From 50625744220c101705a989d7c57a6c16e945f3b1 Mon Sep 17 00:00:00 2001
From: David Hildenbrand <david@redhat.com>
Date: Fri, 7 Jun 2024 11:09:38 +0200
Subject: mm/memory_hotplug: skip adjust_managed_page_count() for PageOffline()
 pages when offlining
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We currently have a hack for virtio-mem in place to handle memory
offlining with PageOffline pages for which we already adjusted the managed
page count.

Let's enlighten memory offlining code so we can get rid of that hack, and
document the situation.

Link: https://lkml.kernel.org/r/20240607090939.89524-4-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Oscar Salvador <osalvador@suse.de>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Eugenio Pérez <eperezma@redhat.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Marco Elver <elver@google.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 mm/page_alloc.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

(limited to 'mm/page_alloc.c')

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7bc43cf24e3d..ee3b370f85c5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6716,14 +6716,19 @@ void zone_pcp_reset(struct zone *zone)
 /*
  * All pages in the range must be in a single zone, must not contain holes,
  * must span full sections, and must be isolated before calling this function.
+ *
+ * Returns the number of managed (non-PageOffline()) pages in the range: the
+ * number of pages for which memory offlining code must adjust managed page
+ * counters using adjust_managed_page_count().
  */
-void __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
+unsigned long __offline_isolated_pages(unsigned long start_pfn,
+		unsigned long end_pfn)
 {
+	unsigned long already_offline = 0, flags;
 	unsigned long pfn = start_pfn;
 	struct page *page;
 	struct zone *zone;
 	unsigned int order;
-	unsigned long flags;
 
 	offline_mem_sections(pfn, end_pfn);
 	zone = page_zone(pfn_to_page(pfn));
@@ -6745,6 +6750,7 @@ void __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
 		if (PageOffline(page)) {
 			BUG_ON(page_count(page));
 			BUG_ON(PageBuddy(page));
+			already_offline++;
 			pfn++;
 			continue;
 		}
@@ -6757,6 +6763,8 @@ void __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
 		pfn += (1 << order);
 	}
 	spin_unlock_irqrestore(&zone->lock, flags);
+
+	return end_pfn - start_pfn - already_offline;
 }
 #endif
 
-- 
cgit