linux-ext4 - Re: Is ext4_dio_read_iter() broken?

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Date:   Thu, 12 Mar 2020 11:53:45 +0100
From:   Christoph Hellwig <hch@....de>
To:     David Howells <dhowells@...hat.com>
Cc:     Christoph Hellwig <hch@....de>, mbobrowski@...browski.org,
        darrick.wong@...cle.com, jack@...e.cz, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: Is ext4_dio_read_iter() broken? - and xfs_file_dio_aio_read()

On Thu, Mar 12, 2020 at 10:49:40AM +0000, David Howells wrote:
> Christoph Hellwig <hch@....de> wrote:
> 
> > > > at the end of the function - but surely iocb should be expected to have
> > > > been freed when iocb->ki_complete() was called?
> > 
> > The iocb is refcounted and only completed when the refcount hits zero,
> > and an extra reference is held until the submission has completed.
> > Take a look at iocb_put().
> 
> Ah...  This is in struct aio_kiocb and not struct kiocb - that's why I missed
> it.  Thanks.

That being said we have a few other spots using ->ki_complete for
asynchronous execution, which might not be as careful.  As someone
having written one or two of those I have my doubts I got everthing
right and will audit those.

> 
> David
---end quoted text---