fix: mm, tracing: record slab name for kmem_cache_free() (v5.12)

fix: mm, tracing: record slab name for kmem_cache_free() (v5.12)

See upstream commit:

  commit 3544de8ee6e4817278b15fe08658de49abf58954
  Author: Jacob Wen <jian.w.wen@oracle.com>
  Date:   Wed Feb 24 12:00:55 2021 -0800

    mm, tracing: record slab name for kmem_cache_free()

    Currently, a trace record generated by the RCU core is as below.

    ... kmem_cache_free: call_site=rcu_core+0x1fd/0x610 ptr=00000000f3b49a66

    It doesn't tell us what the RCU core has freed.

    This patch adds the slab name to trace_kmem_cache_free().
    The new format is as follows.

    ... kmem_cache_free: call_site=rcu_core+0x1fd/0x610 ptr=0000000037f79c8d name=dentry
    ... kmem_cache_free: call_site=rcu_core+0x1fd/0x610 ptr=00000000f78cb7b5 name=sock_inode_cache
    ... kmem_cache_free: call_site=rcu_core+0x1fd/0x610 ptr=0000000018768985 name=pool_workqueue
    ... kmem_cache_free: call_site=rcu_core+0x1fd/0x610 ptr=000000006a6cb484 name=radix_tree_node

    We can use it to understand what the RCU core is going to free. For
    example, some users maybe interested in when the RCU core starts
    freeing reclaimable slabs like dentry to reduce memory pressure.

Link: https://lkml.kernel.org/r/20201216072804.8838-1-jian.w.wen@oracle.com
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I1ee2fc476614cadcc8d3ac5d8feddc7910e1aa3a