linux-kernel - RE: [PATCH] aio: fix kernel bug when page is temporally busy

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Date:	Fri, 16 Feb 2007 00:06:31 +0300
From:	"Ananiev, Leonid I" <leonid.i.ananiev@...el.com>
To:	"Zach Brown" <zach.brown@...cle.com>
Cc:	"Ken Chen" <kenchen@...gle.com>, <suparna@...ibm.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	<linux-kernel@...r.kernel.org>, "linux-aio" <linux-aio@...ck.org>,
	"Chris Mason" <chris.mason@...cle.com>
Subject: RE: [PATCH] aio: fix kernel bug when page is temporally busy



-----Original Message-----
From: Zach Brown [mailto:zach.brown@...cle.com] 
Sent: Thursday, February 15, 2007 10:23 PM
To: Ananiev, Leonid I
Cc: Ken Chen; suparna@...ibm.com; Andrew Morton;
linux-kernel@...r.kernel.org; linux-aio; Chris Mason
Subject: Re: [PATCH] aio: fix kernel bug when page is temporally busy


On Feb 15, 2007, at 11:11 AM, Ananiev, Leonid I wrote:

>> It returns -EIOCBRETRY without guaranteeing that kick_iocb() will be
>> called.  This can lead to operations hanging
>
> If EIOCBRETRY then generic_file_aio_write() will be recalled for the
> same iocb.

Only if kick_iocb() is called.  It won't be called if i_i_p2_r() was  
the only thing to return -EIOCBRETRY.

>
>> It overwrites -EIOCBQUEUED, leading to an aio_complete() while a
>> retry is happening.
>
> EIOCBQUEUED or EIOCBRETRY does not lead to aio_complete() call:

Not by fs/aio.c, but *by the place that originated -EIOCBQUEUED*.   
Later.  After IO has completed.  see fs/direct-io.c:dio_bio_end_aio().

This is what -EIOCBQUEUED means!  It's a promise to call aio_complete 
() in the future.

Have you read the giant comment over the definition of struct kiocb  
in include/linux/aio.h?

>> This can lead to reference count confusion.
> But just reference count confusion was deleted by patch. Isn't it?

Sorry, I don't understand what you're trying to ask here.

- z
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