On Mon, Apr 05, 2021 at 06:13:53PM +0300, Mike Rapoport wrote: > I've also noticed that except page_mapping_file() we have somewhat similar > page_file_mapping(), which seems superfluous, but I didn't dig further to > see how one of them can be dropped. They can't ;-( I looked at it, and they do different things. + * folio_file_mapping - Find the mapping this folio belongs to. + * @folio: The folio. + * + * For folios which are in the page cache, return the mapping that this + * page belongs to. Folios in the swap cache return the mapping of the + * swap file or swap device where the data is stored. This is different + * from the mapping returned by folio_mapping(). The only reason to + * use it is if, like NFS, you return 0 from ->activate_swapfile. page_mapping_file() returns NULL for pages which are in the swap cache, as they no longer need the dcache flushed.
