mm, slub: call deactivate_slab() without disabling irqs

mm, slub: call deactivate_slab() without disabling irqs

The function is now safe to be called with irqs enabled, so move the calls
outside of irq disabled sections.

When called from ___slab_alloc() -> flush_slab() we have irqs disabled, so
to reenable them before deactivate_slab() we need to open-code
flush_slab() in ___slab_alloc() and reenable irqs after modifying the
kmem_cache_cpu fields.  But that means a IRQ handler meanwhile might have
assigned a new page to kmem_cache_cpu.page so we have to retry the whole
check.

The remaining callers of flush_slab() are the IPI handler which has
disabled irqs anyway, and slub_cpu_dead() which will be dealt with in the
following patch.

Link: https://lkml.kernel.org/r/20210805152000.12817-22-vbabka@suse.cz
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: 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>