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    Subject[PATCH 01/14] idr: make idr_destroy() imply idr_remove_all()
    Date
    idr is silly in quite a few ways, one of which is how it's supposed to
    be destroyed - idr_destroy() doesn't release IDs and doesn't even
    whine if the idr isn't empty. If the caller forgets idr_remove_all(),
    it simply leaks memory.

    Even ida gets this wrong and leaks memory on destruction. There is
    absoltely no reason not to call idr_remove_all() from idr_destroy().
    Nobody is abusing idr_destroy() for shrinking free layer buffer and
    continues to use idr after idr_destroy(), so it's safe to do
    remove_all from destroy.

    In the whole kernel, there is only one place where idr_remove_all() is
    legitimiately used without following idr_destroy() while there are
    quite a few places where the caller forgets either idr_remove_all() or
    idr_destroy() leaking memory.

    This patch makes idr_destroy() call idr_destroy_all() and updates the
    function description accordingly.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    ---
    lib/idr.c | 20 +++++++++++---------
    1 file changed, 11 insertions(+), 9 deletions(-)

    diff --git a/lib/idr.c b/lib/idr.c
    index 6482390..1e47832 100644
    --- a/lib/idr.c
    +++ b/lib/idr.c
    @@ -436,15 +436,6 @@ EXPORT_SYMBOL(idr_remove);
    /**
    * idr_remove_all - remove all ids from the given idr tree
    * @idp: idr handle
    - *
    - * idr_destroy() only frees up unused, cached idp_layers, but this
    - * function will remove all id mappings and leave all idp_layers
    - * unused.
    - *
    - * A typical clean-up sequence for objects stored in an idr tree will
    - * use idr_for_each() to free all objects, if necessay, then
    - * idr_remove_all() to remove all ids, and idr_destroy() to free
    - * up the cached idr_layers.
    */
    void idr_remove_all(struct idr *idp)
    {
    @@ -484,9 +475,20 @@ EXPORT_SYMBOL(idr_remove_all);
    /**
    * idr_destroy - release all cached layers within an idr tree
    * @idp: idr handle
    + *
    + * Free all id mappings and all idp_layers. After this function, @idp is
    + * completely unused and can be freed / recycled. The caller is
    + * responsible for ensuring that no one else accesses @idp during or after
    + * idr_destroy().
    + *
    + * A typical clean-up sequence for objects stored in an idr tree will use
    + * idr_for_each() to free all objects, if necessay, then idr_destroy() to
    + * free up the id mappings and cached idr_layers.
    */
    void idr_destroy(struct idr *idp)
    {
    + idr_remove_all(idp);
    +
    while (idp->id_free_cnt) {
    struct idr_layer *p = get_from_free_list(idp);
    kmem_cache_free(idr_layer_cache, p);
    --
    1.8.1


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