btrfs: add helpers to get inode from page/folio pointers

Add convenience helpers to get a struct btrfs_inode from a page or folio
pointer instead of open coding the chain or intermediate BTRFS_I. This
is implemented as a macro (still with type checking) so we don't need
full definitions of struct page or address_space.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/disk-io.c

@@ -528,7 +528,8 @@ static void btree_invalidate_folio(struct folio *folio, size_t offset,
 				 size_t length)
 {
 	struct extent_io_tree *tree;
-	tree = &BTRFS_I(folio->mapping->host)->io_tree;
+
+	tree = &folio_to_inode(folio)->io_tree;
 	extent_invalidate_folio(tree, folio, offset);
 	btree_release_folio(folio, GFP_NOFS);
 	if (folio_get_private(folio)) {

fs/btrfs/extent_io.c

@@ -819,7 +819,7 @@ static void submit_extent_page(struct btrfs_bio_ctrl *bio_ctrl,
 			       u64 disk_bytenr, struct page *page,
 			       size_t size, unsigned long pg_offset)
 {
-	struct btrfs_inode *inode = BTRFS_I(page->mapping->host);
+	struct btrfs_inode *inode = page_to_inode(page);
 
 	ASSERT(pg_offset + size <= PAGE_SIZE);
 	ASSERT(bio_ctrl->end_io_func);
@@ -1151,7 +1151,7 @@ static int btrfs_do_readpage(struct page *page, struct extent_map **em_cached,
 int btrfs_read_folio(struct file *file, struct folio *folio)
 {
 	struct page *page = &folio->page;
-	struct btrfs_inode *inode = BTRFS_I(page->mapping->host);
+	struct btrfs_inode *inode = page_to_inode(page);
 	u64 start = page_offset(page);
 	u64 end = start + PAGE_SIZE - 1;
 	struct btrfs_bio_ctrl bio_ctrl = { .opf = REQ_OP_READ };
@@ -1174,7 +1174,7 @@ static inline void contiguous_readpages(struct page *pages[], int nr_pages,
 					struct btrfs_bio_ctrl *bio_ctrl,
 					u64 *prev_em_start)
 {
-	struct btrfs_inode *inode = BTRFS_I(pages[0]->mapping->host);
+	struct btrfs_inode *inode = page_to_inode(pages[0]);
 	int index;
 
 	btrfs_lock_and_flush_ordered_range(inode, start, end, NULL);
@@ -2372,7 +2372,7 @@ int try_release_extent_mapping(struct page *page, gfp_t mask)
 	struct extent_map *em;
 	u64 start = page_offset(page);
 	u64 end = start + PAGE_SIZE - 1;
-	struct btrfs_inode *btrfs_inode = BTRFS_I(page->mapping->host);
+	struct btrfs_inode *btrfs_inode = page_to_inode(page);
 	struct extent_io_tree *tree = &btrfs_inode->io_tree;
 	struct extent_map_tree *map = &btrfs_inode->extent_tree;
 

fs/btrfs/fs.h

@@ -831,6 +831,11 @@ struct btrfs_fs_info {
 #endif
 };
 
+#define page_to_inode(_page)	(BTRFS_I(_Generic((_page),			\
+					  struct page *: (_page))->mapping->host))
+#define folio_to_inode(_folio)	(BTRFS_I(_Generic((_folio),			\
+					  struct folio *: (_folio))->mapping->host))
+
 static inline u64 btrfs_get_fs_generation(const struct btrfs_fs_info *fs_info)
 {
 	return READ_ONCE(fs_info->generation);

fs/btrfs/inode.c

@@ -7971,7 +7971,7 @@ static int btrfs_migrate_folio(struct address_space *mapping,
 static void btrfs_invalidate_folio(struct folio *folio, size_t offset,
 				 size_t length)
 {
-	struct btrfs_inode *inode = BTRFS_I(folio->mapping->host);
+	struct btrfs_inode *inode = folio_to_inode(folio);
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	struct extent_io_tree *tree = &inode->io_tree;
 	struct extent_state *cached_state = NULL;