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Date:   Tue, 8 Jun 2021 18:38:02 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Bart Van Assche <bvanassche@acm.org>
Cc:     Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
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        Ilya Dryomov <idryomov@gmail.com>,
        Dongsheng Yang <dongsheng.yang@easystack.cn>,
        Mike Snitzer <snitzer@redhat.com>,
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Subject: Re: [PATCH 08/16] dm-writecache: use bvec_kmap_local instead of
 bvec_kmap_irq
Message-ID: <20210608163802.GA12173@lst.de>
References: <20210608160603.1535935-1-hch@lst.de> <20210608160603.1535935-9-hch@lst.de> <4c248453-713f-9da8-04e8-7939388be49a@acm.org>
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On Tue, Jun 08, 2021 at 09:30:56AM -0700, Bart Van Assche wrote:
> >From one of the functions called by kunmap_local():
> 
> unsigned long addr = (unsigned long) vaddr & PAGE_MASK;
> 
> This won't work well if bvec->bv_offset >= PAGE_SIZE I assume?

It won't indeed.  Both the existing and new helpers operate on single
page bvecs only, and all callers only use those.  I should have
probably mentioned that in the cover letter and documented the
assumptions in the code, though.