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

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Date:   Tue, 8 Jun 2021 18:48:22 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Christoph Hellwig <hch@....de>
Cc:     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
Subject: Re: [PATCH 09/16] ps3disk: use memcpy_{from,to}_bvec

On Tue, Jun 08, 2021 at 06:05:56PM +0200, Christoph Hellwig wrote:
>  
>  	rq_for_each_segment(bvec, req, iter) {
> -		unsigned long flags;
> -		dev_dbg(&dev->sbd.core, "%s:%u: bio %u: %u sectors from %llu\n",
> -			__func__, __LINE__, i, bio_sectors(iter.bio),
> -			iter.bio->bi_iter.bi_sector);
> -
> -		size = bvec.bv_len;
> -		buf = bvec_kmap_irq(&bvec, &flags);
>  		if (gather)
> -			memcpy(dev->bounce_buf+offset, buf, size);
> +			memcpy_from_bvec(dev->bounce_buf + offset, &bvec);
>  		else
> -			memcpy(buf, dev->bounce_buf+offset, size);
> -		offset += size;
> -		flush_kernel_dcache_page(bvec.bv_page);

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.

Ira