From 83d539b1b04705f972b53b4669fb587c54def0db Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Wed, 2 Apr 2025 14:31:12 -0400 Subject: [PATCH] bcachefs: Fix check_snapshot_exists() restart handling Codepaths that create entries in the snapshots btree currently call bch2_mark_snapshot(), which updates the in-memory snapshot table, before transaction commit. This is because bch2_mark_snapshot() is an atomic trigger, run with btree write locks held, and isn't allowed to fail - but it might need to reallocate the table, hence we call it early when we're still allowed to fail. This is generally harmless - if we fail, we'll have left an entry in the snapshots table around, but nothing will reference it and it'll get overwritten if reused by another transaction. But check_snapshot_exists(), which reconstructs snapshots when the snapshots btree has been corrupted or lost, was erronously rechecking if the snapshot exists inside the transaction commit loop - so on transaction restart (in this case mem_realloced), the second iteration would return without repairing. This code needs some cleanup: splitting out a "maybe realloc snapshots table" helper would have avoided this, that will be in the next patch. Signed-off-by: Kent Overstreet --- fs/bcachefs/snapshot.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/fs/bcachefs/snapshot.c b/fs/bcachefs/snapshot.c index c8536eb36060..b7de29aed839 100644 --- a/fs/bcachefs/snapshot.c +++ b/fs/bcachefs/snapshot.c @@ -843,9 +843,6 @@ static int check_snapshot_exists(struct btree_trans *trans, u32 id) { struct bch_fs *c = trans->c; - if (bch2_snapshot_exists(c, id)) - return 0; - /* Do we need to reconstruct the snapshot_tree entry as well? */ struct btree_iter iter; struct bkey_s_c k; -- 2.25.1