Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH 2.6.19 5/5] fs: freeze_bdev with semaphore not mutex | Date | Thu, 9 Nov 2006 20:59:47 +0100 |
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Hi,
On Thursday, 9 November 2006 17:00, Pavel Machek wrote: > Hi! > > > > > Well, it looks like the interactions with dm add quite a bit of > > > > complexity here. > > > > > > What about just fixing xfs (thou shall not write to disk when kernel > > > threads are frozen), and getting rid of blockdev freezing? > > > > Well, first I must admit you were absolutely right being suspicious with > > respect to this stuff. > > (OTOH your patch found real bugs in suspend.c, so...) > > > OTOH I have no idea _how_ we can tell xfs that the processes have been > > frozen. Should we introduce a global flag for that or something? > > I guess XFS should just do all the writes from process context, and > refuse any writing when its threads are frozen... I actually still > believe it is doing the right thing, because you can't really write to > disk from timer.
This is from a work queue, so in fact from a process context, but from a process that is running with PF_NOFREEZE.
And I don't think we can forbid filesystems to use work queues. IMO it's a legitimate thing to do for an fs.
_But_.
Alasdair, do I think correctly that if there's a suspended device-mapper device below an non-frozen filesystem, then sys_sync() would block just as well as freeze_bdev() on this filesystem?
Rafael
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