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mm: replace get_user_pages_locked() write/force parameters with gup_f…

…lags

This removes the 'write' and 'force' use from get_user_pages_locked()
and replaces them with 'gup_flags' 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 <lstoakes@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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lorenzo-stoakes authored and torvalds committed Oct 13, 2016
1 parent c164154 commit 3b913179c3fa89dd0e304193fa0c746fc0481447
Showing with 15 additions and 12 deletions.
  1. +1 −1 include/linux/mm.h
  2. +7 −1 mm/frame_vector.c
  3. +3 −9 mm/gup.c
  4. +4 −1 mm/nommu.c
@@ -1282,7 +1282,7 @@ long get_user_pages(unsigned long start, unsigned long nr_pages,
int write, int force, struct page **pages,
struct vm_area_struct **vmas);
long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
int write, int force, struct page **pages, int *locked);
unsigned int gup_flags, 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,
struct page **pages, unsigned int gup_flags);
@@ -41,10 +41,16 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
int ret = 0;
int err;
int locked;
unsigned int gup_flags = 0;

if (nr_frames == 0)
return 0;

if (write)
gup_flags |= FOLL_WRITE;
if (force)
gup_flags |= FOLL_FORCE;

if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
nr_frames = vec->nr_allocated;

@@ -59,7 +65,7 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
vec->got_ref = true;
vec->is_pfns = false;
ret = get_user_pages_locked(start, nr_frames,
write, force, (struct page **)(vec->ptrs), &locked);
gup_flags, (struct page **)(vec->ptrs), &locked);
goto out;
}

@@ -848,18 +848,12 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
* up_read(&mm->mmap_sem);
*/
long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
int write, int force, struct page **pages,
unsigned int gup_flags, struct page **pages,
int *locked)
{
unsigned int flags = FOLL_TOUCH;

if (write)
flags |= FOLL_WRITE;
if (force)
flags |= FOLL_FORCE;

return __get_user_pages_locked(current, current->mm, start, nr_pages,
pages, NULL, locked, true, flags);
pages, NULL, locked, true,
gup_flags | FOLL_TOUCH);
}
EXPORT_SYMBOL(get_user_pages_locked);

@@ -176,9 +176,12 @@ long get_user_pages(unsigned long start, unsigned long nr_pages,
EXPORT_SYMBOL(get_user_pages);

long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
int write, int force, struct page **pages,
unsigned int gup_flags, struct page **pages,
int *locked)
{
int write = gup_flags & FOLL_WRITE;
int force = gup_flags & FOLL_FORCE;

return get_user_pages(start, nr_pages, write, force, pages, NULL);
}
EXPORT_SYMBOL(get_user_pages_locked);

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