linux-ext4 - Re: [RFC 2/3] ext2: Convert ext2 regular file buffered I/O to use iomap

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Message-ID: <ZV6AJHd0jJ14unJn@dread.disaster.area>
Date: Thu, 23 Nov 2023 09:26:44 +1100
From: Dave Chinner <david@...morbit.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: Jan Kara <jack@...e.cz>, "Ritesh Harjani (IBM)" <ritesh.list@...il.com>,
	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [RFC 2/3] ext2: Convert ext2 regular file buffered I/O to use
 iomap

On Wed, Nov 22, 2023 at 05:11:18AM -0800, Christoph Hellwig wrote:
> On Wed, Nov 22, 2023 at 01:29:46PM +0100, Jan Kara wrote:
> > writeback bit set. XFS plays the revalidation sequence counter games
> > because of this so we'd have to do something similar for ext2. Not that I'd
> > care as much about ext2 writeback performance but it should not be that
> > hard and we'll definitely need some similar solution for ext4 anyway. Can
> > you give that a try (as a followup "performance improvement" patch).
> 
> Darrick has mentioned that he is looking into lifting more of the
> validation sequence counter validation into iomap.

I think that was me, as part of aligning the writeback path with
the ->iomap_valid() checks in the write path after we lock the folio
we instantiated for the write.

It's basically the same thing - once we have a locked folio, we have
to check that the cached iomap is still valid before we use it for
anything.

I need to find the time to get back to that, though.

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