The quilt patch titled Subject: mm: avoid zeroing user movable page twice with init_on_alloc=1 has been removed from the -mm tree. Its filename was mm-avoid-zeroing-user-movable-page-twice-with-init_on_alloc=1.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Zi Yan <ziy@xxxxxxxxxx> Subject: mm: avoid zeroing user movable page twice with init_on_alloc=1 Date: Fri, 11 Oct 2024 11:03:04 -0400 Commit 6471384af2a6 ("mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options") forces allocated page to be zeroed in post_alloc_hook() when init_on_alloc=1. For order-0 folios, if arch does not define vma_alloc_zeroed_movable_folio(), the default implementation again zeros the page return from the buddy allocator. So the page is zeroed twice. Fix it by passing __GFP_ZERO instead to avoid double page zeroing. At the moment, s390,arm64,x86,alpha,m68k are not impacted since they define their own vma_alloc_zeroed_movable_folio(). For >0 order folios (mTHP and PMD THP), folio_zero_user() is called to zero the folio again. Fix it by calling folio_zero_user() only if init_on_alloc is set. All arch are impacted. Add alloc_zeroed() helper to encapsulate the init_on_alloc check. [ziy@xxxxxxxxxx: comment fixes, per David] Link: https://lkml.kernel.org/r/97DB52E1-C594-49B5-9736-89AC302FAB01@xxxxxxxxxx Link: https://lkml.kernel.org/r/20241011150304.709590-1-ziy@xxxxxxxxxx Signed-off-by: Zi Yan <ziy@xxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> Acked-by: David Hildenbrand <david@xxxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: "Huang, Ying" <ying.huang@xxxxxxxxx> Cc: John Hubbard <jhubbard@xxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx> Cc: Ryan Roberts <ryan.roberts@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/highmem.h | 8 +------- mm/huge_memory.c | 8 +++++++- mm/internal.h | 6 ++++++ mm/memory.c | 10 +++++++++- 4 files changed, 23 insertions(+), 9 deletions(-) --- a/include/linux/highmem.h~mm-avoid-zeroing-user-movable-page-twice-with-init_on_alloc=1 +++ a/include/linux/highmem.h @@ -224,13 +224,7 @@ static inline struct folio *vma_alloc_zeroed_movable_folio(struct vm_area_struct *vma, unsigned long vaddr) { - struct folio *folio; - - folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vaddr); - if (folio) - clear_user_highpage(&folio->page, vaddr); - - return folio; + return vma_alloc_folio(GFP_HIGHUSER_MOVABLE | __GFP_ZERO, 0, vma, vaddr); } #endif --- a/mm/huge_memory.c~mm-avoid-zeroing-user-movable-page-twice-with-init_on_alloc=1 +++ a/mm/huge_memory.c @@ -1165,7 +1165,13 @@ static struct folio *vma_alloc_anon_foli } folio_throttle_swaprate(folio, gfp); - folio_zero_user(folio, addr); + /* + * When a folio is not zeroed during allocation (__GFP_ZERO not used), + * folio_zero_user() is used to make sure that the page corresponding + * to the faulting address will be hot in the cache after zeroing. + */ + if (!alloc_zeroed()) + folio_zero_user(folio, addr); /* * The memory barrier inside __folio_mark_uptodate makes sure that * folio_zero_user writes become visible before the set_pmd_at() --- a/mm/internal.h~mm-avoid-zeroing-user-movable-page-twice-with-init_on_alloc=1 +++ a/mm/internal.h @@ -1276,6 +1276,12 @@ void touch_pud(struct vm_area_struct *vm void touch_pmd(struct vm_area_struct *vma, unsigned long addr, pmd_t *pmd, bool write); +static inline bool alloc_zeroed(void) +{ + return static_branch_maybe(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, + &init_on_alloc); +} + enum { /* mark page accessed */ FOLL_TOUCH = 1 << 16, --- a/mm/memory.c~mm-avoid-zeroing-user-movable-page-twice-with-init_on_alloc=1 +++ a/mm/memory.c @@ -4719,7 +4719,15 @@ static struct folio *alloc_anon_folio(st goto next; } folio_throttle_swaprate(folio, gfp); - folio_zero_user(folio, vmf->address); + /* + * When a folio is not zeroed during allocation + * (__GFP_ZERO not used), folio_zero_user() is used + * to make sure that the page corresponding to the + * faulting address will be hot in the cache after + * zeroing. + */ + if (!alloc_zeroed()) + folio_zero_user(folio, vmf->address); return folio; } next: _ Patches currently in -mm which might be from ziy@xxxxxxxxxx are