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Re: [PATCH 3/3] page-flags: rectify forward declaration

From Andrew Morton <akpm@linux-foundation.org>
Newsgroups linux.kernel
Subject Re: [PATCH 3/3] page-flags: rectify forward declaration
Date 2015-09-22 00:40 +0200
Message-ID <qbhUB-3qy-7@gated-at.bofh.it> (permalink)
References <qatXQ-7P2-7@gated-at.bofh.it> <qatXQ-7P2-17@gated-at.bofh.it>
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On Sat, 19 Sep 2015 22:42:59 +0530 Sudip Mukherjee <sudipm.mukherjee@gmail.com> wrote:

> compound_head is defined as inline in page-flags.h but in the forward
> declaration of compound_head in the same file missed "inline". As a result
> we got plenty of build warnings while building for some architecture
> like avr32. The warning showed as:
> warning: 'compound_head' declared inline after being called.
> warning: previous declaration of 'compound_head' was here
> 
> ...
>
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -227,7 +227,7 @@ static inline int __TestClearPage##uname(struct page *page) { return 0; }
>  struct page;
>  static inline int PageCompound(struct page *page);
>  static inline int PageTail(struct page *page);
> -static struct page *compound_head(struct page *page);
> +static inline struct page *compound_head(struct page *page);
>  
>  __PAGEFLAG(Locked, locked, PF_NO_TAIL)
>  PAGEFLAG(Error, error, PF_NO_COMPOUND) TESTCLEARFLAG(Error, error, PF_NO_COMPOUND)

Yes, that's an error, in -mm due to Kirill's page-flags patches.


The code is effectively doing

static inline XXX foo(...);

static inline YYY bar(...)
{
	foo(...);
}

inline XXX foo(...)
{
	...
}

ie: asking gcc to inline a forward-defined function.  That does work,
but it's unusual and unexpected, and it's a bit unwise to expect the
compiler to do unusual and more difficult things.

Is it fixable?  Can we use the traditional define-before-using structure?

Also, I'm finding that the patch series introduces a pretty large
bisection hole:

include/linux/page-flags.h: In function 'PageYoung':
include/linux/page-flags.h:327: error: implicit declaration of function 'PF_ANY'
include/linux/page-flags.h:327: error: invalid type argument of '->' (have 'int')
include/linux/page-flags.h:327: error: invalid type argument of '->' (have 'int')

which later gets fixed up by
page-flags-rectify-forward-declaration.patch.

Maybe it's time to do a wholesale refactoring of the patchset?
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[PATCH 0/3] fix allmodconfig failure of avr32 Sudip Mukherjee <sudipm.mukherjee@gmail.com> - 2015-09-19 19:20 +0200
  [PATCH 3/3] page-flags: rectify forward declaration Sudip Mukherjee <sudipm.mukherjee@gmail.com> - 2015-09-19 19:20 +0200
    Re: [PATCH 3/3] page-flags: rectify forward declaration Andrew Morton <akpm@linux-foundation.org> - 2015-09-22 00:40 +0200
      Re: [PATCH 3/3] page-flags: rectify forward declaration Sudip Mukherjee <sudipm.mukherjee@gmail.com> - 2015-09-22 11:00 +0200
        Re: [PATCH 3/3] page-flags: rectify forward declaration Sudip Mukherjee <sudipm.mukherjee@gmail.com> - 2015-09-24 17:30 +0200
      [PATCH 14/16] page-flags: define PG_uptodate behavior on compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
      [PATCH 11/16] page-flags: define PG_swapcache behavior on compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
      [PATCH 02/16] page-flags: move code around "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
      [PATCH 05/16] page-flags: define behavior of FS/IO-related flags on compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
      [PATCH 01/16] page-flags: trivial cleanup for PageTrans* helpers "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
        Re: [PATCH 01/16] page-flags: trivial cleanup for PageTrans*  helpers Christoph Lameter <cl@linux.com> - 2015-09-24 17:50 +0200
      [PATCH 09/16] page-flags: define PG_reserved behavior on compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
      [PATCH 06/16] page-flags: define behavior of LRU-related flags on compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
      [PATCH 13/16] page-flags: define PG_uncached behavior on compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
      [PATCH 10/16] page-flags: define PG_swapbacked behavior on compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
      [PATCH 15/16] page-flags: look at head page if the flag is encoded in page->mapping "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
      [PATCH 08/16] page-flags: define behavior of Xen-related flags on compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
      [PATCH 16/16] mm: sanitize page->mapping for tail pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
        Re: [PATCH 16/16] mm: sanitize page->mapping for tail pages Jerome Glisse <j.glisse@gmail.com> - 2015-09-25 04:30 +0200
      [PATCH 07/16] page-flags: define behavior SL*B-related flags on compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
      [PATCH 00/16] Refreshed page-flags patchset "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
        [PATCH 12/16] page-flags: define PG_mlocked behavior on compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
        [PATCH 03/16] page-flags: introduce page flags policies wrt compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
          Re: [PATCH 03/16] page-flags: introduce page flags policies wrt  compound pages Konstantin Khlebnikov <khlebnikov@yandex-team.ru> - 2015-09-25 14:30 +0200
            Re: [PATCH 03/16] page-flags: introduce page flags policies wrt  compound pages "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-09-25 21:20 +0200
              Re: [PATCH 03/16] page-flags: introduce page flags policies wrt  compound pages "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-09-28 13:10 +0200
                Re: [PATCH 03/16] page-flags: introduce page flags policies wrt  compound pages Konstantin Khlebnikov <khlebnikov@yandex-team.ru> - 2015-09-28 13:50 +0200
                Re: [PATCH 03/16] page-flags: introduce page flags policies wrt  compound pages "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-09-28 20:00 +0200
        [PATCH 04/16] page-flags: define PG_locked behavior on compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
          Re: [PATCH 04/16] page-flags: define PG_locked behavior on compound  pages Christoph Lameter <cl@linux.com> - 2015-09-24 18:10 +0200
            Re: [PATCH 04/16] page-flags: define PG_locked behavior on compound  pages "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-09-24 22:30 +0200
        Re: [PATCH 00/16] Refreshed page-flags patchset Christoph Lameter <cl@linux.com> - 2015-09-24 18:20 +0200
          Re: [PATCH 00/16] Refreshed page-flags patchset "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-09-24 22:30 +0200

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