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    SubjectRe: [GIT PULL] block/io bits for 2.6.35-rc
    On 10/06/10 12:44 PM, Brian Bloniarz wrote:
    > On 06/10/2010 12:25 PM, Jens Axboe wrote:
    >> On 2010-06-10 17:55, Linus Torvalds wrote:
    >>> On Thu, Jun 10, 2010 at 6:44 AM, Jens Axboe<> wrote:
    >>>> - A set of patches fixing the WB_SYNC_NONE writeback from Christoph. So
    >>>> we should finally have both functional and working WB_SYNC_NONE from
    >>>> umount context.
    >>> I _really_ think this is too late, considering how broken it has been.
    >>> We already reverted the WB_SYNC_NONE things exactly because it didn't
    >>> work, didn't we? I'm going to be off-line in two days, and this part
    >>> of the pull request really makes me nervous, if only simply because of
    >>> the history of it all (ie it's always been broken, why shouldn't it be
    >>> broken now?).
    >>> IOW, that's a lot of scary changes, that have historically not been
    >>> safe or sufficiently tested, and have caused problems for various
    >>> filesystems. Convince me why they should suddenly be ok to merge?
    >> I agree, it's late and it makes me nervous too. I had them cook for
    >> a day, didn't see any problems. And Christoph would not send it in
    >> unless it passes at least xfs qa, which is what found the problems
    >> last time (the ones we reverted).
    >> It's fixing a regression where umount takes a LONG time if you have
    >> a lot of dirty inodes, since it basically degenerates to a data
    >> integrity writeback instead of a simple WB_SYNC_NONE. If it wasn't
    >> fixing a nasty regression (the distros are all wanting a real fix
    >> for this, it's a user problem), I would not be submitting this code
    >> at this point in time.
    > Reinforcing that last point: from what I could figure out, Fedora 13
    > is shipping the buggy WB_SYNC_NONE patch currently. Ubuntu 10.04 is
    > shipping an in-kernel workaround that has serious performance
    > drawbacks.
    > has links to the
    > downstream bugs.

    Jens, this bug has been biting my servers badly here for the past
    few months -- umount after a backup (from ext4 to ext4) takes 3-4 minutes
    instead of the expected 3-4 seconds.

    Is there a patch file for this against 2.6.34 that I (and others) could use?


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