linux-kernel - [PATCH 21/40] mm/page_ext: enable early_page_ext when CONFIG_MEM_ALLOC_PROFILING

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Message-ID: <20230501165450.15352-22-surenb@google.com>
Date:   Mon,  1 May 2023 09:54:31 -0700
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     akpm@...ux-foundation.org
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Subject: [PATCH 21/40] mm/page_ext: enable early_page_ext when CONFIG_MEM_ALLOC_PROFILING_DEBUG=y

For all page allocations to be tagged, page_ext has to be initialized
before the first page allocation. Early tasks allocate their stacks
using page allocator before alloc_node_page_ext() initializes page_ext
area, unless early_page_ext is enabled. Therefore these allocations will
generate a warning when CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled.
Enable early_page_ext whenever CONFIG_MEM_ALLOC_PROFILING_DEBUG=y to
ensure page_ext initialization prior to any page allocation. This will
have all the negative effects associated with early_page_ext, such as
possible longer boot time, therefore we enable it only when debugging
with CONFIG_MEM_ALLOC_PROFILING_DEBUG enabled and not universally for
CONFIG_MEM_ALLOC_PROFILING.

Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
---
 mm/page_ext.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/mm/page_ext.c b/mm/page_ext.c
index eaf054ec276c..55ba797f8881 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -96,7 +96,16 @@ unsigned long page_ext_size;
 static unsigned long total_usage;
 struct page_ext *lookup_page_ext(const struct page *page);
 
+#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
+/*
+ * To ensure correct allocation tagging for pages, page_ext should be available
+ * before the first page allocation. Otherwise early task stacks will be
+ * allocated before page_ext initialization and missing tags will be flagged.
+ */
+bool early_page_ext __meminitdata = true;
+#else
 bool early_page_ext __meminitdata;
+#endif
 static int __init setup_early_page_ext(char *str)
 {
 	early_page_ext = true;
-- 
2.40.1.495.gc816e09b53d-goog