[systemd-devel] Failed to open system journal: Invalid argument

[Kay One]

Hi Lennart,

Do you have any idea that UBIFS supports writable memory mappings or not?

Regards,
Karnik Jain

On Wed, May 22, 2019 at 12:05 AM Kay One <kayone007 at gmail.com> wrote:

> Thank you so much for your time.
> Let me try changing JFFS2 to UBIFS as another available option to use for
> my SOC.
>
> I would keep you guys posted.
>
> Regards,
> Karnik Jain
>
> On Tue, May 21, 2019 at 8:18 PM Lennart Poettering <lennart at poettering.net>
> wrote:
>
>> On Di, 21.05.19 17:37, Kay One (kayone007 at gmail.com) wrote:
>>
>> > Thanks for the reply Lennart.
>> >
>> > 1) mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, 28, 0) = -1
>> EINVAL
>> > > (Invalid argument) is the culprit for this error???
>>
>> Yes.
>>
>> > 2) If YES. Is this JFFS2 MTD file system bug or
>>
>> It's a missing feature of the fs implementation, that the journal
>> relies on. Memory mapping a file is not a particularly exotic feature,
>> and yes, file systems really should implement that.
>>
>> So my recommendation would be: work with the jffs2 folks to add this
>> to the kernel. They already have it for PROT_READ afaik, doing it for
>> PROT_WRITE is extra work, and not trivial but it will fix jffs2 for
>> every program that uses mmap for writing, and journald is just one of
>> them.
>>
>> > 3) Is this not considered as systemd bug to support compatibility for
>> such
>> > file system? Check first FS support writable mappings or not and if not
>> > then use other method to enable Persistence logging for systemd?
>>
>> I think it's better to fix jffs2 in this regard than to add a
>> userspace workaround to every single consumer of it.
>>
>> Doing this without mmap() is not trivial, and I don't see anyone
>> stepping up to do the work. It wouldn't precisely make our codebase
>> easier to read either...
>>
>> Lennart
>>
>> --
>> Lennart Poettering, Berlin
>>
>
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