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Date:   Mon, 19 Oct 2020 18:39:19 +0800
From:   Zhenhua Huang <zhenhuah@...eaurora.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH] mm: fix page_owner initializing issue for arm32

Fri, Oct 16, 2020 at 06:41:04PM +0800, Vlastimil Babka wrote:
> On 10/16/20 11:14 AM, Zhenhua Huang wrote:
> >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)
> 
> register_dummy_stack should also appear in the above. Either one too many is
> skipped in arm32 stack saving, or the noinline is not honoured. Could be
> investigated separately.
> 
yes, it's another issue I need to investigate. Be noted, the printing is from
4.9 kernel and I will look into separately.
> >
> >Signed-off-by: Zhenhua Huang <zhenhuah@...eaurora.org>
> 
> This should be safe, as the sparse variant page_ext_init() runs even later,
> so:
> 
> Acked-by: Vlastimil Babka <vbabka@...e.cz>
> 
> Nit below:
> 
> >---
> >  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)
> 
> #ifndef is more common if you don't need boolean ops on multiple configs
> 
Thanks, I'll do the change in patchset v2
> >+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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