Ocfs2 devel - Jun 2012 - [V3]fix ocfs2 aio/dio writing process hang

V3 changes:
- add Cc: stable at vger.kernel.org in the patch header to align with stable
rules
- add Acked-by: Jeff Moyer <jmoyer at redhat.com>

V2 changes:
- update the patch header of the first patch to make it more clear.


This patch list fixes an issue about ocfs2 aio/dio write process hang.
The call trace is like this:
@  cat /proc/15913/stack
@ [<ffffffffa06e1085>] ocfs2_aiodio_wait+0x85/0xc0 [ocfs2]
@ [<ffffffffa06e3e39>] ocfs2_file_aio_write+0x99/0xa0 [ocfs2]
@ [<ffffffff811ace97>] aio_rw_vect_retry+0x87/0x150
@ [<ffffffff811aebd1>] aio_run_iocb+0x71/0x170
@ [<ffffffff811af59b>] io_submit_one+0x1ab/0x280
@ [<ffffffff811af77c>] do_io_submit+0x10c/0x1c0
@ [<ffffffff811af840>] sys_io_submit+0x10/0x20
@ [<ffffffff81509b42>] system_call_fastpath+0x16/0x1b
@ [<ffffffffffffffff>] 0xffffffffffffffff

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 at oracle.com>
Cc: stable at vger.kernel.org
Acked-by: Jeff Moyer <jmoyer at redhat.com>
---
 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
-- 
1.7.9.5

The unaligned io flag is set in the kiocb when an unaligned
dio is issued, it should be cleared even when the dio fails,
or it may affect the following io which are using the same
kiocb.

Signed-off-by: Junxiao Bi <junxiao.bi at oracle.com>
Cc: stable at vger.kernel.org
---
 fs/ocfs2/file.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 061591a..98513c8 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -2422,8 +2422,10 @@ out_dio:
 		unaligned_dio = 0;
 	}
 
-	if (unaligned_dio)
+	if (unaligned_dio) {
+		ocfs2_iocb_clear_unaligned_aio(iocb);
 		atomic_dec(&OCFS2_I(inode)->ip_unaligned_aio);
+	}
 
 out:
 	if (rw_level != -1)
-- 
1.7.9.5

On Fri, Jun 08, 2012 at 02:08:04PM +0800, Junxiao Bi
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 at oracle.com>
> Cc: stable at vger.kernel.org
> Acked-by: Jeff Moyer <jmoyer at redhat.com>
Acked-by: Joel Becker <jlbec at evilplan.org>
> ---
>  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
> -- 
> 1.7.9.5
> 
-- 

"We will have to repent in this generation not merely for the
 vitriolic words and actions of the bad people, but for the 
 appalling silence of the good people."
	- Rev. Dr. Martin Luther King, Jr.

			http://www.jlbec.org/
			jlbec at evilplan.org