From: Daniel Jordan daniel.m.jordan@oracle.com Subject: mm/pagealloc.c: call touch_nmi_watchdog() on max order boundaries in deferred init

Patch series "initialize deferred pages with interrupts enabled", v4.

Keep interrupts enabled during deferred page initialization in order to make code more modular and allow jiffies to update.

Original approach, and discussion can be found here: http://lkml.kernel.org/r/20200311123848.118638-1-shile.zhang@linux.alibaba.c...

This patch (of 3):

deferred_init_memmap() disables interrupts the entire time, so it calls touch_nmi_watchdog() periodically to avoid soft lockup splats. Soon it will run with interrupts enabled, at which point cond_resched() should be used instead.

deferred_grow_zone() makes the same watchdog calls through code shared with deferred init but will continue to run with interrupts disabled, so it can't call cond_resched().

Pull the watchdog calls up to these two places to allow the first to be changed later, independently of the second. The frequency reduces from twice per pageblock (init and free) to once per max order block.

Link: http://lkml.kernel.org/r/20200403140952.17177-2-pasha.tatashin@soleen.com Fixes: 3a2d7fa8a3d5 ("mm: disable interrupts while initializing deferred pages") Signed-off-by: Daniel Jordan daniel.m.jordan@oracle.com Signed-off-by: Pavel Tatashin pasha.tatashin@soleen.com Reviewed-by: David Hildenbrand david@redhat.com Acked-by: Michal Hocko mhocko@suse.com Acked-by: Vlastimil Babka vbabka@suse.cz Cc: Dan Williams dan.j.williams@intel.com Cc: Shile Zhang shile.zhang@linux.alibaba.com Cc: Kirill Tkhai ktkhai@virtuozzo.com Cc: James Morris jmorris@namei.org Cc: Sasha Levin sashal@kernel.org Cc: Yiqian Wei yiwei@redhat.com Cc: stable@vger.kernel.org [4.17+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/page_alloc.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/mm/page_alloc.c~mm-call-touch_nmi_watchdog-on-max-order-boundaries-in-deferred-init +++ a/mm/page_alloc.c @@ -1693,7 +1693,6 @@ static void __init deferred_free_pages(u } else if (!(pfn & nr_pgmask)) { deferred_free_range(pfn - nr_free, nr_free); nr_free = 1; - touch_nmi_watchdog(); } else { nr_free++; } @@ -1723,7 +1722,6 @@ static unsigned long __init deferred_in continue; } else if (!page || !(pfn & nr_pgmask)) { page = pfn_to_page(pfn); - touch_nmi_watchdog(); } else { page++; } @@ -1863,8 +1861,10 @@ static int __init deferred_init_memmap(v * that we can avoid introducing any issues with the buddy * allocator. */ - while (spfn < epfn) + while (spfn < epfn) { nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn); + touch_nmi_watchdog(); + } zone_empty: pgdat_resize_unlock(pgdat, &flags);

@@ -1948,6 +1948,7 @@ deferred_grow_zone(struct zone *zone, un first_deferred_pfn = spfn;

nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn); + touch_nmi_watchdog();

/* We should only stop along section boundaries */ if ((first_deferred_pfn ^ spfn) < PAGES_PER_SECTION) _