mm: slub: move flush_cpu_slab() invocations __free_slab() invocations out of IRQ...

mm: slub: move flush_cpu_slab() invocations __free_slab() invocations out of IRQ context

flush_all() flushes a specific SLAB cache on each CPU (where the cache is
present).  The deactivate_slab()/__free_slab() invocation happens within
IPI handler and is problematic for PREEMPT_RT.

The flush operation is not a frequent operation or a hot path.  The
per-CPU flush operation can be moved to within a workqueue.

[vbabka@suse.cz: adapt to new SLUB changes]
Link: https://lkml.kernel.org/r/20210805152000.12817-30-vbabka@suse.cz
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
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: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Pekka Enberg <penberg@kernel.org>
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>