From: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> commit f806de88d8f7f8191afd0fd9b94db4cd058e7d4f upstream. The write lock should be held when validating the tree to avoid updates racing with checks. Holding the rcu read lock during a large tree validation may also cause a prolonged rcu read window and "rcu_preempt detected stalls" warnings. Link: https://lore.kernel.org/all/0000000000001d12d4062005aea1@xxxxxxxxxx/ Link: https://lkml.kernel.org/r/20240820175417.2782532-1-Liam.Howlett@xxxxxxxxxx Fixes: 54a611b60590 ("Maple Tree: add new data structure") Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> Reported-by: syzbot+036af2f0c7338a33b0cd@xxxxxxxxxxxxxxxxxxxxxxxxx Cc: Hillf Danton <hdanton@xxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- lib/maple_tree.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -7569,14 +7569,14 @@ static void mt_validate_nulls(struct map * 2. The gap is correctly set in the parents */ void mt_validate(struct maple_tree *mt) + __must_hold(mas->tree->ma_lock) { unsigned char end; MA_STATE(mas, mt, 0, 0); - rcu_read_lock(); mas_start(&mas); if (!mas_is_active(&mas)) - goto done; + return; while (!mte_is_leaf(mas.node)) mas_descend(&mas); @@ -7597,9 +7597,6 @@ void mt_validate(struct maple_tree *mt) mas_dfs_postorder(&mas, ULONG_MAX); } mt_validate_nulls(mt); -done: - rcu_read_unlock(); - } EXPORT_SYMBOL_GPL(mt_validate); Patches currently in stable-queue which might be from Liam.Howlett@xxxxxxxxxx are queue-6.10/maple_tree-remove-rcu_read_lock-from-mt_validate.patch
