Date: Wed, 11 Nov 2015 12:37:20 -0500
From: Mike Snitzer <snitzer@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Mike Christie <michaelc@cs.wisc.edu>, linux-scsi@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org,
        device-mapper development <dm-devel@redhat.com>,
        linux-fsdevel@vger.kernel.org,
        Bart Van Assche <bart.vanassche@sandisk.com>,
        drbd-dev@lists.linbit.com
Subject: Re: [RFC PATCH 00/32] separate operations from flags in the
 bio/request structs
Message-ID: <20151111173719.GB12236@redhat.com>
References: <1446654807-6935-1-git-send-email-mchristi@redhat.com>
 <563A36FC.6010001@sandisk.com>
 <563A3813.5010604@cs.wisc.edu>
 <20151107102309.GE12117@infradead.org>
 <5642F3F4.2060007@cs.wisc.edu>
 <20151111112846.GA358@infradead.org>
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On Wed, Nov 11 2015 at  6:28am -0500,
Christoph Hellwig <hch@infradead.org> wrote:

> On Wed, Nov 11, 2015 at 01:53:24AM -0600, Mike Christie wrote:
> > We no longer have the bvec merge functions so the original reason given
> > in the thread/patch Bart referenced is no longer valid.
> > 
> > Offlist it was suggested that dropping the argument from submit_bio
> > might still improve performance, but I modified xfs and dm and did some
> > testing and did not see anything.
> > 
> > So the change is not needed, and it would only be done because people
> > feel it would improve the interface.
> 
> I would defintively prefer the changed interface, and to me it also
> looks like it would make your overall patch simpler.  If you disagree
> feel free to keep it as-is for now and I'll do another pass later.

The less churn the better.  But honestly, not quite following the logic
on why all this flag-day churn is needed.  BUT if it needs to happen,
because we'll soon hit a wall on supported operations via REQ_*, now is
as good a time as any -- but best to limit the change to the flags IMHO.
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