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(-)
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);
--
2.37.3On 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.
--
Mike Kravetz
> bool shared_pmd = false;
> struct mmu_notifier_range range;
> unsigned long last_addr_mask;
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? -- Thanks, David / dhildenb
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, -- Peter Xu
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. -- Thanks, David / dhildenb
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>
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