From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 022473BAD82 for ; Mon, 11 May 2026 08:54:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778489669; cv=none; b=bh+u8DSQ9pHtbCNY5nzaNZXMJ0BT8UpOlCdSdtM+hhCqZRybTzue5wanc8bPuJwB3eRQKw29a5P7pSa1J/FWlxh2mLR0eh1QptmIspVCfzLL1RQ9lxG6ms7hQtGST+eyITAeEqzwFMUA0HNXgxYIvJfmXuJeecxpha7XO68ZtKs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778489669; c=relaxed/simple; bh=nhIdqHx7RVXN0ISM6az/8nnv+4RiBG53oCOcvaW262c=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KT/ZUewxCH7Z+c7LC+s0DnIajpjEVc6KgWeHPFLMQT1dA222MkLFO2hmyXxE8yeJ9b0aAYf2wqjO4Kdg3JGShghckOTW9nleqPRLLnFfu/iqcJ5CnMcA2nFqGcDv9ChljllHbpT758GSRBB4MZ2IIOonlRcq1BRPf7pYcthRlnY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=E7MOHO6p; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=flXgyOIN; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="E7MOHO6p"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="flXgyOIN" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1778489667; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=HSkauV/IjsYyN3rKw556EWRQycHO+B2Bstj+Uf0KUNg=; b=E7MOHO6pHYqPNs6AY9cf2I0uWd1oazsIVznURSfRbctAVHeRtdQGx2JiZP2k410/GjpXO4 gDsXYfK/tOWl+WMhV+swGcTd5wrtp6lAM0yeF3W+vl26rMlDqUVaXeVUvqCds9YoHgLKMN bUQL8W4/lcShfTz55mBDbsiQaVAXN0A= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-655-YaY7MXTYO4iQO8I_VDmUIA-1; Mon, 11 May 2026 04:54:26 -0400 X-MC-Unique: YaY7MXTYO4iQO8I_VDmUIA-1 X-Mimecast-MFC-AGG-ID: YaY7MXTYO4iQO8I_VDmUIA_1778489665 Received: by mail-wr1-f70.google.com with SMTP id ffacd0b85a97d-43d7730e9e3so2633559f8f.2 for ; Mon, 11 May 2026 01:54:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1778489665; x=1779094465; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=HSkauV/IjsYyN3rKw556EWRQycHO+B2Bstj+Uf0KUNg=; b=flXgyOINGlA1TjieOUKbrJCWU3wTfSVmTl63dzOLnMCiDmT+YmnBBgzW5UoxrornoV hBrHzIWPiAfx0pEvgIj89X5zdxxMA9aB9NfEEnqRdWaxszb8u5fZeFXv1cXGbc2jTJ4M ZlIwqmlbX7wrmP7ZXAk0MsQNC31UG0R6CbMw495wgqA8ANhhiIMzNkTUGSCz1ivhbfv6 eZ6IQzN4knyjaVlYs2KGwm7QfYNMnS/r4XuTaix9NUjkCklB6p07tDyDtuQPtuY4KWQS WF6c3VEU/ZbX0+V/qO5dC27hLGWO894tBXydGlP8lwtgHdB5FOeo1LO+NmR7pT2EBHdu gx7w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778489665; x=1779094465; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=HSkauV/IjsYyN3rKw556EWRQycHO+B2Bstj+Uf0KUNg=; b=oNIAGLKOCfAGbAwOzj9mCsQCJpZvySgof2XulskPmU5DM1njtpZjWanRFO8qNS5bNr S8FzzINRnFb3Y0/RJNFets0s27Ai9GR1Tubf+8eQGowpMLXNJre6hjYMkzs+x8zcpe1r LpQCBhIbqB3KalM2t7MAUSif2pijsQtee9I1UIg1KAajWbIvLg8gFO5LD6Vv2F+yEMTz /ggUEruIYcgJ4T7gH7Y9qbJnirurrRxGO0z1R5hS2MHir7cjWYKxW5oPs5hfIveO/Ghy EcRomzTMozc0CTWVl2huHavwfinZ6+qc+NCxX4KPD5gNQuzRVxNU0Wj0Go6XBRoivglX Weow== X-Gm-Message-State: AOJu0YzhJ2G50QmGTBEvDN+Qm4tfFsx1enUI+X6yZSjoOkex62j7lVTR tvDSC1tFMCX9nvLYy3W9xDNbwNxyTHxNKK3IR4hcrB3pxyPIbIwZccDE+j941QodsnsfOcOL6My B2GkaXgS6eK5Ggyeys1cma+nJOdTTtVqY61Md857muJJHEgqoAm+us4DoeZK0FFWkx4ftk3EXJI hs/xJ2In+D53F1qMdISoRz/ZzeONhJ5k1RBioRiW70OG0JYQ== X-Gm-Gg: Acq92OGLqCEQ6Di9bClYswb6iDOA62RqF/ewgxiNjdIlxcTx1QWctu3pWa/WL9tqz8O jdD3NTEUJ1M/1nQFe8bWkhcsDNUu/Xehd2S/64XxKnUBcOvcPRWchG4yb0nSc7KLEV7tDyoRpdt sNXeCQ7+QPV6O8eDlWpQkuoo88888DJHA5UOHwoLSsTbZ/yGEGq+MyayiVynpDvjrQtqRqegC96 FQYKJbDXNmK5tc4MGKdvOESe1KOin/I0+VzdNgWoYGXIPrOoCg2gI2xOIU6UGOfXCEdcV2PBUyF KqjHdSRV+WTi+tqARwbEjpVRlUa6MqM8i+TDRqa2SiC20XtSxA6qErqRw9csQimLghcbJ+8tTCU otdNtwA1h5eFVevowaVn3lWMtZIDicqoxxD6R71Dq X-Received: by 2002:a05:6000:2309:b0:43d:4b00:9ee7 with SMTP id ffacd0b85a97d-4515cc31df6mr38451266f8f.33.1778489664407; Mon, 11 May 2026 01:54:24 -0700 (PDT) X-Received: by 2002:a05:6000:2309:b0:43d:4b00:9ee7 with SMTP id ffacd0b85a97d-4515cc31df6mr38451128f8f.33.1778489663387; Mon, 11 May 2026 01:54:23 -0700 (PDT) Received: from redhat.com (IGLD-80-230-48-7.inter.net.il. [80.230.48.7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4548ec6b071sm23662062f8f.14.2026.05.11.01.54.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 May 2026 01:54:22 -0700 (PDT) Date: Mon, 11 May 2026 04:54:18 -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 13/30] mm: hugetlb: use __GFP_ZERO and skip zeroing for zeroed pages 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 Convert the hugetlb fault and fallocate paths to use __GFP_ZERO. For pages allocated from the buddy allocator, post_alloc_hook() handles zeroing. Hugetlb surplus pages need special handling because they can be pre-allocated into the pool during mmap (by hugetlb_acct_memory) before any page fault. Pool pages are kept around and may need zeroing long after buddy allocation, so a buddy-level zeroed hint (consumed at allocation time) cannot track their state. Add a bool *zeroed output parameter to alloc_hugetlb_folio() so callers know whether the page needs zeroing. Buddy-allocated pages are always zeroed (zeroed by post_alloc_hook). Pool pages use a new HPG_zeroed flag to track whether the page is known-zero (freshly buddy-allocated, never mapped to userspace). The flag is set in alloc_surplus_hugetlb_folio() after buddy allocation and cleared in free_huge_folio() when a user-mapped page returns to the pool. Callers that do not need zeroing (CoW, migration) pass NULL for zeroed and 0 for gfp. Signed-off-by: Michael S. Tsirkin Assisted-by: Claude:claude-opus-4-6 Assisted-by: cursor-agent:GPT-5.4-xhigh --- fs/hugetlbfs/inode.c | 10 ++++++-- include/linux/hugetlb.h | 8 +++++-- mm/hugetlb.c | 52 ++++++++++++++++++++++++++++++----------- 3 files changed, 53 insertions(+), 17 deletions(-) diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 8b05bec08e04..24e42cb10ade 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -810,14 +810,20 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset, * folios in these areas, we need to consume the reserves * to keep reservation accounting consistent. */ - folio = alloc_hugetlb_folio(&pseudo_vma, addr, false); + { + bool zeroed; + + folio = alloc_hugetlb_folio(&pseudo_vma, addr, false, + __GFP_ZERO, &zeroed); if (IS_ERR(folio)) { mutex_unlock(&hugetlb_fault_mutex_table[hash]); error = PTR_ERR(folio); goto out; } - folio_zero_user(folio, addr); + if (!zeroed) + folio_zero_user(folio, addr); __folio_mark_uptodate(folio); + } error = hugetlb_add_to_page_cache(folio, mapping, index); if (unlikely(error)) { restore_reserve_on_error(h, &pseudo_vma, addr, folio); diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 93418625d3c5..950e1702fbd8 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -599,6 +599,7 @@ enum hugetlb_page_flags { HPG_vmemmap_optimized, HPG_raw_hwp_unreliable, HPG_cma, + HPG_zeroed, __NR_HPAGEFLAGS, }; @@ -659,6 +660,7 @@ HPAGEFLAG(Freed, freed) HPAGEFLAG(VmemmapOptimized, vmemmap_optimized) HPAGEFLAG(RawHwpUnreliable, raw_hwp_unreliable) HPAGEFLAG(Cma, cma) +HPAGEFLAG(Zeroed, zeroed) #ifdef CONFIG_HUGETLB_PAGE @@ -706,7 +708,8 @@ int isolate_or_dissolve_huge_folio(struct folio *folio, struct list_head *list); int replace_free_hugepage_folios(unsigned long start_pfn, unsigned long end_pfn); void wait_for_freed_hugetlb_folios(void); struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, - unsigned long addr, bool cow_from_owner); + unsigned long addr, bool cow_from_owner, + gfp_t gfp, bool *zeroed); struct folio *alloc_hugetlb_folio_nodemask(struct hstate *h, int preferred_nid, nodemask_t *nmask, gfp_t gfp_mask, bool allow_alloc_fallback); @@ -1131,7 +1134,8 @@ static inline void wait_for_freed_hugetlb_folios(void) static inline struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, unsigned long addr, - bool cow_from_owner) + bool cow_from_owner, + gfp_t gfp, bool *zeroed) { return NULL; } diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a999f3ead852..8710366d14b7 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1708,6 +1708,9 @@ void free_huge_folio(struct folio *folio) int nid = folio_nid(folio); struct hugepage_subpool *spool = hugetlb_folio_subpool(folio); bool restore_reserve; + + /* Page was mapped to userspace; no longer known-zero */ + folio_clear_hugetlb_zeroed(folio); unsigned long flags; VM_BUG_ON_FOLIO(folio_ref_count(folio), folio); @@ -2110,6 +2113,10 @@ static struct folio *alloc_surplus_hugetlb_folio(struct hstate *h, if (!folio) return NULL; + /* Mark as known-zero only if __GFP_ZERO was requested */ + if (gfp_mask & __GFP_ZERO) + folio_set_hugetlb_zeroed(folio); + spin_lock_irq(&hugetlb_lock); /* * nr_huge_pages needs to be adjusted within the same lock cycle @@ -2173,11 +2180,11 @@ static struct folio *alloc_migrate_hugetlb_folio(struct hstate *h, gfp_t gfp_mas */ static struct folio *alloc_buddy_hugetlb_folio_with_mpol(struct hstate *h, - struct vm_area_struct *vma, unsigned long addr) + struct vm_area_struct *vma, unsigned long addr, gfp_t gfp) { struct folio *folio = NULL; struct mempolicy *mpol; - gfp_t gfp_mask = htlb_alloc_mask(h); + gfp_t gfp_mask = htlb_alloc_mask(h) | gfp; int nid; nodemask_t *nodemask; @@ -2874,7 +2881,8 @@ typedef enum { * When it's set, the allocation will bypass all vma level reservations. */ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, - unsigned long addr, bool cow_from_owner) + unsigned long addr, bool cow_from_owner, + gfp_t gfp, bool *zeroed) { struct hugepage_subpool *spool = subpool_vma(vma); struct hstate *h = hstate_vma(vma); @@ -2883,7 +2891,9 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, map_chg_state map_chg; int ret, idx; struct hugetlb_cgroup *h_cg = NULL; - gfp_t gfp = htlb_alloc_mask(h) | __GFP_RETRY_MAYFAIL; + bool from_pool; + + gfp |= htlb_alloc_mask(h) | __GFP_RETRY_MAYFAIL; idx = hstate_index(h); @@ -2951,13 +2961,15 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, folio = dequeue_hugetlb_folio_vma(h, vma, addr, gbl_chg); if (!folio) { spin_unlock_irq(&hugetlb_lock); - folio = alloc_buddy_hugetlb_folio_with_mpol(h, vma, addr); + folio = alloc_buddy_hugetlb_folio_with_mpol(h, vma, addr, gfp); if (!folio) goto out_uncharge_cgroup; spin_lock_irq(&hugetlb_lock); list_add(&folio->lru, &h->hugepage_activelist); folio_ref_unfreeze(folio, 1); - /* Fall through */ + from_pool = false; + } else { + from_pool = true; } /* @@ -2980,6 +2992,14 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, spin_unlock_irq(&hugetlb_lock); + if (zeroed) { + if (from_pool) + *zeroed = folio_test_hugetlb_zeroed(folio); + else + *zeroed = true; /* buddy-allocated, zeroed by post_alloc_hook */ + folio_clear_hugetlb_zeroed(folio); + } + hugetlb_set_folio_subpool(folio, spool); if (map_chg != MAP_CHG_ENFORCED) { @@ -4988,7 +5008,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, spin_unlock(src_ptl); spin_unlock(dst_ptl); /* Do not use reserve as it's private owned */ - new_folio = alloc_hugetlb_folio(dst_vma, addr, false); + new_folio = alloc_hugetlb_folio(dst_vma, addr, false, 0, NULL); if (IS_ERR(new_folio)) { folio_put(pte_folio); ret = PTR_ERR(new_folio); @@ -5517,7 +5537,7 @@ static vm_fault_t hugetlb_wp(struct vm_fault *vmf) * be acquired again before returning to the caller, as expected. */ spin_unlock(vmf->ptl); - new_folio = alloc_hugetlb_folio(vma, vmf->address, cow_from_owner); + new_folio = alloc_hugetlb_folio(vma, vmf->address, cow_from_owner, 0, NULL); if (IS_ERR(new_folio)) { /* @@ -5711,7 +5731,7 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping, struct vm_fault *vmf) { u32 hash = hugetlb_fault_mutex_hash(mapping, vmf->pgoff); - bool new_folio, new_anon_folio = false; + bool new_folio, new_anon_folio = false, zeroed; struct vm_area_struct *vma = vmf->vma; struct mm_struct *mm = vma->vm_mm; struct hstate *h = hstate_vma(vma); @@ -5777,7 +5797,8 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping, goto out; } - folio = alloc_hugetlb_folio(vma, vmf->address, false); + folio = alloc_hugetlb_folio(vma, vmf->address, false, + __GFP_ZERO, &zeroed); if (IS_ERR(folio)) { /* * Returning error will result in faulting task being @@ -5797,7 +5818,12 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping, ret = 0; goto out; } - folio_zero_user(folio, vmf->real_address); + /* + * Buddy-allocated pages are zeroed in post_alloc_hook(). + * Pool pages bypass the allocator, zero them here. + */ + if (!zeroed) + folio_zero_user(folio, vmf->real_address); __folio_mark_uptodate(folio); new_folio = true; @@ -6236,7 +6262,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte, goto out; } - folio = alloc_hugetlb_folio(dst_vma, dst_addr, false); + folio = alloc_hugetlb_folio(dst_vma, dst_addr, false, 0, NULL); if (IS_ERR(folio)) { pte_t *actual_pte = hugetlb_walk(dst_vma, dst_addr, PMD_SIZE); if (actual_pte) { @@ -6283,7 +6309,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte, goto out; } - folio = alloc_hugetlb_folio(dst_vma, dst_addr, false); + folio = alloc_hugetlb_folio(dst_vma, dst_addr, false, 0, NULL); if (IS_ERR(folio)) { folio_put(*foliop); ret = -ENOMEM; -- MST