| Message ID | 20230104225207.1066932-3-peterx@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/uffd: Fix missing markers on hugetlb | expand |
On Wed, Jan 4, 2023 at 10:52 PM Peter Xu <peterx@redhat.com> wrote: > > Switch to use type "long" for page accountings and retval across the whole > procedure of change_protection(). > > The change should have shrinked the possible maximum page number to be half > comparing to previous (ULONG_MAX / 2), but it shouldn't overflow on any > system either because the maximum possible pages touched by change > protection should be ULONG_MAX / PAGE_SIZE. > > Two reasons to switch from "unsigned long" to "long": > > 1. It suites better on count_vm_numa_events(), whose 2nd parameter takes > a long type. > > 2. It paves way for returning negative (error) values in the future. > > Currently the only caller that consumes this retval is change_prot_numa(), > where the unsigned long was converted to an int. Since at it, touching up > the numa code to also take a long, so it'll avoid any possible overflow too > during the int-size convertion. > > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > include/linux/hugetlb.h | 4 ++-- > include/linux/mm.h | 2 +- > mm/hugetlb.c | 4 ++-- > mm/mempolicy.c | 2 +- > mm/mprotect.c | 26 +++++++++++++------------- > 5 files changed, 19 insertions(+), 19 deletions(-) Acked-by: James Houghton <jthoughton@google.com>
On 04.01.23 23:52, Peter Xu wrote: > Switch to use type "long" for page accountings and retval across the whole > procedure of change_protection(). > > The change should have shrinked the possible maximum page number to be half > comparing to previous (ULONG_MAX / 2), but it shouldn't overflow on any > system either because the maximum possible pages touched by change > protection should be ULONG_MAX / PAGE_SIZE. Yeah, highly unlikely. > > Two reasons to switch from "unsigned long" to "long": > > 1. It suites better on count_vm_numa_events(), whose 2nd parameter takes > a long type. > > 2. It paves way for returning negative (error) values in the future. > > Currently the only caller that consumes this retval is change_prot_numa(), > where the unsigned long was converted to an int. Since at it, touching up > the numa code to also take a long, so it'll avoid any possible overflow too > during the int-size convertion. I'm wondering if we should just return the number of changed pages via a separate pointer and later using an int for returning errors -- when touching this interface already. Only who's actually interested in the number of pages would pass a pointer to an unsigned long (NUMA). And code that expects that there never ever are failures (mprotect, NUMA) could simply check for WARN_ON_ONCE(ret). I assume you evaluated that option as well, what was your conclusion?
On 01/04/23 17:52, Peter Xu wrote: > Switch to use type "long" for page accountings and retval across the whole > procedure of change_protection(). > > The change should have shrinked the possible maximum page number to be half > comparing to previous (ULONG_MAX / 2), but it shouldn't overflow on any > system either because the maximum possible pages touched by change > protection should be ULONG_MAX / PAGE_SIZE. > > Two reasons to switch from "unsigned long" to "long": > > 1. It suites better on count_vm_numa_events(), whose 2nd parameter takes > a long type. > > 2. It paves way for returning negative (error) values in the future. > > Currently the only caller that consumes this retval is change_prot_numa(), > where the unsigned long was converted to an int. Since at it, touching up > the numa code to also take a long, so it'll avoid any possible overflow too > during the int-size convertion. > > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > include/linux/hugetlb.h | 4 ++-- > include/linux/mm.h | 2 +- > mm/hugetlb.c | 4 ++-- > mm/mempolicy.c | 2 +- > mm/mprotect.c | 26 +++++++++++++------------- > 5 files changed, 19 insertions(+), 19 deletions(-) Acked-by: Mike Kravetz <mike.kravetz@oracle.com> > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index b6b10101bea7..e3aa336df900 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -248,7 +248,7 @@ void hugetlb_vma_lock_release(struct kref *kref); > > int pmd_huge(pmd_t pmd); > int pud_huge(pud_t pud); > -unsigned long hugetlb_change_protection(struct vm_area_struct *vma, > +long hugetlb_change_protection(struct vm_area_struct *vma, > unsigned long address, unsigned long end, pgprot_t newprot, > unsigned long cp_flags); > > @@ -437,7 +437,7 @@ static inline void move_hugetlb_state(struct folio *old_folio, > { > } > > -static inline unsigned long hugetlb_change_protection( > +static inline long hugetlb_change_protection( > struct vm_area_struct *vma, unsigned long address, > unsigned long end, pgprot_t newprot, > unsigned long cp_flags) > diff --git a/include/linux/mm.h b/include/linux/mm.h > index c37f9330f14e..86fe17e6ded7 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2132,7 +2132,7 @@ static inline bool vma_wants_manual_pte_write_upgrade(struct vm_area_struct *vma > } > bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, > pte_t pte); > -extern unsigned long change_protection(struct mmu_gather *tlb, > +extern long change_protection(struct mmu_gather *tlb, > struct vm_area_struct *vma, unsigned long start, > unsigned long end, unsigned long cp_flags); > extern int mprotect_fixup(struct mmu_gather *tlb, struct vm_area_struct *vma, > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 017d9159cddf..84bc665c7c86 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -6613,7 +6613,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, > return i ? i : err; > } > > -unsigned long hugetlb_change_protection(struct vm_area_struct *vma, > +long hugetlb_change_protection(struct vm_area_struct *vma, > unsigned long address, unsigned long end, > pgprot_t newprot, unsigned long cp_flags) > { > @@ -6622,7 +6622,7 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, > pte_t *ptep; > pte_t pte; > struct hstate *h = hstate_vma(vma); > - unsigned long pages = 0, psize = huge_page_size(h); > + long pages = 0, psize = huge_page_size(h); Small nit, psize is passed to routines as an unsigned long argument. Arithmetic should always be correct, but I am not sure if some of the static checkers may complain.
On Thu, Jan 05, 2023 at 09:44:16AM +0100, David Hildenbrand wrote: > I'm wondering if we should just return the number of changed pages via a > separate pointer and later using an int for returning errors -- when > touching this interface already. > > Only who's actually interested in the number of pages would pass a pointer > to an unsigned long (NUMA). > > And code that expects that there never ever are failures (mprotect, NUMA) > could simply check for WARN_ON_ONCE(ret). > > I assume you evaluated that option as well, what was your conclusion? Since a single long can cover both things as retval, it's better to keep it simple? Thanks,
On 05.01.23 20:22, Peter Xu wrote: > On Thu, Jan 05, 2023 at 09:44:16AM +0100, David Hildenbrand wrote: >> I'm wondering if we should just return the number of changed pages via a >> separate pointer and later using an int for returning errors -- when >> touching this interface already. >> >> Only who's actually interested in the number of pages would pass a pointer >> to an unsigned long (NUMA). >> >> And code that expects that there never ever are failures (mprotect, NUMA) >> could simply check for WARN_ON_ONCE(ret). >> >> I assume you evaluated that option as well, what was your conclusion? > > Since a single long can cover both things as retval, it's better to keep it > simple? Thanks, > Fine with me.
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index b6b10101bea7..e3aa336df900 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -248,7 +248,7 @@ void hugetlb_vma_lock_release(struct kref *kref); int pmd_huge(pmd_t pmd); int pud_huge(pud_t pud); -unsigned long hugetlb_change_protection(struct vm_area_struct *vma, +long hugetlb_change_protection(struct vm_area_struct *vma, unsigned long address, unsigned long end, pgprot_t newprot, unsigned long cp_flags); @@ -437,7 +437,7 @@ static inline void move_hugetlb_state(struct folio *old_folio, { } -static inline unsigned long hugetlb_change_protection( +static inline long hugetlb_change_protection( struct vm_area_struct *vma, unsigned long address, unsigned long end, pgprot_t newprot, unsigned long cp_flags) diff --git a/include/linux/mm.h b/include/linux/mm.h index c37f9330f14e..86fe17e6ded7 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2132,7 +2132,7 @@ static inline bool vma_wants_manual_pte_write_upgrade(struct vm_area_struct *vma } bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, pte_t pte); -extern unsigned long change_protection(struct mmu_gather *tlb, +extern long change_protection(struct mmu_gather *tlb, struct vm_area_struct *vma, unsigned long start, unsigned long end, unsigned long cp_flags); extern int mprotect_fixup(struct mmu_gather *tlb, struct vm_area_struct *vma, diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 017d9159cddf..84bc665c7c86 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6613,7 +6613,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, return i ? i : err; } -unsigned long hugetlb_change_protection(struct vm_area_struct *vma, +long hugetlb_change_protection(struct vm_area_struct *vma, unsigned long address, unsigned long end, pgprot_t newprot, unsigned long cp_flags) { @@ -6622,7 +6622,7 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, pte_t *ptep; pte_t pte; struct hstate *h = hstate_vma(vma); - unsigned long pages = 0, psize = huge_page_size(h); + long pages = 0, psize = huge_page_size(h); bool shared_pmd = false; struct mmu_notifier_range range; unsigned long last_addr_mask; diff --git a/mm/mempolicy.c b/mm/mempolicy.c index d3558248a0f0..a86b8f15e2f0 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -631,7 +631,7 @@ unsigned long change_prot_numa(struct vm_area_struct *vma, unsigned long addr, unsigned long end) { struct mmu_gather tlb; - int nr_updated; + long nr_updated; tlb_gather_mmu(&tlb, vma->vm_mm); diff --git a/mm/mprotect.c b/mm/mprotect.c index 71358e45a742..0af22ab59ea8 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -80,13 +80,13 @@ bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, return pte_dirty(pte); } -static unsigned long change_pte_range(struct mmu_gather *tlb, +static long change_pte_range(struct mmu_gather *tlb, struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr, unsigned long end, pgprot_t newprot, unsigned long cp_flags) { pte_t *pte, oldpte; spinlock_t *ptl; - unsigned long pages = 0; + long pages = 0; int target_node = NUMA_NO_NODE; bool prot_numa = cp_flags & MM_CP_PROT_NUMA; bool uffd_wp = cp_flags & MM_CP_UFFD_WP; @@ -353,13 +353,13 @@ uffd_wp_protect_file(struct vm_area_struct *vma, unsigned long cp_flags) } \ } while (0) -static inline unsigned long change_pmd_range(struct mmu_gather *tlb, +static inline long change_pmd_range(struct mmu_gather *tlb, struct vm_area_struct *vma, pud_t *pud, unsigned long addr, unsigned long end, pgprot_t newprot, unsigned long cp_flags) { pmd_t *pmd; unsigned long next; - unsigned long pages = 0; + long pages = 0; unsigned long nr_huge_updates = 0; struct mmu_notifier_range range; @@ -367,7 +367,7 @@ static inline unsigned long change_pmd_range(struct mmu_gather *tlb, pmd = pmd_offset(pud, addr); do { - unsigned long this_pages; + long this_pages; next = pmd_addr_end(addr, end); @@ -437,13 +437,13 @@ static inline unsigned long change_pmd_range(struct mmu_gather *tlb, return pages; } -static inline unsigned long change_pud_range(struct mmu_gather *tlb, +static inline long change_pud_range(struct mmu_gather *tlb, struct vm_area_struct *vma, p4d_t *p4d, unsigned long addr, unsigned long end, pgprot_t newprot, unsigned long cp_flags) { pud_t *pud; unsigned long next; - unsigned long pages = 0; + long pages = 0; pud = pud_offset(p4d, addr); do { @@ -458,13 +458,13 @@ static inline unsigned long change_pud_range(struct mmu_gather *tlb, return pages; } -static inline unsigned long change_p4d_range(struct mmu_gather *tlb, +static inline long change_p4d_range(struct mmu_gather *tlb, struct vm_area_struct *vma, pgd_t *pgd, unsigned long addr, unsigned long end, pgprot_t newprot, unsigned long cp_flags) { p4d_t *p4d; unsigned long next; - unsigned long pages = 0; + long pages = 0; p4d = p4d_offset(pgd, addr); do { @@ -479,14 +479,14 @@ static inline unsigned long change_p4d_range(struct mmu_gather *tlb, return pages; } -static unsigned long change_protection_range(struct mmu_gather *tlb, +static long change_protection_range(struct mmu_gather *tlb, struct vm_area_struct *vma, unsigned long addr, unsigned long end, pgprot_t newprot, unsigned long cp_flags) { struct mm_struct *mm = vma->vm_mm; pgd_t *pgd; unsigned long next; - unsigned long pages = 0; + long pages = 0; BUG_ON(addr >= end); pgd = pgd_offset(mm, addr); @@ -505,12 +505,12 @@ static unsigned long change_protection_range(struct mmu_gather *tlb, return pages; } -unsigned long change_protection(struct mmu_gather *tlb, +long change_protection(struct mmu_gather *tlb, struct vm_area_struct *vma, unsigned long start, unsigned long end, unsigned long cp_flags) { pgprot_t newprot = vma->vm_page_prot; - unsigned long pages; + long pages; BUG_ON((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL);
Switch to use type "long" for page accountings and retval across the whole procedure of change_protection(). The change should have shrinked the possible maximum page number to be half comparing to previous (ULONG_MAX / 2), but it shouldn't overflow on any system either because the maximum possible pages touched by change protection should be ULONG_MAX / PAGE_SIZE. Two reasons to switch from "unsigned long" to "long": 1. It suites better on count_vm_numa_events(), whose 2nd parameter takes a long type. 2. It paves way for returning negative (error) values in the future. Currently the only caller that consumes this retval is change_prot_numa(), where the unsigned long was converted to an int. Since at it, touching up the numa code to also take a long, so it'll avoid any possible overflow too during the int-size convertion. Signed-off-by: Peter Xu <peterx@redhat.com> --- include/linux/hugetlb.h | 4 ++-- include/linux/mm.h | 2 +- mm/hugetlb.c | 4 ++-- mm/mempolicy.c | 2 +- mm/mprotect.c | 26 +++++++++++++------------- 5 files changed, 19 insertions(+), 19 deletions(-)