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

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Date:   Fri, 4 Aug 2023 16:20:07 +0200
From:   Hannes Reinecke <hare@...e.de>
To:     Christoph Hellwig <hch@....de>,
        Sergey Senozhatsky <senozhatsky@...omium.org>
Cc:     Dusty Mabe <dusty@...tymabe.com>, wq@....de,
        Minchan Kim <minchan@...nel.org>, Jens Axboe <axboe@...nel.dk>,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>, marmijo@...hat.com
Subject: Re: XFS metadata CRC errors on zram block device on ppc64le
 architecture

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@...e.de                              +49 911 74053 688
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