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authorKent Overstreet <kent.overstreet@linux.dev>2024-04-13 18:39:03 -0400
committerKent Overstreet <kent.overstreet@linux.dev>2024-04-13 22:49:25 -0400
commit3f10048973c8366e27147d72bf3fd8d0e1d929f2 (patch)
tree0d958fc944434c2fed78c233146e0dc917da37d6
parent9054ef2ea944528b7935d0ce3f540d4dc0bc37ba (diff)
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 <kent.overstreet@linux.dev>
-rw-r--r--fs/bcachefs/btree_update_interior.c10
1 files changed, 10 insertions, 0 deletions
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;