mm/slub: move slab initialization into irq enabled region

mm/slub: move slab initialization into irq enabled region

Initializing a new slab can introduce rather large latencies because most
of the initialization runs always with interrupts disabled.

There is no point in doing so.  The newly allocated slab is not visible
yet, so there is no reason to protect it against concurrent alloc/free.

Move the expensive parts of the initialization into allocate_slab(), so
for all allocations with GFP_WAIT set, interrupts are enabled.

Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Acked-by: David Rientjes <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Sebastian Andrzej Siewior <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>