page_ext: introduce boot parameter 'early_page_ext'

In commit 2f1ee0913ce5 ("Revert "mm: use early_pfn_to_nid in
page_ext_init""), we call page_ext_init() after page_alloc_init_late() to
avoid some panic problem.  It seems that we cannot track early page
allocations in current kernel even if page structure has been initialized
early.

This patch introduces a new boot parameter 'early_page_ext' to resolve
this problem.  If we pass it to the kernel, page_ext_init() will be moved
up and the feature 'deferred initialization of struct pages' will be
disabled to initialize the page allocator early and prevent the panic
problem above.  It can help us to catch early page allocations.  This is
useful especially when we find that the free memory value is not the same
right after different kernel booting.

[akpm@linux-foundation.org: fix section issue by removing __meminitdata]
Link: https://lkml.kernel.org/r/20220825102714.669-1-lizhe.67@bytedance.com
Signed-off-by: Li Zhe <lizhe.67@bytedance.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/mm/page_ext.c b/mm/page_ext.c
index b236bdd59fa8..affe80243b6d 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -91,6 +91,14 @@ unsigned long page_ext_size = sizeof(struct page_ext);
 static unsigned long total_usage;
 static struct page_ext *lookup_page_ext(const struct page *page);
 
+bool early_page_ext;
+static int __init setup_early_page_ext(char *str)
+{
+	early_page_ext = true;
+	return 0;
+}
+early_param("early_page_ext", setup_early_page_ext);
+
 static bool __init invoke_need_callbacks(void)
 {
 	int i;