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From:   Zhenhua Huang <zhenhuah@codeaurora.org>
To:     akpm@linux-foundation.org
Cc:     Zhenhua Huang <zhenhuah@codeaurora.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH] mm: fix page_owner initializing issue for arm32
Date:   Fri, 16 Oct 2020 17:14:00 +0800
Message-Id: <1602839640-13125-1-git-send-email-zhenhuah@codeaurora.org>
Precedence: bulk

Page owner of pages used by page owner itself used is missing on arm32 targets.
The reason is dummy_handle and failure_handle is not initialized correctly.
Buddy allocator is used to initialize these two handles. However, buddy
allocator is not ready when page owner calls it. This change fixed that by
initializing page owner after buddy initialization.

The working flow before and after this change are:
original logic:
1. allocated memory for page_ext(using memblock).
2. invoke the init callback of page_ext_ops like
page_owner(using buddy allocator).
3. initialize buddy.

after this change:
1. allocated memory for page_ext(using memblock).
2. initialize buddy.
3. invoke the init callback of page_ext_ops like
page_owner(using buddy allocator).

with the change, failure/dummy_handle can get its correct value and
page owner output for example has the one for page owner itself:
Page allocated via order 2, mask 0x6202c0(GFP_USER|__GFP_NOWARN), pid 1006, ts
67278156558 ns
PFN 543776 type Unmovable Block 531 type Unmovable Flags 0x0()
 init_page_owner+0x28/0x2f8
 invoke_init_callbacks_flatmem+0x24/0x34
 start_kernel+0x33c/0x5d8
   (null)

Signed-off-by: Zhenhua Huang <zhenhuah@codeaurora.org>
---
 include/linux/page_ext.h | 8 ++++++++
 init/main.c              | 2 ++
 mm/page_ext.c            | 8 +++++++-
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h
index cfce186..aff81ba 100644
--- a/include/linux/page_ext.h
+++ b/include/linux/page_ext.h
@@ -44,8 +44,12 @@ static inline void page_ext_init_flatmem(void)
 {
 }
 extern void page_ext_init(void);
+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)
 {
 }
@@ -76,6 +80,10 @@ static inline void page_ext_init(void)
 {
 }
 
+static inline void page_ext_init_flatmem_late(void)
+{
+}
+
 static inline void page_ext_init_flatmem(void)
 {
 }
diff --git a/init/main.c b/init/main.c
index 130376e..b34c475 100644
--- a/init/main.c
+++ b/init/main.c
@@ -818,6 +818,8 @@ static void __init mm_init(void)
 	init_debug_pagealloc();
 	report_meminit();
 	mem_init();
+	/* page_owner must be initialized after buddy is ready */
+	page_ext_init_flatmem_late();
 	kmem_cache_init();
 	kmemleak_init();
 	pgtable_init();
diff --git a/mm/page_ext.c b/mm/page_ext.c
index a3616f7..373f7a1 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -99,6 +99,13 @@ static void __init invoke_init_callbacks(void)
 	}
 }
 
+#if !defined(CONFIG_SPARSEMEM)
+void __init page_ext_init_flatmem_late(void)
+{
+	invoke_init_callbacks();
+}
+#endif
+
 static inline struct page_ext *get_entry(void *base, unsigned long index)
 {
 	return base + page_ext_size * index;
@@ -177,7 +184,6 @@ void __init page_ext_init_flatmem(void)
 			goto fail;
 	}
 	pr_info("allocated %ld bytes of page_ext\n", total_usage);
-	invoke_init_callbacks();
 	return;
 
 fail:
-- 
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