Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [xfs-masters] Re: freeze vs freezer | Date | Mon, 30 Jun 2008 01:22:47 +0200 |
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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.
I talked with Jens about it on a very general level, but it seems doable at first sight.
Thanks, Rafael
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