[PATCH v7 2/8] mm,memory_hotplug: Relax fully spanned sections check

From: Oscar Salvador <osalvador@suse.de>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand <david@redhat.com>,
	Michal Hocko <mhocko@kernel.org>,
	Anshuman Khandual <anshuman.khandual@arm.com>,
	Pavel Tatashin <pasha.tatashin@soleen.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Oscar Salvador <osalvador@suse.de>
Subject: [PATCH v7 2/8] mm,memory_hotplug: Relax fully spanned sections check
Date: Thu,  8 Apr 2021 14:17:58 +0200	[thread overview]
Message-ID: <20210408121804.10440-3-osalvador@suse.de> (raw)
In-Reply-To: <20210408121804.10440-1-osalvador@suse.de>

When using self-hosted vmemmap pages, the number of pages passed to
{online,offline}_pages might not fully span sections, but they always
fully span pageblocks.
Relax the check account for that case.

Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
 mm/memory_hotplug.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 0cdbbfbc5757..25e59d5dc13c 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -838,9 +838,14 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
 	int ret;
 	struct memory_notify arg;
 
-	/* We can only online full sections (e.g., SECTION_IS_ONLINE) */
+	/* We can only offline full sections (e.g., SECTION_IS_ONLINE).
+	 * However, when using e.g: memmap_on_memory, some pages are initialized
+	 * prior to calling in here. The remaining amount of pages must be
+	 * pageblock aligned.
+	 */
 	if (WARN_ON_ONCE(!nr_pages ||
-			 !IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION)))
+			 !IS_ALIGNED(pfn, pageblock_nr_pages) ||
+			 !IS_ALIGNED(pfn + nr_pages, PAGES_PER_SECTION)))
 		return -EINVAL;
 
 	mem_hotplug_begin();
@@ -1573,9 +1578,14 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
 	int ret, node;
 	char *reason;
 
-	/* We can only offline full sections (e.g., SECTION_IS_ONLINE) */
+	/* We can only offline full sections (e.g., SECTION_IS_ONLINE).
+	 * However, when using e.g: memmap_on_memory, some pages are initialized
+	 * prior to calling in here. The remaining amount of pages must be
+	 * pageblock aligned.
+	 */
 	if (WARN_ON_ONCE(!nr_pages ||
-			 !IS_ALIGNED(start_pfn | nr_pages, PAGES_PER_SECTION)))
+			 !IS_ALIGNED(start_pfn, pageblock_nr_pages) ||
+			 !IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION)))
 		return -EINVAL;
 
 	mem_hotplug_begin();
-- 
2.16.3

