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

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Date:	Sat, 10 Feb 2007 21:27:46 +0300
From:	"Ananiev, Leonid I" <leonid.i.ananiev@...el.com>
To:	"Ken Chen" <kenchen@...gle.com>
Cc:	<suparna@...ibm.com>, "Andrew Morton" <akpm@...ux-foundation.org>,
	<linux-kernel@...r.kernel.org>, "linux-aio" <linux-aio@...ck.org>,
	"Zach Brown" <zach.brown@...cle.com>,
	"Chris Mason" <chris.mason@...cle.com>,
	"Badari Pulavarty" <pbadari@...ibm.com>
Subject: RE: [PATCH] aio: fix kernel bug when page is temporally busy

> If invalidate_inode_pages2_range() says it can not invalidate pages,
> while dio to the same file offset range is in flight, something is
> really wrong there.

If invalidate_inode_pages2_range() says it can not invalidate pages
It means that soft_irq does completing now on other cpu.
Next retry() will see a IO well completed.
Leonid

-----Original Message-----
From: Ken Chen [mailto:kenchen@...gle.com] 
Sent: Saturday, February 10, 2007 9:05 PM
To: Ananiev, Leonid I
Cc: suparna@...ibm.com; Andrew Morton; linux-kernel@...r.kernel.org;
linux-aio; Zach Brown; Chris Mason; Badari Pulavarty
Subject: Re: [PATCH] aio: fix kernel bug when page is temporally busy

On 2/9/07, Ananiev, Leonid I <leonid.i.ananiev@...el.com> wrote:
> I have used EIOCBRETRY in the patch to minimize source code
modification
> only.
> [...]
> A lot of errno's have different meaning in different functions or
> contexts. EAGAIN could be used instated of EIOCBRETRY for irredundant
> set.

I also think the original patch is wrong.  It might shut up kernel
panic by eliminate double calls to aio_complete(), but it will
silently introduce data corruption.

If invalidate_inode_pages2_range() says it can not invalidate pages,
while dio to the same file offset range is in flight, something is
really wrong there.  In generic_file_direct_IO, the function
explicitly flushes all dirty pages and wait on them before submits
DIO.

So any error value returned from invalidate_inode_pages2_range() has
to be taken seriously in the direct IO submit path instead of dropping
it to the floor.

- Ken
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