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Date: Sun, 28 Oct 2018 16:49:47 +0100
From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        linux-block@vger.kernel.org,
        Rui Salvaterra <rsalvaterra@gmail.com>, stable@vger.kernel.org,
        Mike Snitzer <snitzer@redhat.com>, Xiao Ni <xni@redhat.com>,
        Mariusz Dabrowski <mariusz.dabrowski@intel.com>
Subject: Re: [PATCH 1/3] block: make sure discard bio is aligned with
 logical block size
Message-ID: <20181028154947.GB3061@lst.de>
References: <20181026062435.21398-1-ming.lei@redhat.com> <20181026062435.21398-2-ming.lei@redhat.com> <20181026074415.GA4660@lst.de> <20181028005130.GA26731@ming.t460p>
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On Sun, Oct 28, 2018 at 08:51:31AM +0800, Ming Lei wrote:
> On Fri, Oct 26, 2018 at 09:44:15AM +0200, Christoph Hellwig wrote:
> > >  		if (req_sects > UINT_MAX >> 9)
> > > -			req_sects = UINT_MAX >> 9;
> > > +			req_sects = (UINT_MAX >> 9) & ~bs_mask;
> > 
> > Given that we have this same thing duplicated in write zeroes
> > what about a documented helper?
> 
> IMO, using UINT_MAX & bs_mask is better because it is self-explanatory
> in the context.

I don't think it is in any way.  I understand it because I know the
code, but there is nothing that documents why we do that.