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

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Date:   Wed, 13 Jun 2018 07:42:53 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Christoph Hellwig <hch@...radead.org>, 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 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.

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)

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)