Re: [PATCH 02/10] mm: remove write/force parameters from __get_user_pages_unlocked()

[Jan Kara]

On Thu 13-10-16 01:20:12, Lorenzo Stoakes wrote:
> This patch removes the write and force parameters from
> __get_user_pages_unlocked() to make the use of FOLL_FORCE explicit in callers 
> as
> use of this flag can result in surprising behaviour (and hence bugs) within 
> the
> mm subsystem.
> 
> Signed-off-by: Lorenzo Stoakes 

The patch looks good. You can add:

Reviewed-by: Jan Kara 

Honza
-- 
Jan Kara 
SUSE Labs, CR

Re: [PATCH 02/10] mm: remove write/force parameters from __get_user_pages_unlocked()

[Jan Kara]

On Thu 13-10-16 01:20:12, Lorenzo Stoakes wrote:
> This patch removes the write and force parameters from
> __get_user_pages_unlocked() to make the use of FOLL_FORCE explicit in callers 
> as
> use of this flag can result in surprising behaviour (and hence bugs) within 
> the
> mm subsystem.
> 
> Signed-off-by: Lorenzo Stoakes 

The patch looks good. You can add:

Reviewed-by: Jan Kara 

Honza
-- 
Jan Kara 
SUSE Labs, CR

Re: [PATCH 02/10] mm: remove write/force parameters from __get_user_pages_unlocked()

[Paolo Bonzini]

On 13/10/2016 02:20, Lorenzo Stoakes wrote:
> This patch removes the write and force parameters from
> __get_user_pages_unlocked() to make the use of FOLL_FORCE explicit in callers 
> as
> use of this flag can result in surprising behaviour (and hence bugs) within 
> the
> mm subsystem.
> 
> Signed-off-by: Lorenzo Stoakes 
> ---
>  include/linux/mm.h |  3 +--
>  mm/gup.c   | 17 +
>  mm/nommu.c | 12 +---
>  mm/process_vm_access.c |  7 +--
>  virt/kvm/async_pf.c|  3 ++-
>  virt/kvm/kvm_main.c| 11 ---
>  6 files changed, 34 insertions(+), 19 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index e9caec6..2db98b6 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1285,8 +1285,7 @@ long get_user_pages_locked(unsigned long start, 
> unsigned long nr_pages,
>   int write, int force, struct page **pages, int *locked);
>  long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
>  unsigned long start, unsigned long nr_pages,
> -int write, int force, struct page **pages,
> -unsigned int gup_flags);
> +struct page **pages, unsigned int gup_flags);
>  long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
>   int write, int force, struct page **pages);
>  int get_user_pages_fast(unsigned long start, int nr_pages, int write,
> diff --git a/mm/gup.c b/mm/gup.c
> index ba83942..3d620dd 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -865,17 +865,11 @@ EXPORT_SYMBOL(get_user_pages_locked);
>   */
>  __always_inline long __get_user_pages_unlocked(struct task_struct *tsk, 
> struct mm_struct *mm,
>  unsigned long start, unsigned 
> long nr_pages,
> -int write, int force, struct 
> page **pages,
> -unsigned int gup_flags)
> +struct page **pages, unsigned 
> int gup_flags)
>  {
>   long ret;
>   int locked = 1;
>  
> - if (write)
> - gup_flags |= FOLL_WRITE;
> - if (force)
> - gup_flags |= FOLL_FORCE;
> -
>   down_read(>mmap_sem);
>   ret = __get_user_pages_locked(tsk, mm, start, nr_pages, pages, NULL,
> , false, gup_flags);
> @@ -905,8 +899,15 @@ EXPORT_SYMBOL(__get_user_pages_unlocked);
>  long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
>int write, int force, struct page **pages)
>  {
> + unsigned int flags = FOLL_TOUCH;
> +
> + if (write)
> + flags |= FOLL_WRITE;
> + if (force)
> + flags |= FOLL_FORCE;
> +
>   return __get_user_pages_unlocked(current, current->mm, start, nr_pages,
> -  write, force, pages, FOLL_TOUCH);
> +  pages, flags);
>  }
>  EXPORT_SYMBOL(get_user_pages_unlocked);
>  
> diff --git a/mm/nommu.c b/mm/nommu.c
> index 95daf81..925dcc1 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -185,8 +185,7 @@ EXPORT_SYMBOL(get_user_pages_locked);
>  
>  long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
>  unsigned long start, unsigned long nr_pages,
> -int write, int force, struct page **pages,
> -unsigned int gup_flags)
> +struct page **pages, unsigned int gup_flags)
>  {
>   long ret;
>   down_read(>mmap_sem);
> @@ -200,8 +199,15 @@ EXPORT_SYMBOL(__get_user_pages_unlocked);
>  long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
>int write, int force, struct page **pages)
>  {
> + unsigned int flags = 0;
> +
> + if (write)
> + flags |= FOLL_WRITE;
> + if (force)
> + flags |= FOLL_FORCE;
> +
>   return __get_user_pages_unlocked(current, current->mm, start, nr_pages,
> -  write, force, pages, 0);
> +  pages, flags);
>  }
>  EXPORT_SYMBOL(get_user_pages_unlocked);
>  
> diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
> index 07514d4..be8dc8d 100644
> --- a/mm/process_vm_access.c
> +++ b/mm/process_vm_access.c
> @@ -88,12 +88,16 @@ static int process_vm_rw_single_vec(unsigned long addr,
>   ssize_t rc = 0;
>   unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
>   / sizeof(struct pages *);
> + unsigned int flags = FOLL_REMOTE;
>  
>   /* Work out address and page range required */
>   if (len == 0)
>   return 0;
>   nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;
>  
> + if (vm_write)
> +

Re: [PATCH 02/10] mm: remove write/force parameters from __get_user_pages_unlocked()

[Paolo Bonzini]

On 13/10/2016 02:20, Lorenzo Stoakes wrote:
> This patch removes the write and force parameters from
> __get_user_pages_unlocked() to make the use of FOLL_FORCE explicit in callers 
> as
> use of this flag can result in surprising behaviour (and hence bugs) within 
> the
> mm subsystem.
> 
> Signed-off-by: Lorenzo Stoakes 
> ---
>  include/linux/mm.h |  3 +--
>  mm/gup.c   | 17 +
>  mm/nommu.c | 12 +---
>  mm/process_vm_access.c |  7 +--
>  virt/kvm/async_pf.c|  3 ++-
>  virt/kvm/kvm_main.c| 11 ---
>  6 files changed, 34 insertions(+), 19 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index e9caec6..2db98b6 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1285,8 +1285,7 @@ long get_user_pages_locked(unsigned long start, 
> unsigned long nr_pages,
>   int write, int force, struct page **pages, int *locked);
>  long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
>  unsigned long start, unsigned long nr_pages,
> -int write, int force, struct page **pages,
> -unsigned int gup_flags);
> +struct page **pages, unsigned int gup_flags);
>  long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
>   int write, int force, struct page **pages);
>  int get_user_pages_fast(unsigned long start, int nr_pages, int write,
> diff --git a/mm/gup.c b/mm/gup.c
> index ba83942..3d620dd 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -865,17 +865,11 @@ EXPORT_SYMBOL(get_user_pages_locked);
>   */
>  __always_inline long __get_user_pages_unlocked(struct task_struct *tsk, 
> struct mm_struct *mm,
>  unsigned long start, unsigned 
> long nr_pages,
> -int write, int force, struct 
> page **pages,
> -unsigned int gup_flags)
> +struct page **pages, unsigned 
> int gup_flags)
>  {
>   long ret;
>   int locked = 1;
>  
> - if (write)
> - gup_flags |= FOLL_WRITE;
> - if (force)
> - gup_flags |= FOLL_FORCE;
> -
>   down_read(>mmap_sem);
>   ret = __get_user_pages_locked(tsk, mm, start, nr_pages, pages, NULL,
> , false, gup_flags);
> @@ -905,8 +899,15 @@ EXPORT_SYMBOL(__get_user_pages_unlocked);
>  long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
>int write, int force, struct page **pages)
>  {
> + unsigned int flags = FOLL_TOUCH;
> +
> + if (write)
> + flags |= FOLL_WRITE;
> + if (force)
> + flags |= FOLL_FORCE;
> +
>   return __get_user_pages_unlocked(current, current->mm, start, nr_pages,
> -  write, force, pages, FOLL_TOUCH);
> +  pages, flags);
>  }
>  EXPORT_SYMBOL(get_user_pages_unlocked);
>  
> diff --git a/mm/nommu.c b/mm/nommu.c
> index 95daf81..925dcc1 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -185,8 +185,7 @@ EXPORT_SYMBOL(get_user_pages_locked);
>  
>  long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
>  unsigned long start, unsigned long nr_pages,
> -int write, int force, struct page **pages,
> -unsigned int gup_flags)
> +struct page **pages, unsigned int gup_flags)
>  {
>   long ret;
>   down_read(>mmap_sem);
> @@ -200,8 +199,15 @@ EXPORT_SYMBOL(__get_user_pages_unlocked);
>  long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
>int write, int force, struct page **pages)
>  {
> + unsigned int flags = 0;
> +
> + if (write)
> + flags |= FOLL_WRITE;
> + if (force)
> + flags |= FOLL_FORCE;
> +
>   return __get_user_pages_unlocked(current, current->mm, start, nr_pages,
> -  write, force, pages, 0);
> +  pages, flags);
>  }
>  EXPORT_SYMBOL(get_user_pages_unlocked);
>  
> diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
> index 07514d4..be8dc8d 100644
> --- a/mm/process_vm_access.c
> +++ b/mm/process_vm_access.c
> @@ -88,12 +88,16 @@ static int process_vm_rw_single_vec(unsigned long addr,
>   ssize_t rc = 0;
>   unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
>   / sizeof(struct pages *);
> + unsigned int flags = FOLL_REMOTE;
>  
>   /* Work out address and page range required */
>   if (len == 0)
>   return 0;
>   nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;
>  
> + if (vm_write)
> + flags |=