[Crash-utility] EXT: RE: crash: read error on type: "memory section root table"

[HAGIO KAZUHITO(萩尾 一仁)]

On 2022/07/22 21:04, Agrain Patrick wrote:
> Hello,
> 
> Back to this topic.
> 
> I upgraded our system with the kexec-tools from Centos 8 Stream, based on kexec 2.0.24 and makedumpfile 1.7.1.
> We are still facing errors when using 'makedumpfile -c'.
> 
> Removing the '-c' gives better ratio success/failure, but sometimes the crash file cannot be read by the crash tool.
> 
> Referring to Hagio's remark below concerning the sync, I added a sync operation before the call of makedumpfile (and just after the mount ext4 of the required partitions) and add a second call to sync after the return of makedumpfile.
> In that configuration, the crash file can be read by the crash tool (up to now in all cases).

Good, seems the second sync works.  I would suggest unmounting the filesystem
cleanly, which contains syncing to disk, before reboot, if you don't do that.

Thanks,
Kazu

> 
> Thanks for your help.
> Best regards,
> Patrick Agrain
> 
> -----Message d'origine-----
> De : Crash-utility <crash-utility-bounces at redhat.com> De la part de Agrain Patrick
> Envoyé : mercredi 6 avril 2022 17:48
> À : Discussion list for crash utility usage, maintenance and development <crash-utility at redhat.com>; kexec at lists.infradead.org
> Objet : Re: [Crash-utility] EXT: RE: crash: read error on type: "memory section root table"
> 
> 
> 
> -----Message d'origine-----
> De : HAGIO KAZUHITO(萩尾　一仁) <k-hagio-ab at nec.com> Envoyé : mercredi 6 avril 2022 09:48 À : Agrain Patrick <patrick.agrain at al-enterprise.com>
> Cc : Discussion list for crash utility usage, maintenance and development <crash-utility at redhat.com>; kexec at lists.infradead.org Objet : RE: EXT: RE: crash: read error on type: "memory section root table"
> 
> -----Original Message-----
>> Hello,
>>
>> Suggested trace above gives following information after a crash -d 8 command:
>> <...>
>> kernel NR_CPUS: 2
>> <readmem: ffffffffa4925820, KVADDR, "high_memory", 8, (FOE),
>> 56017b542648>
>> <read_diskdump: addr: ffffffffa4925820 paddr: 12925820 cnt: 8>
>> read_diskdump: paddr/pfn: 12925820/12925 -> cache physical page:
>> 12925000
>> GETBUF(328 -> 0)
>> FREEBUF(0)
>> GETBUF(328 -> 0)
>> FREEBUF(0)
>> PAGESIZE=4096
>> mem_section_size = 16384
>> NR_SECTION_ROOTS = 2048
>> NR_MEM_SECTIONS = 524288
>> SECTIONS_PER_ROOT = 256
>> SECTION_ROOT_MASK = 0xff
>> PAGES_PER_SECTION = 32768
>> <readmem: ffffffffa4926db0, KVADDR, "mem_section", 8, (FOE),
>> 7ffd1b6bb000>
>> <read_diskdump: addr: ffffffffa4926db0 paddr: 12926db0 cnt: 8>
>> read_diskdump: paddr/pfn: 12926db0/12926 -> cache physical page:
>> 12926000
>> <readmem: ffff904c7f7fc000, KVADDR, "memory section root table",
>> 16384, (FOE), 56017da26fd0>
>> <read_diskdump: addr: ffff904c7f7fc000 paddr: 3f7fc000 cnt: 4096>
>> read_diskdump: paddr/pfn: 3f7fc000/3f7fc -> cache physical page:
>> 3f7fc000
>> crash: PAG3 - errno=2 r=0 pd.size=49
>> read_diskdump: READ_ERROR: cannot cache page: 3f7fc000
>> crash: read error: kernel virtual address: ffff904c7f7fc000  type: "memory section root table"
> 
> hmm, r=0 means end of file, can you check again whether pd.offset exceeds the dumpfile size?  If so, somehow the dumpfile is shorter than expected.
> 
> Indeed, the offset points outside the dumpfile:
> Get:
> crash: PAG3 - errno=2 r=0 pd.size=52 pd.offset=168956485 with a dumpfile
> 164820 -rw-r--r--.  1 root root  168775680  6 avril 17:23 crashdump--20220406-1713
> 
> And another one:
> Get:
> crash: PAG3 - errno=2 r=0 pd.size=49 pd.offset=215640649 with a dumpfile
> 209984 -rw-r--r--.  1 root root  215023616  1 avril 10:58 crashdump-585.000-20220401-1054
> 
> I think a RHEL-based kexec-tools does "sync" after makedumpfile, but can you check?
> 
> Actually, we are executing the makedumpfile in a script designated as init file for the second kernel. Therefore, we do not perform the sync as per core_collector.
> 
> Thanks,
> Kazu
> 
> Best regards,
> Patrick
> 
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