[PATCH 6/8] mm/gup: make locked never NULL in the internal GUP functions

[Jason Gunthorpe <jgg@nvidia.com>]

Now that NULL locked doesn't have a special meaning we can just make it
non-NULL in all cases and remove the special tests.

get_user_pages() and pin_user_pages() can safely pass in a locked = 1

get_user_pages_remote) and pin_user_pages_remote() can swap in a local
variable for locked if NULL is passed.

Remove all the NULL checks.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 mm/gup.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 4c360fb05cf3e4..1ccfff759a29eb 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -930,8 +930,8 @@ static int faultin_page(struct vm_area_struct *vma,
 		 * mmap lock in the page fault handler. Sanity check this.
 		 */
 		WARN_ON_ONCE(fault_flags & FAULT_FLAG_RETRY_NOWAIT);
-		if (locked)
-			*locked = 0;
+		*locked = 0;
+
 		/*
 		 * We should do the same as VM_FAULT_RETRY, but let's not
 		 * return -EBUSY since that's not reflecting the reality of
@@ -951,7 +951,7 @@ static int faultin_page(struct vm_area_struct *vma,
 	}
 
 	if (ret & VM_FAULT_RETRY) {
-		if (locked && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
+		if (!(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
 			*locked = 0;
 		return -EBUSY;
 	}
@@ -1121,7 +1121,7 @@ static long __get_user_pages(struct mm_struct *mm,
 				i = follow_hugetlb_page(mm, vma, pages, vmas,
 						&start, &nr_pages, i,
 						gup_flags, locked);
-				if (locked && *locked == 0) {
+				if (!*locked) {
 					/*
 					 * We've got a VM_FAULT_RETRY
 					 * and we've lost mmap_lock.
@@ -1345,7 +1345,7 @@ static __always_inline long __get_user_pages_locked(struct mm_struct *mm,
 	 * The internal caller expects GUP to manage the lock internally and the
 	 * lock must be released when this returns.
 	 */
-	if (locked && !*locked) {
+	if (!*locked) {
 		if (mmap_read_lock_killable(mm))
 			return -EAGAIN;
 		lock_dropped = true;
@@ -1679,7 +1679,7 @@ static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start,
 	 * The internal caller expects GUP to manage the lock internally and the
 	 * lock must be released when this returns.
 	 */
-	if (locked && !*locked) {
+	if (!*locked) {
 		if (mmap_read_lock_killable(mm))
 			return -EAGAIN;
 		must_unlock = true;
@@ -2218,11 +2218,14 @@ long get_user_pages_remote(struct mm_struct *mm,
 		unsigned int gup_flags, struct page **pages,
 		struct vm_area_struct **vmas, int *locked)
 {
+	int local_locked = 1;
+
 	if (!is_valid_gup_args(pages, vmas, locked, &gup_flags,
 			       FOLL_TOUCH | FOLL_REMOTE))
 		return -EINVAL;
 
-	return __get_user_pages_locked(mm, start, nr_pages, pages, vmas, locked,
+	return __get_user_pages_locked(mm, start, nr_pages, pages, vmas,
+				       locked ? locked : &local_locked,
 				       gup_flags);
 }
 EXPORT_SYMBOL(get_user_pages_remote);
@@ -2257,11 +2260,13 @@ long get_user_pages(unsigned long start, unsigned long nr_pages,
 		unsigned int gup_flags, struct page **pages,
 		struct vm_area_struct **vmas)
 {
+	int locked = 1;
+
 	if (!is_valid_gup_args(pages, vmas, NULL, &gup_flags, FOLL_TOUCH))
 		return -EINVAL;
 
 	return __get_user_pages_locked(current->mm, start, nr_pages, pages,
-				       vmas, NULL, gup_flags);
+				       vmas, &locked, gup_flags);
 }
 EXPORT_SYMBOL(get_user_pages);
 
@@ -3154,10 +3159,13 @@ long pin_user_pages_remote(struct mm_struct *mm,
 			   unsigned int gup_flags, struct page **pages,
 			   struct vm_area_struct **vmas, int *locked)
 {
+	int local_locked = 1;
+
 	if (!is_valid_gup_args(pages, vmas, locked, &gup_flags,
 			       FOLL_PIN | FOLL_TOUCH | FOLL_REMOTE))
 		return 0;
-	return __gup_longterm_locked(mm, start, nr_pages, pages, vmas, locked,
+	return __gup_longterm_locked(mm, start, nr_pages, pages, vmas,
+				     locked ? locked : &local_locked,
 				     gup_flags);
 }
 EXPORT_SYMBOL(pin_user_pages_remote);
@@ -3183,10 +3191,12 @@ long pin_user_pages(unsigned long start, unsigned long nr_pages,
 		    unsigned int gup_flags, struct page **pages,
 		    struct vm_area_struct **vmas)
 {
+	int locked = 1;
+
 	if (!is_valid_gup_args(pages, vmas, NULL, &gup_flags, FOLL_PIN))
 		return 0;
 	return __gup_longterm_locked(current->mm, start, nr_pages,
-				     pages, vmas, NULL, gup_flags);
+				     pages, vmas, &locked, gup_flags);
 }
 EXPORT_SYMBOL(pin_user_pages);
 
-- 
2.39.0