Re: PROBLEM: selftest/vm/cow.c failed to compile (‘MADV_PAGEOUT’ undeclared)

[David Hildenbrand]

On 09.01.23 22:41, Mirsad Goran Todorovac wrote:
> On 1/9/2023 5:42 PM, David Hildenbrand wrote:
>
> Hi, thank you for your reply.
>
> > > I hope this is enough information for you to debug the issue.
> > >
> > > I am standing by for any additional diagnostics needed.
> >
> > Won't userfaultfd.c fail in a similar way?
> >
> > Anyhow, khugepaged.c jas
> >
> > #ifndef MADV_PAGEOUT
> > #define MADV_PAGEOUT 21
> > #endif
> >
> > So most probably we should do the same.
>
> Actually, David, it turned out that userfaultfd.c compiled
> out-of-the-box, and side-by-side comparison showed that it also included
> "/home/marvin/linux/kernel/linux_torvalds/usr/include/asm-generic/mman-common.h"
>
> The only remaining difference was including <linux/mman.h>, which fixed
> the issue w/o #ifdef ... #endif
>
> Hope this helps.
>
> Please find the following diff.
>
> Regards,
> Mirsad
>
> ------------------------------------------------------------------------------
> diff --git a/tools/testing/selftests/vm/cow.c
> b/tools/testing/selftests/vm/cow.c
> index 26f6ea3079e2..dd8cf12c6776 100644
> --- a/tools/testing/selftests/vm/cow.c
> +++ b/tools/testing/selftests/vm/cow.c
> @@ -16,6 +16,7 @@
>    #include <fcntl.h>
>    #include <dirent.h>
>    #include <assert.h>
> +#include <linux/mman.h>
>    #include <sys/mman.h>
>    #include <sys/ioctl.h>
>    #include <sys/wait.h>

I already sent a different fix [1]. I suspect when including
linux/mman.h, it would still be problematic with older kernel
headers that lack MADV_PAGEOUT (< v5.4).


But yeah, I saw that userfaultfd.c was fixed that way:

commit b773827e361952b3f53ac6fa4c4e39ccd632102e
Author: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Date:   Fri Mar 4 20:29:04 2022 -0800

    kselftest/vm: fix tests build with old libc
    
    The error message when I build vm tests on debian10 (GLIBC 2.28):
    
        userfaultfd.c: In function `userfaultfd_pagemap_test':
        userfaultfd.c:1393:37: error: `MADV_PAGEOUT' undeclared (first use
        in this function); did you mean `MADV_RANDOM'?
          if (madvise(area_dst, test_pgsize, MADV_PAGEOUT))
                                             ^~~~~~~~~~~~
                                             MADV_RANDOM
    
    This patch includes these newer definitions from UAPI linux/mman.h, is
    useful to fix tests build on systems without these definitions in glibc
    sys/mman.h.


[1] https://lkml.kernel.org/r/20230109171255.488749-1-david@xxxxxxxxxx

--
Thanks,

David / dhildenb