On Wed, Mar 31, 2021 at 07:47:10PM +0100, Matthew Wilcox (Oracle) wrote: > Add folio_private() and set_folio_private() which mirror page_private() > and set_page_private() -- ie folio private data is the same as page > private data. The only difference is that these return a void * > instead of an unsigned long, which matches the majority of users. > > Turn attach_page_private() into attach_folio_private() and reimplement > attach_page_private() as a wrapper. No filesystem which uses page private > data currently supports compound pages, so we're free to define the rules. > attach_page_private() may only be called on a head page; if you want > to add private data to a tail page, you can call set_page_private() > directly (and shouldn't increment the page refcount! That should be > done when adding private data to the head page / folio). > > This saves 597 bytes of text with the distro-derived config that I'm > testing due to removing the calls to compound_head() in get_page() > & put_page(). Except that this seems to be the first patch that uses a field in the non-struct page union leg in struct folio, which could be trivially avoided this looks good: Reviewed-by: Christoph Hellwig <hch@xxxxxx>
