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    SubjectRE: [PATCH] aio: fix kernel bug when page is temporally busy
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    > 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.

    > It overwrites -EIOCBQUEUED, leading to an aio_complete() while a
    > retry is happening.

    EIOCBQUEUED or EIOCBRETRY does not lead to aio_complete() call:
    if (ret != -EIOCBRETRY && ret != -EIOCBQUEUED) {
    aio_complete(iocb, ret, 0);

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

    Leonid

    -----Original Message-----
    From: Zach Brown [mailto:zach.brown@oracle.com]
    Sent: Thursday, February 15, 2007 9:25 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

    > If invalidate_inode_pages2_range() will return EIOCBRETRY as the patch
    > "aio: fix kernel bug when page is temporally busy"

    Sorry Leonid, this patch is not safe.

    It returns -EIOCBRETRY without guaranteeing that kick_iocb() will be
    called. This can lead to operations hanging, both AIO and calls that
    come through do_sync_{read,write}.

    It overwrites -EIOCBQUEUED, leading to an aio_complete() while a
    retry is happening. This can lead to reference count confusion.
    Double-frees, referencing freed memory, that kind of thing. This
    isn't a new problem. The current code that overwrites with -EIO has
    this problem. But moving to -EIOCBRETRY does introduce new behaviour
    of aio_complete() and the retry path racing.

    I'll have a candidate patch to address the problem of EIO being
    raised on the way back up from a path which has returned -EIOCBQUEUED.

    - z
    -
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