mm: remove write/force parameters from __get_user_pages_locked()

This removes the redundant 'write' and 'force' parameters from
__get_user_pages_locked() 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>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 33 insertions, 14 deletions

diff --git a/mm/gup.c b/mm/gup.c
index 22cc22e7432f..720eb9385204 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -739,7 +739,6 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
                                                 struct mm_struct *mm,
                                                 unsigned long start,
                                                 unsigned long nr_pages,
-                                                int write, int force,
                                                 struct page **pages,
                                                 struct vm_area_struct **vmas,
                                                 int *locked, bool notify_drop,
@@ -757,10 +756,6 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
 
         if (pages)
                 flags |= FOLL_GET;
-        if (write)
-                flags |= FOLL_WRITE;
-        if (force)
-                flags |= FOLL_FORCE;
 
         pages_done = 0;
         lock_dropped = false;
@@ -856,9 +851,15 @@ long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
                            int write, int force, 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,
-                                       write, force, pages, NULL, locked, true,
-                                       FOLL_TOUCH);
+                                       pages, NULL, locked, true, flags);
 }
 EXPORT_SYMBOL(get_user_pages_locked);
 
@@ -879,9 +880,15 @@ __always_inline long __get_user_pages_unlocked(struct task_struct *tsk, struct m
 {
         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, write, force,
-                                      pages, NULL, &locked, false, gup_flags);
+        ret = __get_user_pages_locked(tsk, mm, start, nr_pages, pages, NULL,
+                                      &locked, false, gup_flags);
         if (locked)
                 up_read(&mm->mmap_sem);
         return ret;
@@ -973,9 +980,15 @@ long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
                 int write, int force, struct page **pages,
                 struct vm_area_struct **vmas)
 {
-        return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
-                                       pages, vmas, NULL, false,
-                                       FOLL_TOUCH | FOLL_REMOTE);
+        unsigned int flags = FOLL_TOUCH | FOLL_REMOTE;
+
+        if (write)
+                flags |= FOLL_WRITE;
+        if (force)
+                flags |= FOLL_FORCE;
+
+        return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
+                                       NULL, false, flags);
 }
 EXPORT_SYMBOL(get_user_pages_remote);
 
@@ -989,9 +1002,15 @@ long get_user_pages(unsigned long start, unsigned long nr_pages,
                 int write, int force, struct page **pages,
                 struct vm_area_struct **vmas)
 {
+        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,
-                                       write, force, pages, vmas, NULL, false,
-                                       FOLL_TOUCH);
+                                       pages, vmas, NULL, false, flags);
 }
 EXPORT_SYMBOL(get_user_pages);