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    Subject[PATCH] cgroup/kmemcheck: No need to annotate base anymore
    When the cgroup base was allocated with kmalloc, it was necessary to
    annotate the variable with kmemcheck_not_leak(). But because it has
    recently been changed to be allocated with alloc_page(), the annotation
    is no longer needed.

    I was triggering this output:

    allocated 8388608 bytes of page_cgroup
    please try 'cgroup_disable=memory' option if you don't want memory cgroups
    kmemleak: Trying to color unknown object at 0xf5840000 as Grey
    Pid: 0, comm: swapper Not tainted 3.0.0-test #12
    Call Trace:
    [<c17e34e6>] ? printk+0x1d/0x1f^M
    [<c10e2941>] paint_ptr+0x4f/0x78
    [<c178ab57>] kmemleak_not_leak+0x58/0x7d
    [<c108ae9f>] ? __rcu_read_unlock+0x9/0x7d
    [<c1cdb462>] kmemleak_init+0x19d/0x1e9
    [<c1cbf771>] start_kernel+0x346/0x3ec
    [<c1cbf1b4>] ? loglevel+0x18/0x18
    [<c1cbf0aa>] i386_start_kernel+0xaa/0xb0

    After a bit of debugging I tracked the object 0xf840000 (and others)
    down to the cgroup code. The change from allocating base with kmalloc to
    alloc_page() has the base not calling kmemleak_alloc() which adds the
    pointer to the object_tree_root, but kmemleak_not_leak() adds it to the
    crt_early_log[] table. On kmemleak_init(), the entry is found in the
    early_log[] but not the object_tree_root, and this error message is

    Signed-off-by: Steven Rostedt <>

    diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
    index 53bffc6..955a49f 100644
    --- a/mm/page_cgroup.c
    +++ b/mm/page_cgroup.c
    @@ -9,7 +9,6 @@
    #include <linux/vmalloc.h>
    #include <linux/cgroup.h>
    #include <linux/swapops.h>
    -#include <linux/kmemleak.h>

    static void __meminit init_page_cgroup(struct page_cgroup *pc, unsigned long id)
    @@ -179,13 +178,6 @@ static int __meminit init_section_page_cgroup(unsigned long pfn, int nid)
    table_size = sizeof(struct page_cgroup) * PAGES_PER_SECTION;
    base = alloc_page_cgroup(table_size, nid);

    - /*
    - * The value stored in section->page_cgroup is (base - pfn)
    - * and it does not point to the memory block allocated above,
    - * causing kmemleak false positives.
    - */
    - kmemleak_not_leak(base);
    if (!base) {
    printk(KERN_ERR "page cgroup allocation failure\n");
    return -ENOMEM;

     \ /
      Last update: 2011-07-26 19:07    [W:0.021 / U:20.468 seconds]
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