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    Subject[178/272] slub: Avoid use of slub_lock in show_slab_objects()
    2.6.37-stable review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Christoph Lameter <cl@linux.com>

    commit 04d94879c8a4973b5499dc26b9d38acee8928791 upstream.

    The purpose of the locking is to prevent removal and additions
    of nodes when statistics are gathered for a slab cache. So we
    need to avoid racing with memory hotplug functionality.

    It is enough to take the memory hotplug locks there instead
    of the slub_lock.

    online_pages() currently does not acquire the memory_hotplug
    lock. Another patch will be submitted by the memory hotplug
    authors to take the memory hotplug lock and describe the
    uses of the memory hotplug lock to protect against
    adding and removal of nodes from non hotplug data structures.

    Reported-and-tested-by: Bart Van Assche <bvanassche@acm.org>
    Acked-by: David Rientjes <rientjes@google.com>
    Signed-off-by: Christoph Lameter <cl@linux.com>
    Signed-off-by: Pekka Enberg <penberg@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    mm/slub.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/mm/slub.c
    +++ b/mm/slub.c
    @@ -3821,7 +3821,7 @@ static ssize_t show_slab_objects(struct
    }
    }

    - down_read(&slub_lock);
    + lock_memory_hotplug();
    #ifdef CONFIG_SLUB_DEBUG
    if (flags & SO_ALL) {
    for_each_node_state(node, N_NORMAL_MEMORY) {
    @@ -3862,7 +3862,7 @@ static ssize_t show_slab_objects(struct
    x += sprintf(buf + x, " N%d=%lu",
    node, nodes[node]);
    #endif
    - up_read(&slub_lock);
    + unlock_memory_hotplug();
    kfree(nodes);
    return x + sprintf(buf + x, "\n");
    }



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