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