From 3f10048973c8366e27147d72bf3fd8d0e1d929f2 Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Sat, 13 Apr 2024 18:39:03 -0400 Subject: bcachefs: Disable merges from interior update path There's been a bug in the btree write buffer where it wasn't triggering btree node merges - and leaving behind a bunch of nearly empty btree nodes. Then during journal replay, when updates to the backpointers btree aren't using the btree write buffer (because we require synchronization with journal replay), we end up doing those merges all at once. Then if it's the interior update path running them, we deadlock because those run with the highest watermark. There's no real need for the interior update path to be doing btree node merges; other code paths can handle that at lower watermarks. Signed-off-by: Kent Overstreet --- fs/bcachefs/btree_update_interior.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/fs/bcachefs/btree_update_interior.c b/fs/bcachefs/btree_update_interior.c index 1a7537ee4329..82ac00aa0f7b 100644 --- a/fs/bcachefs/btree_update_interior.c +++ b/fs/bcachefs/btree_update_interior.c @@ -1926,6 +1926,16 @@ int __bch2_foreground_maybe_merge(struct btree_trans *trans, BUG_ON(!trans->paths[path].should_be_locked); BUG_ON(!btree_node_locked(&trans->paths[path], level)); + /* + * Work around a deadlock caused by the btree write buffer not doing + * merges and leaving tons of merges for us to do - we really don't need + * to be doing merges at all from the interior update path, and if the + * interior update path is generating too many new interior updates we + * deadlock: + */ + if ((flags & BCH_WATERMARK_MASK) == BCH_WATERMARK_interior_updates) + return 0; + flags &= ~BCH_WATERMARK_MASK; b = trans->paths[path].l[level].b; -- cgit v1.2.3