alloc_tag: introduce pgtag_ref_handle to abstract page tag references

To simplify later changes to page tag references, introduce new
pgtag_ref_handle type.  This allows easy replacement of page_ext as a
storage of page allocation tags.

Link: https://lkml.kernel.org/r/20241023170759.999909-6-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Daniel Gomez <da.gomez@samsung.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Minchan Kim <minchan@google.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Petr Pavlu <petr.pavlu@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Sourav Panda <souravpanda@google.com>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas Huth <thuth@redhat.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Xiongwei Song <xiongwei.song@windriver.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 13 insertions, 12 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index eb070c14e309..f9120ac6d901 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4181,37 +4181,38 @@ static inline void pgalloc_tag_split(struct folio *folio, int old_order, int new
 		return;
 
 	for (i = nr_pages; i < (1 << old_order); i += nr_pages) {
-		union codetag_ref *ref = get_page_tag_ref(folio_page(folio, i));
+		union pgtag_ref_handle handle;
+		union codetag_ref ref;
 
-		if (ref) {
+		if (get_page_tag_ref(folio_page(folio, i), &ref, &handle)) {
 			/* Set new reference to point to the original tag */
-			alloc_tag_ref_set(ref, tag);
-			put_page_tag_ref(ref);
+			alloc_tag_ref_set(&ref, tag);
+			update_page_tag_ref(handle, &ref);
+			put_page_tag_ref(handle);
 		}
 	}
 }
 
 static inline void pgalloc_tag_copy(struct folio *new, struct folio *old)
 {
+	union pgtag_ref_handle handle;
+	union codetag_ref ref;
 	struct alloc_tag *tag;
-	union codetag_ref *ref;
 
 	tag = pgalloc_tag_get(&old->page);
 	if (!tag)
 		return;
 
-	ref = get_page_tag_ref(&new->page);
-	if (!ref)
+	if (!get_page_tag_ref(&new->page, &ref, &handle))
 		return;
 
 	/* Clear the old ref to the original allocation tag. */
 	clear_page_tag_ref(&old->page);
 	/* Decrement the counters of the tag on get_new_folio. */
-	alloc_tag_sub(ref, folio_size(new));
-
-	__alloc_tag_ref_set(ref, tag);
-
-	put_page_tag_ref(ref);
+	alloc_tag_sub(&ref, folio_size(new));
+	__alloc_tag_ref_set(&ref, tag);
+	update_page_tag_ref(handle, &ref);
+	put_page_tag_ref(handle);
 }
 #else /* !CONFIG_MEM_ALLOC_PROFILING */
 static inline void pgalloc_tag_split(struct folio *folio, int old_order, int new_order)