linux-kernel - Re: [PATCH 4/4] Revert "mm/page_alloc: make should_fail_alloc

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Date:   Thu, 15 Jul 2021 10:35:09 +0200
From:   Jesper Dangaard Brouer <jbrouer@...hat.com>
To:     John Hubbard <jhubbard@...dia.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Andrew Morton <akpm@...ux-foundation.org>, acme@...nel.org,
        Jiri Olsa <jolsa@...hat.com>
Cc:     brouer@...hat.com,
        Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>,
        Zhang Qiang <Qiang.Zhang@...driver.com>,
        Yanfei Xu <yanfei.xu@...driver.com>,
        Chuck Lever <chuck.lever@...cle.com>,
        Matteo Croce <mcroce@...rosoft.com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH 4/4] Revert "mm/page_alloc: make should_fail_alloc_page()
 static"

Cc. Jiri Olsa + Arnaldo

On 14/07/2021 09.06, John Hubbard wrote:
> On 7/13/21 8:21 AM, Mel Gorman wrote:
>> From: Matteo Croce <mcroce@...rosoft.com>
>>
>> This reverts commit f7173090033c70886d925995e9dfdfb76dbb2441.
>>
>> Fix an unresolved symbol error when CONFIG_DEBUG_INFO_BTF=y:
>>
>>    LD      vmlinux
>>    BTFIDS  vmlinux
>> FAILED unresolved symbol should_fail_alloc_page
>> make: *** [Makefile:1199: vmlinux] Error 255
>> make: *** Deleting file 'vmlinux'
> 
> Yes! I ran into this yesterday. Your patch fixes this build failure
> for me, so feel free to add:
> 
> Tested-by: John Hubbard <jhubbard@...dia.com>
> 
> 
> However, I should add that I'm still seeing another build failure, after
> fixing the above:
> 
> LD      vmlinux
> BTFIDS  vmlinux
> FAILED elf_update(WRITE): no error

This elf_update(WRITE) error is new to me.

> make: *** [Makefile:1176: vmlinux] Error 255
> make: *** Deleting file 'vmlinux'

It is annoying that vmlinux is deleted in this case, because I usually 
give Jiri the output from 'resolve_btfids -v' on vmlinux.

  $ ./tools/bpf/resolve_btfids/resolve_btfids -v vmlinux.failed

You can do:
$ git diff
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 3b261b0f74f0..02dec10a7d75 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -302,7 +302,8 @@ cleanup()
         rm -f .tmp_symversions.lds
         rm -f .tmp_vmlinux*
         rm -f System.map
-       rm -f vmlinux
+       # rm -f vmlinux
+       mv vmlinux vmlinux.failed
         rm -f vmlinux.o
  }


> 
> 
> ...and un-setting CONFIG_DEBUG_INFO_BTF makes that disappear. Maybe someone
> who is understands the BTFIDS build step can shed some light on that; I'm
> not there yet. :)

I'm just a user/consume of output from the BTFIDS build step, I think 
Jiri Olsa own the tool resolve_btfids, and ACME pahole.  I've hit a 
number of issues in the past that Jiri and ACME help resolve quickly.
The most efficient solution I've found was to upgrade pahole to a newer 
version.

What version of pahole does your build system have?

What is your GCC version?

--Jesper