gup: Turn fault_in_pages_{readable,writeable} into fault_in_{readable,writeable}

Turn fault_in_pages_{readable,writeable} into versions that return the
number of bytes not faulted in, similar to copy_to_user, instead of
returning a non-zero value when any of the requested pages couldn't be
faulted in.  This supports the existing users that require all pages to
be faulted in as well as new users that are happy if any pages can be
faulted in.

Rename the functions to fault_in_{readable,writeable} to make sure
this change doesn't silently break things.

Neither of these functions is entirely trivial and it doesn't seem
useful to inline them, so move them to mm/gup.c.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

1 files changed, 3 insertions, 54 deletions

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 62db6b0176b9..9fe94f7a4f7e 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -733,61 +733,10 @@ int wait_on_page_private_2_killable(struct page *page);
 extern void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter);
 
 /*
- * Fault everything in given userspace address range in.
+ * Fault in userspace address range.
  */
-static inline int fault_in_pages_writeable(char __user *uaddr, size_t size)
-{
-	char __user *end = uaddr + size - 1;
-
-	if (unlikely(size == 0))
-		return 0;
-
-	if (unlikely(uaddr > end))
-		return -EFAULT;
-	/*
-	 * Writing zeroes into userspace here is OK, because we know that if
-	 * the zero gets there, we'll be overwriting it.
-	 */
-	do {
-		if (unlikely(__put_user(0, uaddr) != 0))
-			return -EFAULT;
-		uaddr += PAGE_SIZE;
-	} while (uaddr <= end);
-
-	/* Check whether the range spilled into the next page. */
-	if (((unsigned long)uaddr & PAGE_MASK) ==
-			((unsigned long)end & PAGE_MASK))
-		return __put_user(0, end);
-
-	return 0;
-}
-
-static inline int fault_in_pages_readable(const char __user *uaddr, size_t size)
-{
-	volatile char c;
-	const char __user *end = uaddr + size - 1;
-
-	if (unlikely(size == 0))
-		return 0;
-
-	if (unlikely(uaddr > end))
-		return -EFAULT;
-
-	do {
-		if (unlikely(__get_user(c, uaddr) != 0))
-			return -EFAULT;
-		uaddr += PAGE_SIZE;
-	} while (uaddr <= end);
-
-	/* Check whether the range spilled into the next page. */
-	if (((unsigned long)uaddr & PAGE_MASK) ==
-			((unsigned long)end & PAGE_MASK)) {
-		return __get_user(c, end);
-	}
-
-	(void)c;
-	return 0;
-}
+size_t fault_in_writeable(char __user *uaddr, size_t size);
+size_t fault_in_readable(const char __user *uaddr, size_t size);
 
 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
 				pgoff_t index, gfp_t gfp_mask);