linux-kernel - Re: [PATCH 2/2] mm: Make swap_readpage() for SWP_FS_OPS use ->direct

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Message-ID: <3088327.1628774588@warthog.procyon.org.uk>
Date:   Thu, 12 Aug 2021 14:23:08 +0100
From:   David Howells <dhowells@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     dhowells@...hat.com, trond.myklebust@...marydata.com,
        darrick.wong@...cle.com, hch@....de, jlayton@...nel.org,
        sfrench@...ba.org, torvalds@...ux-foundation.org,
        linux-nfs@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mm: Make swap_readpage() for SWP_FS_OPS use ->direct_IO() not ->readpage()

Matthew Wilcox <willy@...radead.org> wrote:

> After submitting the IO here ...
> 
> > +	if (ret != -EIOCBQUEUED)
> > +		swapfile_read_complete(&ki->iocb, ret, 0);
> 
> We only touch the 'ki' here ... if the caller didn't call read_complete
> 
> > +	swapfile_put_kiocb(ki);
> 
> Except for here, which is only touched in order to put the refcount.
> 
> So why can't swapfile_read_complete() do the work of freeing the ki?

When I was doing something similar for cachefiles, I couldn't get it to work
like that.  I'll have another look at that.

David