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    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 <manfred@colorfullife.com>
    ---
    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


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