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[80.230.48.7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48e65d1367bsm3470575e9.31.2026.05.07.15.23.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 May 2026 15:23:31 -0700 (PDT) Date: Thu, 7 May 2026 18:23:29 -0400 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: Andrew Morton , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , linux-mm@kvack.org Subject: [PATCH v5 22/28] mm: page_alloc: propagate PG_zeroed in split_large_buddy Message-ID: 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 a large zeroed page is freed with order > pageblock_order, split_large_buddy splits it into pageblock-sized pieces. Propagate PG_zeroed from the head page to each sub-block head so the zeroed hint is not lost. The propagation reads PageZeroed from the head page (set by __free_pages_ok before calling free_one_page) rather than from FPI_ZEROED, to avoid incorrectly marking deferred pages that share the same code path but may not be zeroed. For order-0 frees this is a single-iteration no-op (the head already has the flag). For higher-order frees it ensures all sub-block heads inherit the zeroed hint. Signed-off-by: Michael S. Tsirkin Assisted-by: Claude:claude-opus-4-6 --- mm/page_alloc.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 5c6ab949855a..954d86655f77 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1554,6 +1554,7 @@ 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! */ @@ -1565,6 +1566,8 @@ 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) @@ -1624,8 +1627,11 @@ static void __free_pages_ok(struct page *page, unsigned int order, unsigned long pfn = page_to_pfn(page); struct zone *zone = page_zone(page); - if (__free_pages_prepare(page, order, fpi_flags)) + if (__free_pages_prepare(page, order, fpi_flags)) { + if (fpi_flags & FPI_ZEROED) + __SetPageZeroed(page); free_one_page(zone, page, pfn, order, fpi_flags); + } } void __meminit __free_pages_core(struct page *page, unsigned int order, -- MST