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    SubjectRe: [RFC] ext3 freeze feature
    On Sat, Jan 26, 2008 at 04:35:26PM +1100, David Chinner wrote:
    > On Fri, Jan 25, 2008 at 07:59:38PM +0900, Takashi Sato wrote:
    > > The points of the implementation are followings.
    > > - Add calls of the freeze function (freeze_bdev) and
    > > the unfreeze function (thaw_bdev) in ext3_ioctl().
    > >
    > > - ext3_freeze_timeout() which calls the unfreeze function (thaw_bdev)
    > > is registered to the delayed work queue to unfreeze the filesystem
    > > automatically after the lapse of the specified time.
    >
    > Seems like pointless complexity to me - what happens if a
    > timeout occurs while the filsystem is still freezing?
    >
    > It's not uncommon for a freeze to take minutes if memory
    > is full of dirty data that needs to be flushed out, esp. if
    > dm-snap is doing COWs for every write issued....

    Sorry, ignore this bit - I just realised the timer is set
    up after the freeze has occurred....

    Still, that makes it potentially dangerous to whatever is being
    done while the filesystem is frozen....

    Cheers,

    Dave.
    --
    Dave Chinner
    Principal Engineer
    SGI Australian Software Group


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