mm, slub: allocate private object map for debugfs listings

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.

Link: https://lkml.kernel.org/r/20210805152000.12817-3-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>