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mm: remove write/force parameters from __get_user_pages_unlocked()

Browse source 
This removes the redundant '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 <[email protected]>
Acked-by: Paolo Bonzini <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Lorenzo Stoakes 2016-10-13 01:20:12 +01:00 • committed by Linus Torvalds
commit d4944b0ece
6 changed files with 34 additions and 19 deletions
Download patch file Download diff file Expand all files Collapse all files

17
mm/gup.c
View file

@ -875,17 +875,11 @@ 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(&mm->mmap_sem);
ret = __get_user_pages_locked(tsk, mm, start, nr_pages, pages, NULL,
&locked, false, gup_flags);
@ -915,8 +909,15 @@ 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);

12
mm/nommu.c
View file

@ -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(&mm->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);

7
mm/process_vm_access.c
View file

@ -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 |= FOLL_WRITE;
while (!rc && nr_pages && iov_iter_count(iter)) {
int pages = min(nr_pages, max_pages_per_loop);
size_t bytes;
@ -104,8 +108,7 @@ static int process_vm_rw_single_vec(unsigned long addr,
* current/current->mm
*/
pages = __get_user_pages_unlocked(task, mm, pa, pages,
vm_write, 0, process_pages,
FOLL_REMOTE);
process_pages, flags);
if (pages <= 0)
return -EFAULT;