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;
Message-ID: <273c9c99-dc2f-2854-bbc1-70b22b5589d8@suse.de>
Date:   Fri, 4 Aug 2023 16:20:07 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.12.0
Subject: Re: XFS metadata CRC errors on zram block device on ppc64le
 architecture
Content-Language: en-US
To:     Christoph Hellwig <hch@lst.de>,
        Sergey Senozhatsky <senozhatsky@chromium.org>
Cc:     Dusty Mabe <dusty@dustymabe.com>, wq@lst.de,
        Minchan Kim <minchan@kernel.org>, Jens Axboe <axboe@kernel.dk>,
        linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>, marmijo@redhat.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>
 <20230804032523.GA81493@google.com> <20230804134248.GA26611@lst.de>
From:   Hannes Reinecke <hare@suse.de>
In-Reply-To: <20230804134248.GA26611@lst.de>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 8/4/23 15:42, Christoph Hellwig wrote:
> FYI, I've found an arm64 system with 16k page size support, and while
> I can't reproduce the exact issue, I do see corruption with I/O test
> on zram that don't show on the same system with 4k pages.  I'm trying
> to understand the details at the moment.
> 
For some reason zram run with a logical block size of 4k:

#define ZRAM_LOGICAL_BLOCK_SHIFT 12
#define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT)

so we'll have sub-page accesses for larger page sizes.
My bet is that the issue goes away if we set the logical block size to 
page size ...

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman