UPSTREAM: mm, slub: allocate private object map for debugfs listings

Slub has a static spinlock protected bitmap for marking which objects are on
freelist when it wants to list them, for situations where dynamically
allocating such map can lead to recursion or locking issues, and on-stack
bitmap would be too large.

The handlers of debugfs files alloc_traces and free_traces also currently use this
shared bitmap, but their syscall context makes it straightforward to allocate a
private map before entering locked sections, so switch these processing paths
to use a private bitmap.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>

Bug: 209932470
(cherry picked from commit b3fd64e1)
Change-Id: I5fbf34e0d828d1c8b5e81e3679f81b70ce1fc8bc
Signed-off-by: Yee Lee <yee.lee@mediatek.com>