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

[Christoph Hellwig]

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@xxxxxx>
> 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.