Add a gfp_t parameter to alloc_hugetlb_folio(). When __GFP_ZERO is set, the function guarantees the returned folio is zeroed: - Fresh allocations (buddy or gigantic): zeroed by post_alloc_hook via __GFP_ZERO. - Pool pages with HPG_zeroed set: already zeroed, skip. - Pool pages without HPG_zeroed: zeroed via folio_zero_user().
The address parameter is renamed to user_addr; the function aligns it internally for reservation and NUMA policy lookups. For pool pages that need zeroing, user_addr is passed to folio_zero_user() for cache-friendly zeroing near the faulting subpage. All callers pass a page-aligned address; the hugetlb_no_page caller passes vmf->real_address & PAGE_MASK for consistency. HPG_zeroed (stored in hugetlb folio->private bits) tracks known-zero pool pages. It is set when alloc_surplus_hugetlb_folio allocates with __GFP_ZERO, and cleared in free_huge_folio when the page returns to the pool after userspace use. Suggested-by: Gregory Price <[email protected]> Signed-off-by: Michael S. Tsirkin <[email protected]> Assisted-by: Claude:claude-opus-4-6 Assisted-by: cursor-agent:GPT-5.4-xhigh --- fs/hugetlbfs/inode.c | 3 +-- include/linux/hugetlb.h | 5 ++++- mm/hugetlb.c | 47 ++++++++++++++++++++++++++++++----------- 3 files changed, 40 insertions(+), 15 deletions(-) diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 8b05bec08e04..5856a3530c7b 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -810,13 +810,12 @@ 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); + folio = alloc_hugetlb_folio(&pseudo_vma, addr, false, __GFP_ZERO); if (IS_ERR(folio)) { mutex_unlock(&hugetlb_fault_mutex_table[hash]); error = PTR_ERR(folio); goto out; } - folio_zero_user(folio, addr); __folio_mark_uptodate(folio); error = hugetlb_add_to_page_cache(folio, mapping, index); if (unlikely(error)) { diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index f016bc2e8936..49e5557d6cc0 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 user_addr, bool cow_from_owner, + gfp_t gfp); struct folio *alloc_hugetlb_folio_nodemask(struct hstate *h, int preferred_nid, nodemask_t *nmask, gfp_t gfp_mask, bool allow_alloc_fallback); diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a999f3ead852..2ea078d4e5a8 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; @@ -2874,16 +2881,20 @@ 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 user_addr, bool cow_from_owner, + gfp_t gfp) { struct hugepage_subpool *spool = subpool_vma(vma); struct hstate *h = hstate_vma(vma); + unsigned long addr = user_addr & huge_page_mask(h); struct folio *folio; long retval, gbl_chg, gbl_reserve; 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 +2962,15 @@ 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, user_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 +2993,11 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, spin_unlock_irq(&hugetlb_lock); + if ((gfp & __GFP_ZERO) && from_pool && + !folio_test_hugetlb_zeroed(folio)) + folio_zero_user(folio, user_addr); + folio_clear_hugetlb_zeroed(folio); + hugetlb_set_folio_subpool(folio, spool); if (map_chg != MAP_CHG_ENFORCED) { @@ -4988,7 +5006,7 @@ 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); if (IS_ERR(new_folio)) { folio_put(pte_folio); ret = PTR_ERR(new_folio); @@ -5517,7 +5535,7 @@ 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); if (IS_ERR(new_folio)) { /* @@ -5777,7 +5795,13 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping, goto out; } - folio = alloc_hugetlb_folio(vma, vmf->address, false); + /* + * Passing vmf->real_address would work just as well, + * but PAGE_MASK helps make sure we never pass + * USER_ADDR_NONE by mistake. + */ + folio = alloc_hugetlb_folio(vma, vmf->real_address & PAGE_MASK, + false, __GFP_ZERO); if (IS_ERR(folio)) { /* * Returning error will result in faulting task being @@ -5797,7 +5821,6 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping, ret = 0; goto out; } - folio_zero_user(folio, vmf->real_address); __folio_mark_uptodate(folio); new_folio = true; @@ -6236,7 +6259,7 @@ 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); if (IS_ERR(folio)) { pte_t *actual_pte = hugetlb_walk(dst_vma, dst_addr, PMD_SIZE); if (actual_pte) { @@ -6283,7 +6306,7 @@ 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); if (IS_ERR(folio)) { folio_put(*foliop); ret = -ENOMEM; -- MST
