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SubjectRe: [PATCH] mm: fix page_owner initializing issue for arm32
Hi Mike,

On Sun, Oct 25, 2020 at 11:42:53PM +0800, Mike Rapoport wrote:
> On Fri, Oct 16, 2020 at 05:14:00PM +0800, 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).
>
> Is anything that requires a memblock allocation FLATMEM?
> Any fundamental reason why wouldn't alloc_pages_exact_nid/vzalloc_node()
> work in this case?
>
> It seems to me that for FLATMEM configuration we can allocate the
> page_ext using alloc_pages() with a fallback to vzalloc_node() and then
> we can unify lot's of page_ext code and entirely drop
> page_ext_init_flatmem().
From comments in codes: "page_ext requires contiguous pages, bigger than
MAX_ORDER unless SPARSEMEM."
The size of page_ext for FLATMEM(which used pgdat) should be much larger than
the size for SPARSEMEM which used section.
>
> > 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:
> > --
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> Forum,
> > a Linux Foundation Collaborative Project
> >
> >
>
> --
> Sincerely yours,
> Mike.
>

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