| Message ID | 20241011150304.709590-1-ziy@nvidia.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: avoid zeroing user movable page twice with init_on_alloc=1 | expand |
+Vlastimil On 11 Oct 2024, at 11:03, Zi Yan wrote: > 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. > > Added alloc_zeroed() helper to encapsulate the init_on_alloc check. > > Signed-off-by: Zi Yan <ziy@nvidia.com> > --- > include/linux/highmem.h | 8 +------- > mm/huge_memory.c | 3 ++- > mm/internal.h | 6 ++++++ > mm/memory.c | 3 ++- > 4 files changed, 11 insertions(+), 9 deletions(-) > > diff --git a/include/linux/highmem.h b/include/linux/highmem.h > index bec9bd715acf..6e452bd8e7e3 100644 > --- a/include/linux/highmem.h > +++ b/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 > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 82f464865570..5dcbea96edb7 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1176,7 +1176,8 @@ static struct folio *vma_alloc_anon_folio_pmd(struct vm_area_struct *vma, > } > folio_throttle_swaprate(folio, gfp); > > - folio_zero_user(folio, addr); > + 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() > diff --git a/mm/internal.h b/mm/internal.h > index 906da6280c2d..508f7802dd2b 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -1233,6 +1233,12 @@ void touch_pud(struct vm_area_struct *vma, unsigned long addr, > 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, > diff --git a/mm/memory.c b/mm/memory.c > index c67359ddb61a..88252f0e06d0 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -4719,7 +4719,8 @@ static struct folio *alloc_anon_folio(struct vm_fault *vmf) > goto next; > } > folio_throttle_swaprate(folio, gfp); > - folio_zero_user(folio, vmf->address); > + if (!alloc_zeroed()) > + folio_zero_user(folio, vmf->address); > return folio; > } > next: > -- > 2.45.2 Best Regards, Yan, Zi
On 10/11/24 17:03, Zi Yan wrote: > 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. ^ not set? > > Added alloc_zeroed() helper to encapsulate the init_on_alloc check. > > Signed-off-by: Zi Yan <ziy@nvidia.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> > --- > include/linux/highmem.h | 8 +------- > mm/huge_memory.c | 3 ++- > mm/internal.h | 6 ++++++ > mm/memory.c | 3 ++- > 4 files changed, 11 insertions(+), 9 deletions(-) > > diff --git a/include/linux/highmem.h b/include/linux/highmem.h > index bec9bd715acf..6e452bd8e7e3 100644 > --- a/include/linux/highmem.h > +++ b/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 > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 82f464865570..5dcbea96edb7 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1176,7 +1176,8 @@ static struct folio *vma_alloc_anon_folio_pmd(struct vm_area_struct *vma, > } > folio_throttle_swaprate(folio, gfp); > > - folio_zero_user(folio, addr); > + 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() > diff --git a/mm/internal.h b/mm/internal.h > index 906da6280c2d..508f7802dd2b 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -1233,6 +1233,12 @@ void touch_pud(struct vm_area_struct *vma, unsigned long addr, > 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, > diff --git a/mm/memory.c b/mm/memory.c > index c67359ddb61a..88252f0e06d0 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -4719,7 +4719,8 @@ static struct folio *alloc_anon_folio(struct vm_fault *vmf) > goto next; > } > folio_throttle_swaprate(folio, gfp); > - folio_zero_user(folio, vmf->address); > + if (!alloc_zeroed()) > + folio_zero_user(folio, vmf->address); > return folio; > } > next:
On 16 Oct 2024, at 8:53, Vlastimil Babka wrote: > On 10/11/24 17:03, Zi Yan wrote: >> 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. > > ^ not set? You are right. The sentence should be: "Fix it by calling folio_zero_user() only if init_on_alloc is not set." Hi Andrew, Do you want me to resend this with fixed commit log? > >> >> Added alloc_zeroed() helper to encapsulate the init_on_alloc check. >> >> Signed-off-by: Zi Yan <ziy@nvidia.com> > > Acked-by: Vlastimil Babka <vbabka@suse.cz> Thanks. -- Best Regards, Yan, Zi
diff --git a/include/linux/highmem.h b/include/linux/highmem.h index bec9bd715acf..6e452bd8e7e3 100644 --- a/include/linux/highmem.h +++ b/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 diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 82f464865570..5dcbea96edb7 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1176,7 +1176,8 @@ static struct folio *vma_alloc_anon_folio_pmd(struct vm_area_struct *vma, } folio_throttle_swaprate(folio, gfp); - folio_zero_user(folio, addr); + 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() diff --git a/mm/internal.h b/mm/internal.h index 906da6280c2d..508f7802dd2b 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1233,6 +1233,12 @@ void touch_pud(struct vm_area_struct *vma, unsigned long addr, 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, diff --git a/mm/memory.c b/mm/memory.c index c67359ddb61a..88252f0e06d0 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4719,7 +4719,8 @@ static struct folio *alloc_anon_folio(struct vm_fault *vmf) goto next; } folio_throttle_swaprate(folio, gfp); - folio_zero_user(folio, vmf->address); + if (!alloc_zeroed()) + folio_zero_user(folio, vmf->address); return folio; } next:
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. Added alloc_zeroed() helper to encapsulate the init_on_alloc check. Signed-off-by: Zi Yan <ziy@nvidia.com> --- include/linux/highmem.h | 8 +------- mm/huge_memory.c | 3 ++- mm/internal.h | 6 ++++++ mm/memory.c | 3 ++- 4 files changed, 11 insertions(+), 9 deletions(-)