linux-kernel - Re: [PATCH 1/2] aio: make kiocb->private NUll in init_sync

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Message-ID: <x49k3zscuk2.fsf@segfault.boston.devel.redhat.com>
Date:	Thu, 31 May 2012 10:08:13 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Junxiao Bi <junxiao.bi@...cle.com>
Cc:	ocfs2-devel@....oracle.com, linux-aio@...ck.org, mfasheh@...e.com,
	jlbec@...lplan.org, bcrl@...ck.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org, joe.jin@...cle.com
Subject: Re: [PATCH 1/2] aio: make kiocb->private NUll in init_sync_kiocb()

Junxiao Bi <junxiao.bi@...cle.com> writes:

> Ocfs2 uses kiocb.*private as a flag of unsigned long size. In
> commit a11f7e6 ocfs2: serialize unaligned aio, the unaligned
> io flag is involved in it to serialize the unaligned aio. As
> *private is not initialized in init_sync_kiocb() of do_sync_write(),
> this unaligned io flag may be unexpectly set in an aligned dio.
> And this will cause OCFS2_I(inode)->ip_unaligned_aio decreased
> to -1 in ocfs2_dio_end_io(), thus the following unaligned dio
> will hang forever at ocfs2_aiodio_wait() in ocfs2_file_write_iter().

> We can't initialized this flag in ocfs2_file_write_iter() since
> it may be invoked several times by do_sync_write(). So we initialize
> it in init_sync_kiocb(), it's also useful for other similiar use of
> it in the future.

I don't see any ocfs2_file_write_iter in the upstream kernel.
ocfs2_file_aio_write most certainly could set ->private to 0, it
will only be called once for a given kiocb.

That point aside, I have no issues with setting private to NULL in
init_sync_kiocb.  If you fix up the comment to reflect reality
w.r.t. the upstream kernel source, I'll ack the patch.

Cheers,
Jeff
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