Re: [PATCH v2] page_ext: introduce boot parameter 'early_page_ext'

On 2022-08-24 8:09 UTC, mhocko@suse.com wrote:

On Wed 24-08-22 14:50:58, lizhe.67@bytedance.com wrote:
[...]

quoted

diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h
index fabb2e1e087f..3e081cf8a1ec 100644
--- a/include/linux/page_ext.h
+++ b/include/linux/page_ext.h

@@ -38,19 +38,22 @@ struct page_ext {
 
 extern unsigned long page_ext_size;
 extern void pgdat_page_ext_init(struct pglist_data *pgdat);
+#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
+extern bool early_page_ext_enable(void);
+#endif
 
 #ifdef CONFIG_SPARSEMEM
 static inline void page_ext_init_flatmem(void)
 {
 }
-extern void page_ext_init(void);
+extern void page_ext_init(bool early);
 static inline void page_ext_init_flatmem_late(void)
 {
 }
 #else
 extern void page_ext_init_flatmem(void);
 extern void page_ext_init_flatmem_late(void);
-static inline void page_ext_init(void)
+static inline void page_ext_init(bool early)
 {
 }
 #endif

Why do you need to make it CONFIG_DEFERRED_STRUCT_PAGE_INIT
dependant?

Yes it is unnecessary. Thanks!

[...]

quoted

diff --git a/init/main.c b/init/main.c
index 91642a4e69be..3760c0326525 100644
--- a/init/main.c
+++ b/init/main.c

@@ -849,6 +849,8 @@ static void __init mm_init(void)
 	pgtable_init();
 	debug_objects_mem_init();
 	vmalloc_init();
+	/* Should be run after vmap initialization */
+	page_ext_init(true);

you can just 
if (early_page_ext)
	page_ext_init();

quoted

 	/* Should be run before the first non-init thread is created */
 	init_espfix_bsp();
 	/* Should be run after espfix64 is set up. */

@@ -1606,7 +1608,7 @@ static noinline void __init kernel_init_freeable(void)
 	padata_init();
 	page_alloc_init_late();
 	/* Initialize page ext after all struct pages are initialized. */
-	page_ext_init();
+	page_ext_init(false);

if (!early_page_ext)
	page_ext_init();

I think we can use an inline function instead of 'early_page_ext' here. The
reason is that if CONFIG_PAGE_EXTENSION=n, 'early_page_ext' is undefined.
Thought we can #define early_page_ext as false, it is ugly.

quoted

 
 	do_basic_setup();
 

and without the ifdefery it all becomes much more simple.

Yes it becomes much more simple. Thanks for all your advices! I will take your
advices and send a v3 patch.