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    SubjectRe: [xfs-masters] Re: freeze vs freezer
    On Mon, Jun 30, 2008 at 01:22:47AM +0200, Rafael J. Wysocki wrote:
    > On Monday, 30 of June 2008, Dave Chinner wrote:
    > > On Thu, Jun 26, 2008 at 05:09:10PM +0200, Pavel Machek wrote:
    > > > > > Is this the same thing the per-device IO-queue-freeze patches for
    > > > > >HDAPS also
    > > > > > need to do? If so, you may want to talk to Elias Oltmanns
    > > > > > <eo@nebensachen.de> about it. Added to CC.
    > > > >
    > > > > Thanks for the heads up Henrique. Even though these issues seem to be
    > > > > related up to a certain degree, there probably are some important
    > > > > differences. When suspending a system, the emphasis is on leaving the
    > > > > system in a consistent state (think of journalled file systems), whereas
    > > > > disk shock protection is mainly concerned with stopping I/O as soon as
    > > > > possible. As yet, I cannot possibly say to what extend these two
    > > > > concepts can be reconciled in the sense of sharing some common code.
    > > >
    > > > Actually, I believe requirements are same.
    > > >
    > > > 'don't do i/o in dangerous period'.
    > > >
    > > > swsusp will just do sync() before entering dangerous period. That
    > > > provides consistent-enough state...
    > >
    > > As I've said many times before - if the requirement is "don't do
    > > I/O" then you have to freeze the filesystem. In no way does 'sync'
    > > prevent filesystems from doing I/O.....
    >
    > Well, it seems we can handle this on the block layer level, by temporarily
    > replacing the elevator with something that will selectively prevent fs I/O
    > from reaching the layers below it.

    Why? What part of freeze_bdev() doesn't work for you?

    Cheers,

    Dave.
    --
    Dave Chinner
    david@fromorbit.com


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