linux-kernel - Re: [PATCH 2/3] aio: fix oops because of extra IO control block freeing.

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Message-ID: <Pine.LNX.4.44L0.0703051428150.3843-100000@iolanthe.rowland.org>
Date:	Mon, 5 Mar 2007 14:35:37 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	leonid.i.ananiev@...el.com
cc:	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] aio: fix oops because of extra IO control block
 freeing.

On Mon, 5 Mar 2007, Leonid Ananiev wrote:

>  From Leonid Ananiev
> 
> This patch finishes moving from using errno EIOCBRETRY to using flag in 
> IO control block for aio retrying. After this change the process will be 
> kicked for direct aio as it was for sync aio.
> 
> Signed-off-by: Leonid Ananiev <leonid.i.ananiev@...el.com>
> 
> The patch is applied to 2.6.20 or 2.6.21-rc2
> diff -uprN -X linux-2.6.20-aio21/Documentation/dontdiff 
> linux-2.6.20-aio21/drivers/usb/gadget/inode.c 
> linux-2.6.20-aio22/drivers/usb/gadget/inode.c
> --- linux-2.6.20-aio21/drivers/usb/gadget/inode.c	2007-03-04 
> 21:45:52.000000000 +0300
> +++ linux-2.6.20-aio22/drivers/usb/gadget/inode.c	2007-03-05 
> 18:19:35.000000000 +0300
> @@ -692,7 +692,10 @@ fail:
>   		kfree(priv);
>   		put_ep(epdata);
>   	} else
> -		value = (iv ? -EIOCBRETRY : -EIOCBQUEUED);
> +		if (iv)
> +			kiocbSetPgBusy(iocb);
> +		else
> +			value = -EIOCBQUEUED;
>   	return value;
>   }
> 
> diff -uprN -X linux-2.6.20-aio21/Documentation/dontdiff 
> linux-2.6.20-aio21/fs/ocfs2/dlmglue.c linux-2.6.20-aio22/fs/ocfs2/dlmglue.c
> --- linux-2.6.20-aio21/fs/ocfs2/dlmglue.c	2007-03-04 21:45:52.000000000 
> +0300
> +++ linux-2.6.20-aio22/fs/ocfs2/dlmglue.c	2007-03-04 22:57:50.000000000 
> +0300
> @@ -1639,7 +1639,7 @@ int ocfs2_meta_lock_full(struct inode *i
> 
>   	status = ocfs2_cluster_lock(osb, lockres, level, dlm_flags, arg_flags);
>   	if (status < 0) {
> -		if (status != -EAGAIN && status != -EIOCBRETRY)
> +		if (status != -EAGAIN)
>   			mlog_errno(status);
>   		goto bail;
>   	}
> diff -uprN -X linux-2.6.20-aio21/Documentation/dontdiff 
> linux-2.6.20-aio21/include/linux/aio.h 
> linux-2.6.20-aio22/include/linux/aio.h
> --- linux-2.6.20-aio21/include/linux/aio.h	2007-03-04 21:46:45.000000000 
> +0300
> +++ linux-2.6.20-aio22/include/linux/aio.h	2007-03-04 22:57:50.000000000 
> +0300
> @@ -79,15 +79,6 @@ struct kioctx;
>    * not ask the method again -- ki_retry must ensure forward progress.
>    * aio_complete() must be called once and only once in the future, 
> multiple
>    * calls may result in undefined behaviour.
> - *
> - * If ki_retry returns -EIOCBRETRY it has made a promise that kick_iocb()
> - * will be called on the kiocb pointer in the future.  This may happen
> - * through generic helpers that associate kiocb->ki_wait with a wait
> - * queue head that ki_retry uses via current->io_wait.  It can also happen
> - * with custom tracking and manual calls to kick_iocb(), though that is
> - * discouraged.  In either case, kick_iocb() must be called once and only
> - * once.  ki_retry must ensure forward progress, the AIO core will wait
> - * indefinitely for kick_iocb() to be called.
>    */
>   struct kiocb {
>   	struct list_head	ki_run_list;
> diff -uprN -X linux-2.6.20-aio21/Documentation/dontdiff 
> linux-2.6.20-aio21/include/linux/errno.h 
> linux-2.6.20-aio22/include/linux/errno.h
> --- linux-2.6.20-aio21/include/linux/errno.h	2007-03-04 
> 21:45:51.000000000 +0300
> +++ linux-2.6.20-aio22/include/linux/errno.h	2007-03-04 
> 22:57:50.000000000 +0300
> @@ -22,7 +22,6 @@
>   #define EBADTYPE	527	/* Type not supported by server */
>   #define EJUKEBOX	528	/* Request initiated, but will not complete 
> before timeout */
>   #define EIOCBQUEUED	529	/* iocb queued, will get completion event */
> -#define EIOCBRETRY	530	/* iocb queued, will trigger a retry */
> 
>   #endif

Where is kiocbSetPgBusy() defined, and where in the documentation is it 
explained?  For that matter, what is the reason for changing the return 
value at all?

And if you are going to change, why not make the return value something
more logical?  For instance, return 0 to indicate the iocb is complete and
-EINPROGRESS to indicate another kick will occur.

Alan Stern

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