btrfs: sink get_extent parameter to extent_readpages

There's only one caller that passes btrfs_get_extent.
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -4133,8 +4133,7 @@ int extent_writepages(struct extent_io_tree *tree,
 
 int extent_readpages(struct extent_io_tree *tree,
 		     struct address_space *mapping,
-		     struct list_head *pages, unsigned nr_pages,
-		     get_extent_t get_extent)
+		     struct list_head *pages, unsigned nr_pages)
 {
 	struct bio *bio = NULL;
 	unsigned page_idx;
@@ -4160,13 +4159,13 @@ int extent_readpages(struct extent_io_tree *tree,
 		pagepool[nr++] = page;
 		if (nr < ARRAY_SIZE(pagepool))
 			continue;
-		__extent_readpages(tree, pagepool, nr, get_extent, &em_cached,
-				   &bio, &bio_flags, &prev_em_start);
+		__extent_readpages(tree, pagepool, nr, btrfs_get_extent,
+				&em_cached, &bio, &bio_flags, &prev_em_start);
 		nr = 0;
 	}
 	if (nr)
-		__extent_readpages(tree, pagepool, nr, get_extent, &em_cached,
-				   &bio, &bio_flags, &prev_em_start);
+		__extent_readpages(tree, pagepool, nr, btrfs_get_extent,
+				&em_cached, &bio, &bio_flags, &prev_em_start);
 
 	if (em_cached)
 		free_extent_map(em_cached);

fs/btrfs/extent_io.h

@@ -414,8 +414,7 @@ int btree_write_cache_pages(struct address_space *mapping,
 			    struct writeback_control *wbc);
 int extent_readpages(struct extent_io_tree *tree,
 		     struct address_space *mapping,
-		     struct list_head *pages, unsigned nr_pages,
-		     get_extent_t get_extent);
+		     struct list_head *pages, unsigned nr_pages);
 int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		__u64 start, __u64 len);
 void set_page_extent_mapped(struct page *page);

fs/btrfs/inode.c

@@ -8911,8 +8911,7 @@ btrfs_readpages(struct file *file, struct address_space *mapping,
 {
 	struct extent_io_tree *tree;
 	tree = &BTRFS_I(mapping->host)->io_tree;
-	return extent_readpages(tree, mapping, pages, nr_pages,
-				btrfs_get_extent);
+	return extent_readpages(tree, mapping, pages, nr_pages);
 }
 static int __btrfs_releasepage(struct page *page, gfp_t gfp_flags)
 {