Re: [PATCH v4 1/2] aio: make kiocb->private NUll ininit_sync_kiocb()

[Joel Becker]

On Fri, Jun 29, 2012 at 06:49:43PM +0800, Junxiao Bi wrote:
> On 06/29/2012 05:22 PM, Joel Becker wrote:
> > On Thu, Jun 28, 2012 at 03:39:56PM -0700, Andrew Morton wrote:
> >> On Wed, 27 Jun 2012 17:09:54 +0800
> >> Junxiao Bi <junxiao.bi@xxxxxxxxxx> wrote:
> >>
> >>> 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_aio_write().
> >>>
> >>> Signed-off-by: Junxiao Bi <junxiao.bi@xxxxxxxxxx>
> >>> Cc: stable@xxxxxxxxxxxxxxx
> >>> Acked-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
> >>> Acked-by: Joel Becker <jlbec@xxxxxxxxxxxx>
> >>> ---
> >>>  include/linux/aio.h |    1 +
> >>>  1 file changed, 1 insertion(+)
> >>>
> >>> diff --git a/include/linux/aio.h b/include/linux/aio.h
> >>> index 2314ad8..b1a520e 100644
> >>> --- a/include/linux/aio.h
> >>> +++ b/include/linux/aio.h
> >>> @@ -140,6 +140,7 @@ struct kiocb {
> >>>  		(x)->ki_dtor = NULL;			\
> >>>  		(x)->ki_obj.tsk = tsk;			\
> >>>  		(x)->ki_user_data = 0;                  \
> >>> +		(x)->private = NULL;			\
> >>>  	} while (0)
> >>>  
> >>>  #define AIO_RING_MAGIC			0xa10a10a1
> >> hm, that code is rather cruddy.  Pointless macromania.
> > Agreed.
> >
> >> If we do this:
> >>
> >> static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
> >> {
> >> 	*kiocb = (struct kiocb) {
> >> 			.ki_users = 1,
> >> 			.ki_key = KIOCB_SYNC_KEY,
> >> 			.ki_filp = filp,
> >> 			.ki_obj.tsk = current,
> >> 		};
> >> }
> >>
> >> then fs/read_write.o's .text is shrunk from 9857 bytes to 9714, which
> >> is rather a lot.
> >>
> >> But that's all rather irrelevant to your bugfix.
> > 	I like your solution.  Junxiao, if you send me that version, I'd
> > be happy to take it.
> Joel, since Andrew will feed his cleanup patch later on. Please help
> merge my patches. Though it is covered by the cleanup patch, but I think
> it's useful to merge it, at least we can see from the git log this is
> for an ocfs2 hang bug.

Yes, I'll be pulling it.

Joel

> >
> > Joel
> >
> 

-- 

"In the room the women come and go
 Talking of Michaelangelo."

			http://www.jlbec.org/
			jlbec@xxxxxxxxxxxx
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