commit eebe8a8459f78bbac5a12d0ef76838929d736ad2
author Kent Overstreet <kent.overstreet@linux.dev> Sat Sep 23 16:55:03 2023 -0400
committer Kent Overstreet <kent.overstreet@linux.dev> Sun Oct 22 17:10:15 2023 -0400
tree 0eeef4900e9d5311b2114cef5110bbb991b5ac0b
parent 82142a5541063addd15c84fcda890675035df8aa

bcachefs: Make sure to initialize equiv when creating new snapshots

Previously, equiv was set in the snapshot deletion path, which is where
it's needed - equiv, for snapshot ID equivalence classes, would ideally
be a private data structure to the snapshot deletion path.

But if a new snapshot is created while snapshot deletion is running,
move_key_to_correct_snapshot() moves a key to snapshot id 0 - oops.

Fixes: https://github.com/koverstreet/bcachefs/issues/593
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/snapshot.c

diff --git a/fs/bcachefs/snapshot.c b/fs/bcachefs/snapshot.c
index f27e8c4..cdf9eda 100644
--- a/fs/bcachefs/snapshot.c
+++ b/fs/bcachefs/snapshot.c
@@ -343,7 +343,7 @@ int bch2_snapshot_lookup(struct btree_trans *trans, u32 id,
 				       BTREE_ITER_WITH_UPDATES, snapshot, s);
 }
 
-int bch2_snapshot_live(struct btree_trans *trans, u32 id)
+static int bch2_snapshot_live(struct btree_trans *trans, u32 id)
 {
 	struct bch_snapshot v;
 	int ret;
@@ -370,7 +370,7 @@ int bch2_snapshot_live(struct btree_trans *trans, u32 id)
  * it's part of such a linear chain: this correctly sets equivalence classes on
  * startup if we run leaf to root (i.e. in natural key order).
  */
-int bch2_snapshot_set_equiv(struct btree_trans *trans, struct bkey_s_c k)
+static int bch2_snapshot_set_equiv(struct btree_trans *trans, struct bkey_s_c k)
 {
 	struct bch_fs *c = trans->c;
 	unsigned i, nr_live = 0, live_idx = 0;
@@ -1071,6 +1071,10 @@ static int create_snapids(struct btree_trans *trans, u32 parent, u32 tree,
 			goto err;
 
 		new_snapids[i]	= iter.pos.offset;
+
+		mutex_lock(&c->snapshot_table_lock);
+		snapshot_t_mut(c, new_snapids[i])->equiv = new_snapids[i];
+		mutex_unlock(&c->snapshot_table_lock);
 	}
 err:
 	bch2_trans_iter_exit(trans, &iter);

fs/bcachefs/snapshot.h

diff --git a/fs/bcachefs/snapshot.h b/fs/bcachefs/snapshot.h
index dabc9b9..de215d9 100644
--- a/fs/bcachefs/snapshot.h
+++ b/fs/bcachefs/snapshot.h
@@ -235,8 +235,6 @@ int bch2_snapshot_lookup(struct btree_trans *trans, u32 id,
 			 struct bch_snapshot *s);
 int bch2_snapshot_get_subvol(struct btree_trans *, u32,
 			     struct bch_subvolume *);
-int bch2_snapshot_live(struct btree_trans *trans, u32 id);
-int bch2_snapshot_set_equiv(struct btree_trans *trans, struct bkey_s_c k);
 
 /* only exported for tests: */
 int bch2_snapshot_node_create(struct btree_trans *, u32,