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

Add convenience helpers to get a fs_info from a page or folio pointer
instead of open coding the chain or using btrfs_sb() that in some cases
does one more pointer hop.  This is implemented as a macro (still with
type checking) so we don't need full definitions of struct page, folio,
btrfs_root and btrfs_fs_info. The latter can't be static inlines as this
would create loop between ctree.h <-> fs.h, or the headers would have to
be restructured.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h
index d9a829015274..60ec557a7e3a 100644
--- a/fs/btrfs/fs.h
+++ b/fs/btrfs/fs.h
@@ -836,6 +836,9 @@ struct btrfs_fs_info {
 #define folio_to_inode(_folio)	(BTRFS_I(_Generic((_folio),			\
 					  struct folio *: (_folio))->mapping->host))
 
+#define page_to_fs_info(_page)	 (page_to_inode(_page)->root->fs_info)
+#define folio_to_fs_info(_folio) (folio_to_inode(_folio)->root->fs_info)
+
 static inline u64 btrfs_get_fs_generation(const struct btrfs_fs_info *fs_info)
 {
 	return READ_ONCE(fs_info->generation);