rom ae060e0b7bc071bd73dd5319b93c3344d9e10212 Mon Sep 17 00:00:00 2001 From: Manfred Spraul To: torvalds@linux-foundation.org Cc: linux-kernel@vger.kernel.org Cc: cebbert@redhat.com Cc: airlied@gmail.com Cc: akpm@linux-foundation.org Bcc: manfred@colorfullife.com Date: Wed, 10 Dec 2008 18:17:06 +0100 Subject: [PATCH] lib/idr.c: Fix bug introduced by RCU fix The last patch to lib/idr.c caused a bug if idr_get_new_above() was called on an empty idr: Usually, nodes stay on the same layer. New layers are added to the top of the tree. The exception is idr_get_new_above() on an empty tree: In this case, the new root node is first added on layer 0, then moved upwards. p->layer was not updated. As usual: You shall never rely on the source code comments, they will only mislead you. Signed-off-by: Manfred Spraul --- lib/idr.c | 8 +++++++- 1 files changed, 7 insertions(+), 1 deletions(-) diff --git a/lib/idr.c b/lib/idr.c index 7a785a0..1c4f928 100644 --- a/lib/idr.c +++ b/lib/idr.c @@ -220,8 +220,14 @@ build_up: */ while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) { layers++; - if (!p->count) + if (!p->count) { + /* special case: if the tree is currently empty, + * then we grow the tree by moving the top node + * upwards. + */ + p->layer++; continue; + } if (!(new = get_from_free_list(idp))) { /* * The allocation failed. If we built part of -- 1.5.6.5