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    Subject[PATCH 1/2] cgroup/kmemleak: Annotate alloc_page() for cgroup allocations
    From: Steven Rostedt <rostedt@goodmis.org>
    Date: Tue, 26 Jul 2011 15:19:16 -0400

    When the cgroup base was allocated with kmalloc, it was necessary to
    annotate the variable with kmemleak_not_leak(). But because it has
    recently been changed to be allocated with alloc_page() (which skips
    kmemleak checks) causes a warning on boot up.

    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
    displayed.

    If alloc_page() fails then it defaults back to vmalloc() which still
    uses the kmemleak_alloc() which makes us still need the
    kmemleak_not_leak() call. The solution is to call the kmemleak_alloc()
    directly if the alloc_page() succeeds.

    Reviewed-by: Michal Hocko <mhocko@suse.cz>
    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    Acked-by: Catalin Marinas <catalin.marinas@arm.com>
    Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
    ---
    This patch is taken from [1]. The only change I made is to correct
    "kmemcheck" above to "kmemleak" as suggested by Catalin. Seems to
    work ok. :)

    [1] http://thread.gmane.org/gmane.linux.kernel/1171696/focus=1178619

    mm/page_cgroup.c | 7 +++++--
    1 files changed, 5 insertions(+), 2 deletions(-)

    diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
    index 39d216d535ea..95e564cfe788 100644
    --- a/mm/page_cgroup.c
    +++ b/mm/page_cgroup.c
    @@ -133,10 +133,13 @@ struct page *lookup_cgroup_page(struct page_cgroup *pc)
    static void *__meminit alloc_page_cgroup(size_t size, int nid)
    {
    void *addr = NULL;
    + gfp_t flags = GFP_KERNEL | __GFP_NOWARN;

    - addr = alloc_pages_exact_nid(nid, size, GFP_KERNEL | __GFP_NOWARN);
    - if (addr)
    + addr = alloc_pages_exact_nid(nid, size, flags);
    + if (addr) {
    + kmemleak_alloc(addr, size, 1, flags);
    return addr;
    + }

    if (node_state(nid, N_HIGH_MEMORY))
    addr = vmalloc_node(size, nid);
    --
    1.7.7.rc1


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