folio->private != NULL indicates a folio carries private data, replacing PG_private. All PG_private users are converted. Remove PG_private and reserve the space as PG_folio for future use. Unused PG_private functions are removed too. Link: https://lore.kernel.org/20260920-remove-pg_private-v5-17-bb68b6a21869@nvidia.com Signed-off-by: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: David Hildenbrand (Arm) <david@kernel.org> Assisted-by: LLM Cc: Baoquan He <baoquan.he@linux.dev> Cc: Mike Rapoport <rppt@kernel.org> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Pratyush Yadav <pratyush@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org> Cc: Jan Kara <jack@suse.cz> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Dave Young <ruirui.yang@linux.dev> Cc: Shuah Khan <skhan@linuxfoundation.org> Cc: Lorenzo Stoakes <ljs@kernel.org> Cc: "Liam R. Howlett" <liam@infradead.org> Cc: Vlastimil Babka <vbabka@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>