[PATCH 04/10] mm: replace get_user_pages_locked() write/force parameters with gup_flags

Lorenzo Stoakes
2016-10-13T00:20:14Z

This patch removes the write and force parameters from get_user_pages_locked()
and replaces them with a gup_flags parameter 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>
---
include/linux/mm.h | 2 +-
mm/frame_vector.c | 8 +++++++-
mm/gup.c | 12 +++---------
mm/nommu.c | 5 ++++-
4 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6adc4bc..27ab538 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -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);
diff --git a/mm/frame_vector.c b/mm/frame_vector.c
index 381bb07..81b6749 100644
--- a/mm/frame_vector.c
+++ b/mm/frame_vector.c
@@ -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;
}

diff --git a/mm/gup.c b/mm/gup.c
index cfcb014..7a0d033 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -838,18 +838,12 @@ 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);

diff --git a/mm/nommu.c b/mm/nommu.c
index 7e27add..842cfdd 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -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);
--
2.10.0