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SubjectRe: [PATCHv5 01/19] mm/sparsemem: Allocate mem_section at runtime for SPARSEMEM_EXTREME
On Tue, Aug 22, 2017 at 06:28:26PM +0200, Borislav Petkov wrote:
> On Mon, Aug 21, 2017 at 06:28:58PM +0300, Kirill A. Shutemov wrote:
> > Size of mem_section array depends on size of physical address space.
> >
> > In preparation for boot-time switching between paging modes on x86-64
> > we need to make allocation of mem_section dynamic.
> >
> > The patch allocates the array on the first call to
> > sparse_memory_present_with_active_regions().
> >
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > ---
> > include/linux/mmzone.h | 6 +++++-
> > mm/page_alloc.c | 10 ++++++++++
> > mm/sparse.c | 17 +++++++++++------
> > 3 files changed, 26 insertions(+), 7 deletions(-)
>
> This patch needs running through checkpatch:
>
> ERROR: code indent should use tabs where possible
> #53: FILE: include/linux/mmzone.h:1148:
> + if (!mem_section)$
>
> WARNING: please, no spaces at the start of a line
> #53: FILE: include/linux/mmzone.h:1148:
> + if (!mem_section)$
>
> ERROR: code indent should use tabs where possible
> #54: FILE: include/linux/mmzone.h:1149:
> + return NULL;$
>
> WARNING: please, no spaces at the start of a line
> #54: FILE: include/linux/mmzone.h:1149:
> + return NULL;$
>
> ERROR: "foo* bar" should be "foo *bar"
> #99: FILE: mm/sparse.c:106:
> + struct mem_section* root = NULL;
>
> ERROR: do not initialise statics to 0
> #118: FILE: mm/sparse.c:335:
> + static unsigned long old_usemap_snr = 0;
>
> ERROR: do not initialise statics to 0
> #119: FILE: mm/sparse.c:336:
> + static unsigned long old_pgdat_snr = 0;
>
> You should integrate it into your patch creation workflow.

Sorry for this.

> > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> > index fc14b8b3f6ce..9799c2c58ce6 100644
> > --- a/include/linux/mmzone.h
> > +++ b/include/linux/mmzone.h
> > @@ -1137,13 +1137,17 @@ struct mem_section {
> > #define SECTION_ROOT_MASK (SECTIONS_PER_ROOT - 1)
> >
> > #ifdef CONFIG_SPARSEMEM_EXTREME
> > -extern struct mem_section *mem_section[NR_SECTION_ROOTS];
> > +extern struct mem_section **mem_section;
> > #else
> > extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
> > #endif
> >
> > static inline struct mem_section *__nr_to_section(unsigned long nr)
> > {
> > +#ifdef CONFIG_SPARSEMEM_EXTREME
> > + if (!mem_section)
> > + return NULL;
> > +#endif
> > if (!mem_section[SECTION_NR_TO_ROOT(nr)])
> > return NULL;
> > return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 6d30e914afb6..639fd2dce0c4 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -5681,6 +5681,16 @@ void __init sparse_memory_present_with_active_regions(int nid)
> > unsigned long start_pfn, end_pfn;
> > int i, this_nid;
> >
> > +#ifdef CONFIG_SPARSEMEM_EXTREME
> > + if (!mem_section) {
>
> Any chance this ifdeffery and above can use IS_ENABLED() instead?

Unfortunately, no.

This case cannot be changed to IS_ENABLED() as we don't define mem_section
and NR_SECTION_ROOTS for !SPARSEMEM.

The case above cannot be changed as GCC would complain in case of
!SPARSEMEM_EXTREME:

warning: the address of ‘mem_section’ will always evaluate as ‘true’

--
Kirill A. Shutemov

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