linux-kernel - Re: [PATCH V6 00/30] block: support multipage bvec

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Message-ID: <20180614011852.GA19828@ming.t460p>
Date:   Thu, 14 Jun 2018 09:18:58 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Jens Axboe <axboe@...com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Kent Overstreet <kent.overstreet@...il.com>,
        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>,
        Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [PATCH V6 00/30] block: support multipage bvec

On Wed, Jun 13, 2018 at 07:42:53AM -0700, Christoph Hellwig wrote:
> On Tue, Jun 12, 2018 at 11:42:49AM +0800, Ming Lei wrote:
> > On Mon, Jun 11, 2018 at 09:48:06AM -0700, Christoph Hellwig wrote:
> > > І think the new naming scheme in this series is a nightmare.  It
> > > confuses the heck out of me, and that is despite knowing many bits of
> > > the block layer inside out, and reviewing previous series.
> > 
> > In V5, there isn't such issue, since bio_for_each_segment* is renamed
> > into bio_for_each_page* first before doing the change.
> 
> But now we are at V6 where that isn't the case..
> 
> > Seems Jens isn't fine with the big renaming, then I follow the suggestion
> > of taking 'chunk' for representing multipage bvec in V6.
> 
> Please don't use chunk.  We are iterating over bio_vec structures, while
> we have the concept of a chunk size for something else in the block layer,
> so this just creates confusion.  Nevermind names like
> bio_for_each_chunk_segment_all which just double the confusion.

We may keep the name of bio_for_each_segment_all(), and just change
the prototype in one single big patch.

> 
> So assuming that bio_for_each_segment is set to stay as-is for now,
> here is a proposal for sanity by using the vec name.
> 
> OLD:	    bio_for_each_segment
> NEW(page):  bio_for_each_segment, to be renamed bio_for_each_page later
> NEW(bvec):  bio_for_each_bvec
> 
> OLD:	    __bio_for_each_segment
> NEW(page):  __bio_for_each_segment, to be renamed __bio_for_each_page later
> NEW(bvec):  (no bvec version needed)

For the above two, basically similar with V6, just V6 takes chunk, :-)

> 
> OLD:	    bio_for_each_segment_all
> NEW(page):  bio_for_each_page_all (needs updated prototype anyway)
> NEW(bvec):  (no bvec version needed once bcache is fixed up)	

This one may cause confusing, since we iterate over pages via
bio_for_each_segment(), but the _all version takes another name
of page, still iterate over pages.

So could we change it in the following way?

 OLD:	    bio_for_each_segment_all
 NEW(page): bio_for_each_segment_all (update prototype in one tree-wide &
 			big patch, to be renamed bio_for_each_page_all)
 NEW(bvec):  (no bvec version needed once bcache is fixed up)	


Thanks,
Ming