linux-kernel - Re: [PATCH] mm: Change return type to vm_fault

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Message-ID: <CAFqt6zbGyDktxBe0t4W-G8bicA4P8-vDm6fOk+kTod7SHoxvZA@mail.gmail.com>
Date:   Sat, 2 Jun 2018 20:25:29 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Al Viro <viro@...iv.linux.org.uk>, Hugh Dickins <hughd@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        zi.yan@...rutgers.edu,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Mark Rutland <mark.rutland@....com>, riel@...hat.com,
        pasha.tatashin@...cle.com, jschoenh@...zon.de,
        Kate Stewart <kstewart@...uxfoundation.org>,
        David Rientjes <rientjes@...gle.com>, tglx@...utronix.de,
        Peter Zijlstra <peterz@...radead.org>,
        Mel Gorman <mgorman@...e.de>, yang.s@...baba-inc.com,
        Minchan Kim <minchan@...nel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-kernel@...r.kernel.org, Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: Change return type to vm_fault_t

On Wed, May 30, 2018 at 4:46 PM, Matthew Wilcox <willy@...radead.org> wrote:
> On Wed, May 30, 2018 at 09:10:47AM +0530, Souptick Joarder wrote:
>> On Tue, May 29, 2018 at 11:04 PM, Matthew Wilcox <willy@...radead.org> wrote:
>> > I see:
>> >
>> > mm/gup.c:817:15: warning: invalid assignment: |=
>> > mm/gup.c:817:15:    left side has type int
>> > mm/gup.c:817:15:    right side has type restricted vm_fault_t
>> >
>> > are you building with 'c=2' or 'C=2'?
>>
>> Building with C=2.
>> Do I need to enable any separate FLAG ?
>
> Nope.  Here's what I have:
>
> willy@...o:~/kernel/souptick$ make C=2 mm/gup.o
>   CHK     include/config/kernel.release
>   CHK     include/generated/uapi/linux/version.h
>   CHK     include/generated/utsrelease.h
>   CHECK   arch/x86/purgatory/purgatory.c
>   CHECK   arch/x86/purgatory/sha256.c
>   CHECK   arch/x86/purgatory/string.c
> arch/x86/purgatory/../boot/string.c:134:6: warning: symbol 'simple_strtol' was not declared. Should it be static?
>   CHK     include/generated/bounds.h
>   CHK     include/generated/timeconst.h
>   CHK     include/generated/asm-offsets.h
>   CALL    scripts/checksyscalls.sh
>   DESCEND  objtool
>   CHECK   scripts/mod/empty.c
>   CHK     scripts/mod/devicetable-offsets.h
>   CHECK   mm/gup.c
> mm/gup.c:817:15: warning: invalid assignment: |=
> mm/gup.c:817:15:    left side has type int
> mm/gup.c:817:15:    right side has type restricted vm_fault_t
>   CC      mm/gup.o
>

Matthew,

Due to some unidentified error still not able to catch this warning
in (X86_64 + sparse) compilation. It is constantly showing below error.

Documents/linux-4.17-rc7$ make C=2 -j4 mm/gup.o

CHK     include/config/kernel.release
  CHK     include/generated/uapi/linux/version.h
  DESCEND  objtool
  CHK     include/generated/utsrelease.h
  CHECK   scripts/mod/empty.c
  CHK     scripts/mod/devicetable-offsets.h
  CHK     include/generated/bounds.h
  CHK     include/generated/timeconst.h
  CHK     include/generated/asm-offsets.h
  CALL    scripts/checksyscalls.sh
  CHECK   mm/gup.c
mm/gup.c:394:17: error: undefined identifier '__COUNTER__'
mm/gup.c:439:9: error: undefined identifier '__COUNTER__'
mm/gup.c:441:9: error: undefined identifier '__COUNTER__'
mm/gup.c:443:9: error: undefined identifier '__COUNTER__'
mm/gup.c:508:17: error: undefined identifier '__COUNTER__'
mm/gup.c:716:25: error: undefined identifier '__COUNTER__'
mm/gup.c:826:17: error: undefined identifier '__COUNTER__'
mm/gup.c:863:17: error: undefined identifier '__COUNTER__'
mm/gup.c:865:17: error: undefined identifier '__COUNTER__'
mm/gup.c:882:25: error: undefined identifier '__COUNTER__'
mm/gup.c:883:25: error: undefined identifier '__COUNTER__'
mm/gup.c:920:25: error: undefined identifier '__COUNTER__'
./include/linux/hugetlb.h:239:9: error: undefined identifier '__COUNTER__'

But able to capture it in (powerpc + sparse) compilation.
I will fix it in v2.

/Documents/linux-4.17-rc7$ make C=2 ARCH=powerpc
CROSS_COMPILE=powerpc-linux-gnu- mm/gup.o

  CHK     include/config/kernel.release
  CHK     include/generated/uapi/linux/version.h
  CHK     include/generated/utsrelease.h
  CHK     include/generated/bounds.h
  CHK     include/generated/timeconst.h
  CHK     include/generated/asm-offsets.h
  CALL    scripts/checksyscalls.sh
  CHECK   scripts/mod/empty.c
  CHK     scripts/mod/devicetable-offsets.h
  CHECK   mm/gup.c
./arch/powerpc/include/asm/book3s/64/pgtable.h:669:24: warning:
restricted __be64 degrades to integer
mm/gup.c:820:15: warning: incorrect type in assignment (different base types)
mm/gup.c:820:15:    expected int [signed] major
mm/gup.c:820:15:    got restricted vm_fault_t
mm/gup.c:1247:24: warning: expression using sizeof bool
mm/gup.c:1247:24: warning: expression using sizeof(void)
mm/gup.c:1247:24: warning: expression using sizeof(void)
./arch/powerpc/include/asm/book3s/64/pgtable.h:667:20: warning:
incorrect type in initializer (different base types)
./arch/powerpc/include/asm/book3s/64/pgtable.h:667:20:    expected
unsigned long long [unsigned] [usertype] mask
./arch/powerpc/include/asm/book3s/64/pgtable.h:667:20:    got
restricted __be64 [usertype] <noident>
mm/gup.c:1735:6: warning: symbol 'gup_fast_permitted' was not
declared. Should it be static?
  CC      mm/gup.o


Also Sparse is throwing below warning ->

/Documents/linux-4.17-rc7$ make C=2 ARCH=powerpc
CROSS_COMPILE=powerpc-linux-gnu- mm/hugetlb.o

 CHK     include/config/kernel.release
  CHK     include/generated/uapi/linux/version.h
  CHK     include/generated/utsrelease.h
  CHK     include/generated/bounds.h
  CHK     include/generated/timeconst.h
  CHK     include/generated/asm-offsets.h
  CALL    scripts/checksyscalls.sh
  CHECK   scripts/mod/empty.c
  CHK     scripts/mod/devicetable-offsets.h
  CHECK   mm/hugetlb.c
mm/hugetlb.c:3778:33: warning: restricted vm_fault_t degrades to integer
mm/hugetlb.c:3777:31: warning: restricted vm_fault_t degrades to integer
mm/hugetlb.c:3777:29: warning: incorrect type in assignment (different
base types)
mm/hugetlb.c:3777:29:    expected restricted vm_fault_t [assigned]
[usertype] ret
mm/hugetlb.c:3777:29:    got unsigned int
mm/hugetlb.c:3895:33: warning: restricted vm_fault_t degrades to integer
mm/hugetlb.c:3894:32: warning: restricted vm_fault_t degrades to integer
mm/hugetlb.c:3894:56: warning: incorrect type in return expression
(different base types)
mm/hugetlb.c:3894:56:    expected restricted vm_fault_t
mm/hugetlb.c:3894:56:    got unsigned int

Which is fixed by ->

"#define VM_FAULT_SET_HINDEX(x) ((__force vm_fault_t)((x) << 16))"

in final vm_fault_t patch.

Does it looks good ?