FROMLIST: BACKPORT: mm/page_alloc: Protect PCP lists with a spinlock

Currently the PCP lists are protected by using local_lock_irqsave to
prevent migration and IRQ reentrancy but this is inconvenient. Remote
draining of the lists is impossible and a workqueue is required and
every task allocation/free must disable then enable interrupts which is
expensive.

As preparation for dealing with both of those problems, protect the
lists with a spinlock. The IRQ-unsafe version of the lock is used
because IRQs are already disabled by local_lock_irqsave. spin_trylock
is used in preparation for a time when local_lock could be used instead
of lock_lock_irqsave.

The per_cpu_pages still fits within the same number of cache lines after
this patch relative to before the series.

struct per_cpu_pages {
    spinlock_t                 lock;                 /*     0     4 */
    int                        count;                /*     4     4 */
    int                        high;                 /*     8     4 */
    int                        batch;                /*    12     4 */
    short int                  free_factor;          /*    16     2 */
    short int                  expire;               /*    18     2 */

    /* XXX 4 bytes hole, try to pack */

    struct list_head           lists[13];            /*    24   208 */

    /* size: 256, cachelines: 4, members: 7 */
    /* sum members: 228, holes: 1, sum holes: 4 */
    /* padding: 24 */
} __attribute__((__aligned__(64)));

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Link: https://lore.kernel.org/all/20220420095906.27349-6-mgorman@techsingularity.net/
Link: https://lore.kernel.org/all/20220429091321.GB3441@techsingularity.net/



Conflicts:
	mm/page_alloc.c

1. per_cpu_pages are updated from 44042b44 at 5.13 so conflicted
Since we don't need to have high-order page pcp atm, skip the patch.

Bug: 230899966
Signed-off-by: Minchan Kim <minchan@google.com>
Change-Id: I03ff1c22301e7f8735947e71413376ea143e855a