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[80.230.48.7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4549120eb95sm34339020f8f.20.2026.05.12.14.07.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 May 2026 14:07:25 -0700 (PDT) Date: Tue, 12 May 2026 17:07:20 -0400 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: "David Hildenbrand (Arm)" , Jason Wang , Xuan Zhuo , Eugenio =?utf-8?B?UMOpcmV6?= , Muchun Song , Oscar Salvador , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Hugh Dickins , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Axel Rasmussen , Yuanchu Xie , Wei Xu , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , virtualization@lists.linux.dev, linux-mm@kvack.org, Andrea Arcangeli Subject: [PATCH v7 25/31] mm: page_alloc: propagate PG_zeroed in split_large_buddy Message-ID: <2db0d124c647e711c0bf95b1c7f1316a0d1408ae.1778616612.git.mst@redhat.com> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1 X-Mutt-Fcc: =sent When splitting a large buddy page, propagate the PG_zeroed flag to each sub-page before freeing it. __free_pages_prepare clears all flags (including PG_zeroed), so the flag must be re-set on each fragment after the split. This ensures that the buddy merge logic can see PG_zeroed on pages that were part of a larger zeroed block. Signed-off-by: Michael S. Tsirkin Assisted-by: Claude:claude-opus-4-6 Assisted-by: cursor-agent:GPT-5.4-xhigh --- mm/page_alloc.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 468e8bde7d34..ce43f5a3dbaa 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1523,6 +1523,7 @@ static void split_large_buddy(struct zone *zone, struct page *page, unsigned long pfn, int order, fpi_t fpi) { unsigned long end = pfn + (1 << order); + bool zeroed = PageZeroed(page); VM_WARN_ON_ONCE(!IS_ALIGNED(pfn, 1 << order)); /* Caller removed page from freelist, buddy info cleared! */ @@ -1534,6 +1535,8 @@ static void split_large_buddy(struct zone *zone, struct page *page, do { int mt = get_pfnblock_migratetype(page, pfn); + if (zeroed) + __SetPageZeroed(page); __free_one_page(page, pfn, zone, order, mt, fpi); pfn += 1 << order; if (pfn == end) -- MST