linux-kernel - Re: [RESEND PATCH V5 00/33] block: support multipage bvec

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Date:   Mon, 28 May 2018 10:30:43 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Kent Overstreet <kent.overstreet@...il.com>,
        Christoph Hellwig <hch@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        David Sterba <dsterba@...e.cz>,
        Huang Ying <ying.huang@...el.com>,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        Theodore Ts'o <tytso@....edu>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        Coly Li <colyli@...e.de>, Filipe Manana <fdmanana@...il.com>
Subject: Re: [RESEND PATCH V5 00/33] block: support multipage bvec

On Sun, May 27, 2018 at 07:44:52PM -0600, Jens Axboe wrote:
> On 5/27/18 1:23 AM, Ming Lei wrote:
> > On Fri, May 25, 2018 at 10:30:46AM -0600, Jens Axboe wrote:
> >> On 5/24/18 10:53 PM, Kent Overstreet wrote:
> >>> On Fri, May 25, 2018 at 11:45:48AM +0800, Ming Lei wrote:
> >>>> Hi,
> >>>>
> >>>> This patchset brings multipage bvec into block layer:
> >>>
> >>> patch series looks sane to me. goddamn that's a lot of renaming.
> >>
> >> Indeed... I actually objected to some of the segment -> page
> >> renaming, but it's still in there. The foo2() temporary functions
> >> also concern me, we all know there's nothing more permanent than a
> >> temporary fixup.
> > 
> > Jens, I remember I explained the renaming story to you in lsfmm a bit:
> > 
> > 1) the current naming of segment is actually wrong, since every segment
> > only stores one single-page vector
> > 
> > 2) the most important part is that once multipage bvec is introduced,
> > if the old _segment naming is still kept, it can be very confusing,
> > especially no good name is left for the helpers of dealing with real
> > segment.
> 
> Yes, we discussed exactly this, which is why I'm surprised you went
> ahead with the same approach. I told you I don't like tree wide renames,

Maybe I misunderstood your point, that isn't strange given my poor
english, :-)

> if they can be avoided. I'd rather suffer some pain wrt page vs segments
> naming, and then later do a rename (if it bothers us) once the dust has
> settled on the interesting part of the changes.
> 
> I'm very well away of our current naming and what it signifies.  With
> #1, you are really splitting hairs, imho. Find a decent name for
> multiple segment. Chunk?

OK, will try _chunk in next post.

> 
> > For the foo2() temporary change, that is only for avoiding tree-wide
> > change in one single tree, with this way, we can change sub-system one
> > by one, but if you think it is good to do tree-wide conversion in one
> > patch, I am fine to do it in next version.
> 
> It's still a painful middle step.

I hate the conversion too, but looks it can't be avoided since
bio_for_each_segment_all() has to be changed.

Could you share us what your favorite approach is for this conversion?


Thanks,
Ming