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[80.230.48.7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48e6dafa6c2sm81289945e9.5.2026.05.11.01.54.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 May 2026 01:54:38 -0700 (PDT) Date: Mon, 11 May 2026 04:54:34 -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 v6 14/30] mm: memfd: skip zeroing for zeroed hugetlb pool pages Message-ID: <8f111e92b512bf59570021fc0e71eef013289992.1778487000.git.mst@redhat.com> References: MIME-Version: 1.0 In-Reply-To: X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1 X-Mutt-Fcc: =sent X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: iLM8fnGOHdkV2KOnLCU1WDFLtG0sILwm5QnJU-Xy_rA_1778489680 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 2FDF8100011 X-Stat-Signature: giq9rxu5bp31t3zqftny8tjk885da7uj X-Rspam-User: X-HE-Tag: 1778489685-787194 X-HE-Meta: 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 FqFlnNDh 3b10YaEkLlaikfxKInUb0ZrxXnUJjZidcjoWzXSvk76dq4h0vAQXArgdrS7fHgYQG9C1NSWA4ulIQBQ7af6GfTx8jemhYVyLylME01xlo7Ff/JHA4JRXPYnpjoiHJp4X6GiSeIVFWmIrj6WlOCsAw+2MPHkHjwLhDAFcnF982WIAz+PSar8+Vk9HBYmECKpRr61+dZNrCacHOHgG/HqFdzDEojsERixTedOzs1SwjTXxIgBVFPydBJoTFJWI0Q0XhUiSYhSNafrNi9SsKHtlcenoU5CcEhPx3Xl/a+cDXK5GSIREUuX+5LpSqD2xIuDcbm5HXFdYjU9uXypqlYpyvwd+n5BxZbn0u3lwmPYF19T+VlKhZeGPDvjZRndAop2quGxJPv9jNe9Z2l7c= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: gather_surplus_pages() pre-allocates hugetlb pages into the pool during mmap. Pass __GFP_ZERO so these pages are zeroed by the buddy allocator, and HPG_zeroed is set by alloc_surplus_hugetlb_folio. Add bool *zeroed output to alloc_hugetlb_folio_reserve() so callers can check whether the pool page is known-zero. memfd's memfd_alloc_folio() uses this to skip the explicit folio_zero_user() when the page is already zero. This avoids redundant zeroing for memfd hugetlb pages that were pre-allocated into the pool and never mapped to userspace. Signed-off-by: Michael S. Tsirkin Assisted-by: Claude:claude-opus-4-6 --- include/linux/hugetlb.h | 6 ++++-- mm/hugetlb.c | 11 +++++++++-- mm/memfd.c | 14 ++++++++------ 3 files changed, 21 insertions(+), 10 deletions(-) diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 950e1702fbd8..c4e66a371fce 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -714,7 +714,8 @@ struct folio *alloc_hugetlb_folio_nodemask(struct hstate *h, int preferred_nid, nodemask_t *nmask, gfp_t gfp_mask, bool allow_alloc_fallback); struct folio *alloc_hugetlb_folio_reserve(struct hstate *h, int preferred_nid, - nodemask_t *nmask, gfp_t gfp_mask); + nodemask_t *nmask, gfp_t gfp_mask, + bool *zeroed); int hugetlb_add_to_page_cache(struct folio *folio, struct address_space *mapping, pgoff_t idx); @@ -1142,7 +1143,8 @@ static inline struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, static inline struct folio * alloc_hugetlb_folio_reserve(struct hstate *h, int preferred_nid, - nodemask_t *nmask, gfp_t gfp_mask) + nodemask_t *nmask, gfp_t gfp_mask, + bool *zeroed) { return NULL; } diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 8710366d14b7..03ad5c1e0655 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2205,7 +2205,7 @@ struct folio *alloc_buddy_hugetlb_folio_with_mpol(struct hstate *h, } struct folio *alloc_hugetlb_folio_reserve(struct hstate *h, int preferred_nid, - nodemask_t *nmask, gfp_t gfp_mask) + nodemask_t *nmask, gfp_t gfp_mask, bool *zeroed) { struct folio *folio; @@ -2221,6 +2221,12 @@ struct folio *alloc_hugetlb_folio_reserve(struct hstate *h, int preferred_nid, h->resv_huge_pages--; spin_unlock_irq(&hugetlb_lock); + + if (zeroed && folio) { + *zeroed = folio_test_hugetlb_zeroed(folio); + folio_clear_hugetlb_zeroed(folio); + } + return folio; } @@ -2305,7 +2311,8 @@ static int gather_surplus_pages(struct hstate *h, long delta) * It is okay to use NUMA_NO_NODE because we use numa_mem_id() * down the road to pick the current node if that is the case. */ - folio = alloc_surplus_hugetlb_folio(h, htlb_alloc_mask(h), + folio = alloc_surplus_hugetlb_folio(h, + htlb_alloc_mask(h) | __GFP_ZERO, NUMA_NO_NODE, &alloc_nodemask, USER_ADDR_NONE); if (!folio) { diff --git a/mm/memfd.c b/mm/memfd.c index fb425f4e315f..5518f7d2d91f 100644 --- a/mm/memfd.c +++ b/mm/memfd.c @@ -69,6 +69,7 @@ struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx) #ifdef CONFIG_HUGETLB_PAGE struct folio *folio; gfp_t gfp_mask; + bool zeroed; if (is_file_hugepages(memfd)) { /* @@ -93,17 +94,18 @@ struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx) folio = alloc_hugetlb_folio_reserve(h, numa_node_id(), NULL, - gfp_mask); + gfp_mask, + &zeroed); if (folio) { u32 hash; /* - * Zero the folio to prevent information leaks to userspace. - * Use folio_zero_user() which is optimized for huge/gigantic - * pages. Pass 0 as addr_hint since this is not a faulting path - * and we don't have a user virtual address yet. + * Zero the folio to prevent information leaks to + * userspace. Skip if the pool page is known-zero + * (HPG_zeroed set during pool pre-allocation). */ - folio_zero_user(folio, 0); + if (!zeroed) + folio_zero_user(folio, 0); /* * Mark the folio uptodate before adding to page cache, -- MST