From bf3efff5e4fc2dcd6e6c15578d3f08c301a13229 Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Sun, 27 Feb 2022 09:56:33 -0500 Subject: bcachefs: Fix race leading to btree node write getting stuck Checking btree_node_may_write() isn't atomic with the other btree flags, dirty and need_write in particular. There was a rare race where we'd unblock a node from writing while __btree_node_flush() was setting need_write, and no thread would notice that the node was now both able to write and needed to be written. Fix this by adding btree node flags for will_make_reachable and write_blocked that can be checked in the cmpxchg loop in __bch2_btree_node_write. Signed-off-by: Kent Overstreet --- fs/bcachefs/btree_cache.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) (limited to 'fs/bcachefs/btree_cache.c') diff --git a/fs/bcachefs/btree_cache.c b/fs/bcachefs/btree_cache.c index 7b264619c276..5f96c5d1a064 100644 --- a/fs/bcachefs/btree_cache.c +++ b/fs/bcachefs/btree_cache.c @@ -223,10 +223,9 @@ wait_on_io: goto wait_on_io; } - if (btree_node_noevict(b)) - goto out_unlock; - - if (!btree_node_may_write(b)) + if (btree_node_noevict(b) || + btree_node_write_blocked(b) || + btree_node_will_make_reachable(b)) goto out_unlock; if (btree_node_dirty(b)) { -- cgit v1.2.3