linux-kernel - Re: [RFC PATCH v3 07/26] iomap: don't increase i

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Message-ID: <ZdKTFp4v1kQuLg9e@dread.disaster.area>
Date: Mon, 19 Feb 2024 10:30:30 +1100
From: Dave Chinner <david@...morbit.com>
To: Zhang Yi <yi.zhang@...weicloud.com>
Cc: Christoph Hellwig <hch@...radead.org>, linux-ext4@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, tytso@....edu,
	adilger.kernel@...ger.ca, jack@...e.cz, ritesh.list@...il.com,
	djwong@...nel.org, willy@...radead.org, zokeefe@...gle.com,
	yi.zhang@...wei.com, chengzhihao1@...wei.com, yukuai3@...wei.com,
	wangkefeng.wang@...wei.com
Subject: Re: [RFC PATCH v3 07/26] iomap: don't increase i_size if it's not a
 write operation

On Sat, Feb 17, 2024 at 04:55:51PM +0800, Zhang Yi wrote:
> On 2024/2/13 13:46, Christoph Hellwig wrote:
> > Wouldn't it make more sense to just move the size manipulation to the
> > write-only code?  An untested version of that is below.  With this
> 
> Sorry for the late reply and thanks for your suggestion, The reason why
> I introduced this new helper iomap_write_end_simple() is I don't want to
> open code __iomap_put_folio() in each caller since corresponding to
> iomap_write_begin(), it's the responsibility for iomap_write_end_*() to
> put and unlock folio, so I'd like to keep it in iomap_write_end_*().

Just because we currently put the folio in iomap_write_end_*(), it
doesn't mean we must always do it that way.

> But I don't feel strongly about it, it's also fine by me to just move
> the size manipulation to the write-only code if you think it's better.

I agree with Christoph that it's better to move the i_size update
into iomap_write_iter() than it is to implement a separate write_end
function that does not update the i_size. The iter functions already
do work directly on the folio that iomap_write_begin() returns, so
having them drop the folio when everything is done isn't a huge
deal...

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com