Subject: [PATCH 1/8] mm: add rest_of_page() macro

From: Yury Norov <[email-masked]>
Date: Tue, 3 Mar 2026 20:27:09 -0500

The net/9p networking driver has a handy macro to calculate the
amount of bytes from a given pointer to the end of page. Move it
to mm. The following patches apply it tree-wide.

Signed-off-by: Yury Norov <[email-masked]>
---
 include/linux/mm.h    | 2 ++
 net/9p/trans_virtio.c | 6 ------
 2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 5be3d8a8f806..6d1025c6249a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2793,6 +2793,8 @@ extern void pagefault_out_of_memory(void);
 #define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)
 #define offset_in_folio(folio, p) ((unsigned long)(p) & (folio_size(folio) - 1))
 
+#define rest_of_page(p)		(PAGE_SIZE - offset_in_page(p))
+
 /*
  * Parameter block passed down to zap_pte_range in exceptional cases.
  */
diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index 4cdab7094b27..1ca53209d036 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -87,12 +87,6 @@ struct virtio_chan {
 
 static struct list_head virtio_chan_list;
 
-/* How many bytes left in this page. */
-static unsigned int rest_of_page(void *data)
-{
-	return PAGE_SIZE - offset_in_page(data);
-}
-
 /**
  * p9_virtio_close - reclaim resources of a channel
  * @client: client instance
-- 
2.43.0