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Message-ID: <3f36882c-b429-3ece-989b-a6899c001cbd@suse.de>
Date:   Wed, 2 Aug 2023 13:03:47 +0200
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Subject: Re: XFS metadata CRC errors on zram block device on ppc64le
 architecture
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To:     wq@lst.de, Dusty Mabe <dusty@dustymabe.com>
Cc:     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
References: <b2d40565-7868-ba15-4bb1-fca6f0df076b@dustymabe.com>
 <20230802094106.GA28187@lst.de>
From:   Hannes Reinecke <hare@suse.de>
In-Reply-To: <20230802094106.GA28187@lst.de>
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On 8/2/23 11:41, Christoph Hellwig wrote:
> On Tue, Aug 01, 2023 at 11:31:37PM -0400, Dusty Mabe wrote:
>> We ran a kernel bisect and narrowed it down to offending commit af8b04c6:
>>
>> ```
>> [root@ibm-p8-kvm-03-guest-02 linux]# git bisect good
>> af8b04c63708fa730c0257084fab91fb2a9cecc4 is the first bad commit
>> commit af8b04c63708fa730c0257084fab91fb2a9cecc4
>> Author: Christoph Hellwig <hch@lst.de>
>> Date:   Tue Apr 11 19:14:46 2023 +0200
>>
>>      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?

Cheers,

Hannes