Messages in this thread |  | | | From | "Rafael J. Wysocki" <> | | Subject | Re: [PATCH] Freeze bdevs when freezing processes. | | Date | Fri, 27 Oct 2006 16:37:21 +0200 |
| |
On Friday, 27 October 2006 03:38, David Chinner wrote: > On Thu, Oct 26, 2006 at 11:11:29AM +0200, Rafael J. Wysocki wrote: > > On Thursday, 26 October 2006 10:57, David Chinner wrote: > > > On Thu, Oct 26, 2006 at 06:18:29PM +1000, Nigel Cunningham wrote: > > > > As you have them at the moment, the threads seem to be freezing fine. > > > > The issue I've seen in the past related not to threads but to timer > > > > based activity. Admittedly it was 2.6.14 when I last looked at it, but > > > > there used to be a possibility for XFS to submit I/O from a timer when > > > > the threads are frozen but the bdev isn't frozen. Has that changed? > > > > > > I didn't think we've ever done that - periodic or delayed operations > > > are passed off to the kernel threads to execute. A stack trace > > > (if you still have it) would be really help here. > > > > > > Hmmm - we have a couple of per-cpu work queues as well that are > > > used on I/O completion and that can, in some circumstances, > > > trigger new transactions. If we are only flush metadata, then > > > I don't think that any more I/o will be issued, but I could be > > > wrong (maze of twisty passages). > > > > Well, I think this exactly is the problem, because worker_threads run with > > PF_NOFREEZE set (as I've just said in another message). > > Ok, so freezing the filesystem is the only way you can prevent > this as the workqueues are flushed as part of quiescing the filesystem.
Yes, I think so.
Now at last I know what the problem actually is and why we need the freezing of filesystems, so thanks for helping me understand that. :-)
Greetings, Rafael
-- You never change things by fighting the existing reality. R. Buckminster Fuller - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |