Commit 711a49a0 authored by Manfred Spraul's avatar Manfred Spraul Committed by Linus Torvalds
Browse files

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: default avatarManfred Spraul <>
Signed-off-by: default avatarLinus Torvalds <>
parent c7f8d6f6
......@@ -220,8 +220,14 @@ static int idr_get_empty_slot(struct idr *idp, int starting_id,
while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
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.
if (!(new = get_from_free_list(idp))) {
* The allocation failed. If we built part of
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