linux-kernel - Re: [PATCH v7 14/24] btrfs: Convert from readpages to readahead

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Message-ID: <20200220134849.GV24185@bombadil.infradead.org>
Date:   Thu, 20 Feb 2020 05:48:49 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Johannes Thumshirn <Johannes.Thumshirn@....com>
Cc:     "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>,
        "linux-erofs@...ts.ozlabs.org" <linux-erofs@...ts.ozlabs.org>,
        "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
        "linux-f2fs-devel@...ts.sourceforge.net" 
        <linux-f2fs-devel@...ts.sourceforge.net>,
        "cluster-devel@...hat.com" <cluster-devel@...hat.com>,
        "ocfs2-devel@....oracle.com" <ocfs2-devel@....oracle.com>,
        "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>
Subject: Re: [PATCH v7 14/24] btrfs: Convert from readpages to readahead

On Thu, Feb 20, 2020 at 09:42:19AM +0000, Johannes Thumshirn wrote:
> On 19/02/2020 22:03, Matthew Wilcox wrote:
> > From: "Matthew Wilcox (Oracle)" <willy@...radead.org>
> > 
> > Use the new readahead operation in btrfs.  Add a
> > readahead_for_each_batch() iterator to optimise the loop in the XArray.
> 
> OK I must admit I haven't followed this series closely, but what 
> happened to said readahead_for_each_batch()?
> 
> As far as I can see it's now:
> 
> [...]
> > +	while ((nr = readahead_page_batch(rac, pagepool))) {

Oops, forgot to update the changelog there.  Yes, that's exactly what it
changed to.  That discussion was here:

https://lore.kernel.org/linux-fsdevel/20200219144117.GP24185@bombadil.infradead.org/

... and then Christoph pointed out the iterators weren't really adding
much value at that point, so they got deleted.  New changelog for
this patch:

btrfs: Convert from readpages to readahead
  
Implement the new readahead method in btrfs.  Add a readahead_page_batch()
to optimise fetching a batch of pages at once.