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Commit d4944b0e authored by Lorenzo Stoakes's avatar Lorenzo Stoakes Committed by Linus Torvalds
Browse files

mm: remove write/force parameters from __get_user_pages_unlocked() 



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: default avatarLorenzo Stoakes <lstoakes@gmail.com>
Acked-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 859110d7

include/linux/mm.h

+1 −2
Original line number Diff line number Diff line
@@ -1285,8 +1285,7 @@ long get_user_pages_locked(unsigned long start, unsigned long nr_pages, 
		    int write, int force, 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,

			       int write, int force, struct page **pages,

			       unsigned int gup_flags);

			       struct page **pages, unsigned int gup_flags);

long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,

		    int write, int force, struct page **pages);

int get_user_pages_fast(unsigned long start, int nr_pages, int write,

mm/gup.c

+9 −8
Original line number Diff line number Diff line
@@ -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);

mm/nommu.c

+9 −3
Original line number Diff line number Diff line
@@ -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);

mm/process_vm_access.c

+5 −2
Original line number Diff line number Diff line
@@ -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;

virt/kvm/async_pf.c

+2 −1
Original line number Diff line number Diff line
@@ -84,7 +84,8 @@ static void async_pf_execute(struct work_struct *work) 
	 * mm and might be done in another context, so we must

	 * use FOLL_REMOTE.

	 */

	__get_user_pages_unlocked(NULL, mm, addr, 1, 1, 0, NULL, FOLL_REMOTE);

	__get_user_pages_unlocked(NULL, mm, addr, 1, NULL,

			FOLL_WRITE | FOLL_REMOTE);



	kvm_async_page_present_sync(vcpu, apf);