linux-kernel - Re: [PATCH 09/16] ps3disk: use memcpy_{from,to}

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Message-ID: <20210611065338.GA31210@lst.de>
Date:   Fri, 11 Jun 2021 08:53:38 +0200
From:   Christoph Hellwig <hch@....de>
To:     Ira Weiny <ira.weiny@...el.com>
Cc:     Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Geoff Levand <geoff@...radead.org>,
        Ilya Dryomov <idryomov@...il.com>,
        Dongsheng Yang <dongsheng.yang@...ystack.cn>,
        Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        ceph-devel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        linux-arch@...r.kernel.org
Subject: Re: [PATCH 09/16] ps3disk: use memcpy_{from,to}_bvec

On Tue, Jun 08, 2021 at 06:48:22PM -0700, Ira Weiny wrote:
> I'm still not 100% sure that these flushes are needed but the are not no-ops on
> every arch.  Would it be best to preserve them after the memcpy_to/from_bvec()?
> 
> Same thing in patch 11 and 14.

To me it seems kunmap_local should basically always call the equivalent
of flush_kernel_dcache_page.  parisc does this through
kunmap_flush_on_unmap, but none of the other architectures with VIVT
caches or other coherency issues does.

Does anyone have a history or other insights here?