Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Fri, 4 Aug 2023 12:25:23 +0900
From:   Sergey Senozhatsky <senozhatsky@chromium.org>
To:     Dusty Mabe <dusty@dustymabe.com>
Cc:     Hannes Reinecke <hare@suse.de>, wq@lst.de,
        Minchan Kim <minchan@kernel.org>,
        Sergey Senozhatsky <senozhatsky@chromium.org>,
        Jens Axboe <axboe@kernel.dk>, linux-kernel@vger.kernel.org,
        linux-block@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
        Andrew Morton <akpm@linux-foundation.org>, marmijo@redhat.com
Subject: Re: XFS metadata CRC errors on zram block device on ppc64le
 architecture
Message-ID: <20230804032523.GA81493@google.com>
References: <b2d40565-7868-ba15-4bb1-fca6f0df076b@dustymabe.com>
 <20230802094106.GA28187@lst.de>
 <3f36882c-b429-3ece-989b-a6899c001cbd@suse.de>
 <43843fec-f30a-1edc-b428-1d38ddb1050f@dustymabe.com>
 <a0f05188-d142-82f2-74aa-6c9a6ae2bbc9@dustymabe.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <a0f05188-d142-82f2-74aa-6c9a6ae2bbc9@dustymabe.com>
Precedence: bulk

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.