On Mon, Feb 14, 2022 at 08:00:11PM +0000, Matthew Wilcox (Oracle) wrote: > folio_mapped() is expensive because it has to check each page's mapcount > field. A cheaper check is whether there are any extra references to > the page, other than the one we own and the ones held by the page cache. > The call to remove_mapping() will fail in any case if it cannot freeze > the refcount, but failing here avoids cycling the i_pages spinlock. I wonder if something like this should also be in a comment near the check in the code.
