fuse: use get_user_pages_fast()

Replace uses of get_user_pages() with get_user_pages_fast().  It looks
nicer and should be faster in most cases.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

fs/fuse/dev.c

@@ -551,10 +551,7 @@ static int fuse_copy_fill(struct fuse_copy_state *cs)
 		cs->iov++;
 		cs->nr_segs--;
 	}
-	down_read(&current->mm->mmap_sem);
-	err = get_user_pages(current, current->mm, cs->addr, 1, cs->write, 0,
-			     &cs->pg, NULL);
-	up_read(&current->mm->mmap_sem);
+	err = get_user_pages_fast(cs->addr, 1, cs->write, &cs->pg);
 	if (err < 0)
 		return err;
 	BUG_ON(err != 1);

fs/fuse/file.c

@@ -994,10 +994,7 @@ static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,
 	nbytes = min_t(size_t, nbytes, FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT);
 	npages = (nbytes + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	npages = clamp(npages, 1, FUSE_MAX_PAGES_PER_REQ);
-	down_read(&current->mm->mmap_sem);
-	npages = get_user_pages(current, current->mm, user_addr, npages, !write,
-				0, req->pages, NULL);
-	up_read(&current->mm->mmap_sem);
+	npages = get_user_pages_fast(user_addr, npages, !write, req->pages);
 	if (npages < 0)
 		return npages;