linux-kernel - Re: XFS metadata CRC errors on zram block device on ppc64le architecture

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Date:   Fri, 4 Aug 2023 12:25:23 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Dusty Mabe <dusty@...tymabe.com>
Cc:     Hannes Reinecke <hare@...e.de>, wq@....de,
        Minchan Kim <minchan@...nel.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>, marmijo@...hat.com
Subject: Re: XFS metadata CRC errors on zram block device on ppc64le
 architecture

On (23/08/03 17:32), Dusty Mabe wrote:
> >>>>      zram: simplify bvec iteration in __zram_make_request
> >>>>      
> >>>>      bio_for_each_segment synthetize bvecs that never cross page boundaries, so
> >>>>      don't duplicate that work in an inner loop.
> >>>
> >>>> Any ideas on how to fix the problem?
> >>>
> >>> So the interesting cases are:
> >>>
> >>>    - ppc64 usually uses 64k page sizes
> >>>    - ppc64 is somewhat cache incoherent (compared to say x86)
> >>>
> >>> Let me think of this a bit more.
> >>
> >> Would need to be confirmed first that 64k pages really are in use
> >> (eg we compile ppc64le with 4k page sizes ...).
> >> Dusty?
> >> For which page size did you compile your kernel?
> > 
> > 
> > For Fedora the configuration is to enable 64k pages with CONFIG_PPC_64K_PAGES=y
> > https://src.fedoraproject.org/rpms/kernel/blob/064c1675a16b4d379b42ab6c3397632ca54ad897/f/kernel-ppc64le-fedora.config#_4791
> > 
> > I used the same configuration when running the git bisect.
> 
> Naive question from my side: would this be a candidate for reverting while we investigate the root cause?

That's certainly a possible solution.

But I don't quite understand why af8b04c63708 doesn't work.