On Fri, May 14, 2021 at 3:01 AM Matthew Wilcox [off-list ref] wrote:

On Thu, May 13, 2021 at 06:58:42PM +0200, Matteo Croce wrote:

quoted

              struct {        /* page_pool used by netstack */
+                     /**
+                      * @pp_magic: magic value to avoid recycling non
+                      * page_pool allocated pages.
+                      * It aliases with page->lru.next

I'm not really keen on documenting what aliases with what.
pp_magic also aliases with compound_head, 'next' (for slab),
and dev_pagemap.  This is an O(n^2) documentation problem ...

Eric asked to document what page->signature aliases, so I did it in
the commit message and in a comment.
I can drop the code comment and leave it just the commit message.

I feel like I want to document the pfmemalloc bit in mm_types.h,
but I don't have a concrete suggestion yet.

quoted

+++ b/include/net/page_pool.h

@@ -63,6 +63,8 @@
  */
 #define PP_ALLOC_CACHE_SIZE  128
 #define PP_ALLOC_CACHE_REFILL        64
+#define PP_SIGNATURE         (POISON_POINTER_DELTA + 0x40)

I wonder if this wouldn't be better in linux/poison.h?

I was thinking the same, I'll do it in the v6.

Regards,
-- 
per aspera ad upstream