linux-kernel - Re: [PATCH v6 05/24] erofs: add inode operations

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Message-ID: <20190830164205.GD29603@infradead.org>
Date:   Fri, 30 Aug 2019 09:42:05 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Gao Xiang <gaoxiang25@...wei.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Theodore Ts'o <tytso@....edu>, Pavel Machek <pavel@...x.de>,
        David Sterba <dsterba@...e.cz>,
        Amir Goldstein <amir73il@...il.com>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        Dave Chinner <david@...morbit.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>, Jan Kara <jack@...e.cz>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, devel@...verdev.osuosl.org,
        LKML <linux-kernel@...r.kernel.org>,
        linux-erofs@...ts.ozlabs.org, Chao Yu <yuchao0@...wei.com>,
        Miao Xie <miaoxie@...wei.com>,
        Li Guifu <bluce.liguifu@...wei.com>,
        Fang Wei <fangwei1@...wei.com>
Subject: Re: [PATCH v6 05/24] erofs: add inode operations

On Thu, Aug 29, 2019 at 07:59:22PM +0800, Gao Xiang wrote:
> On Thu, Aug 29, 2019 at 03:24:26AM -0700, Christoph Hellwig wrote:
> 
> []
> 
> > 
> > > +
> > > +		/* fill last page if inline data is available */
> > > +		err = fill_inline_data(inode, data, ofs);
> > 
> > Well, I think you should move the is_inode_flat_inline and
> > (S_ISLNK(inode->i_mode) && inode->i_size < PAGE_SIZE) checks from that
> > helper here, as otherwise you make everyone wonder why you'd always
> > fill out the inline data.
> 
> Currently, fill_inline_data() only fills for fast symlink,
> later we can fill any tail-end block (such as dir block)
> for our requirements.

So change it when that later changes actually come in.  And even then
having the checks outside the function is a lot more obvious.

> And I think that is minor.

The problem is that each of these issues might appear minor on their
own.  But combined a lot of the coding style choices lead to code that
is more suitable an obsfucated code contest than the Linux kernel as
trying to understand even just a few places requires jumping through
tons of helpers with misleading names and spread over various files.

> The consideration is simply because iget_locked performs better
> than iget5_locked.

In what benchmark do the differences show up?