linux-kernel - [PATCH] mm: be more verbose for alloc_contig

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Date:   Wed, 17 Feb 2021 08:36:03 -0800
From:   Minchan Kim <minchan@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
        mhocko@...e.com, david@...hat.com, joaodias@...gle.com,
        Minchan Kim <minchan@...nel.org>
Subject: [PATCH] mm: be more verbose for alloc_contig_range faliures

alloc_contig_range is usually used on cma area or movable zone.
It's critical if the page migration fails on those areas so
dump more debugging message like memory_hotplug unless user
specifiy __GFP_NOWARN.

Signed-off-by: Minchan Kim <minchan@...nel.org>
---
 mm/page_alloc.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0b55c9c95364..67f3ee3a1528 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8486,6 +8486,15 @@ static int __alloc_contig_migrate_range(struct compact_control *cc,
 				NULL, (unsigned long)&mtc, cc->mode, MR_CONTIG_RANGE);
 	}
 	if (ret < 0) {
+		if (!(cc->gfp_mask & __GFP_NOWARN)) {
+			struct page *page;
+
+			list_for_each_entry(page, &cc->migratepages, lru) {
+				pr_warn("migrating pfn %lx failed ret:%d ",
+						page_to_pfn(page), ret);
+				dump_page(page, "migration failure");
+			}
+		}
 		putback_movable_pages(&cc->migratepages);
 		return ret;
 	}
@@ -8728,6 +8737,8 @@ struct page *alloc_contig_pages(unsigned long nr_pages, gfp_t gfp_mask,
 		pfn = ALIGN(zone->zone_start_pfn, nr_pages);
 		while (zone_spans_last_pfn(zone, pfn, nr_pages)) {
 			if (pfn_range_valid_contig(zone, pfn, nr_pages)) {
+				unsigned long gfp_flags;
+
 				/*
 				 * We release the zone lock here because
 				 * alloc_contig_range() will also lock the zone
@@ -8736,8 +8747,11 @@ struct page *alloc_contig_pages(unsigned long nr_pages, gfp_t gfp_mask,
 				 * and cause alloc_contig_range() to fail...
 				 */
 				spin_unlock_irqrestore(&zone->lock, flags);
+
+				if (zone_idx(zone) != ZONE_MOVABLE)
+					gfp_flags = gfp_mask | __GFP_NOWARN;
 				ret = __alloc_contig_pages(pfn, nr_pages,
-							gfp_mask);
+							gfp_flags);
 				if (!ret)
 					return pfn_to_page(pfn);
 				spin_lock_irqsave(&zone->lock, flags);
-- 
2.30.0.478.g8a0d178c01-goog