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List:       ocfs2-devel
Subject:    Re: [Ocfs2-devel] [PATCH 1/2] aio: make kiocb->private NUll in init_sync_kiocb()
From:       Jeff Moyer <jmoyer () redhat ! com>
Date:       2012-05-31 14:08:13
Message-ID: x49k3zscuk2.fsf () segfault ! boston ! devel ! redhat ! com
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Junxiao Bi <junxiao.bi@oracle.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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