans *trans,
 	if (!ret && !found) {
 		struct bkey_i_subvolume *u;
 
-		*subvol_id = bch2_snapshot_tree_oldest_subvol(c, snapshot_root);
+		*subvol_id = bch2_snapshot_oldest_subvol(c, snapshot_root, NULL);
 
 		u = bch2_bkey_get_mut_typed(trans, &iter,
 					    BTREE_ID_subvolumes, POS(0, *subvol_id),
@@ -673,7 +682,7 @@ static int snapshot_tree_ptr_repair(struct btree_trans *trans,
 		u = bch2_bkey_make_mut_typed(trans, &root_iter, &root.s_c, 0, snapshot);
 		ret =   PTR_ERR_OR_ZERO(u) ?:
 			bch2_snapshot_tree_create(trans, root_id,
-				bch2_snapshot_tree_oldest_subvol(c, root_id),
+				bch2_snapshot_oldest_subvol(c, root_id, NULL),
 				&tree_id);
 		if (ret)
 			goto err;
diff --git a/fs/bcachefs/snapshot.h b/fs/bcachefs/snapshot.h
index 63b9469eb1ebf..382a171f54132 100644
--- a/fs/bcachefs/snapshot.h
+++ b/fs/bcachefs/snapshot.h
@@ -105,7 +105,7 @@ static inline u32 bch2_snapshot_nth_parent(struct bch_fs *c, u32 id, u32 n)
 	return id;
 }
 
-u32 bch2_snapshot_tree_oldest_subvol(struct bch_fs *, u32);
+u32 bch2_snapshot_oldest_subvol(struct bch_fs *, u32, snapshot_id_list *);
 u32 bch2_snapshot_skiplist_get(struct bch_fs *, u32);
 
 static inline u32 bch2_snapshot_root(struct bch_fs *c, u32 id)
-- 
2.39.5