Re: Highly reflinked and fragmented considered harmful?

Chris Dunlop
2022-05-11T02:17:03Z

On Wed, May 11, 2022 at 11:36:54AM +1000, Dave Chinner wrote:
> I think that's the thing that some people have missed in in this
> thread - I've know for a while now the scope of problems blocking
> flushes from statfs() can cause - any issue with background
> inodegc not making progress can deadlock the filesystem. I've lost
> count of the number of times I had inodegc go wrong or crash and the
> only possible recovery was to power cycle because nothing could be
> executed from the command line.
>
> That's because statfs() appears to be used in some commonly used
> library function and so many utility programs on the system will get
> stuck and be unable to run when inodegc dies, deadlocks, or takes a
> real long time to make progress.
>
> Hence I didn't need to do any analysis of Chris' system to know
> exactly what was going on - I've seen it many, many times myself and
> have work in progress that avoids those issues with inodegc work
> that never completes.
>
> IOWs, everything is understood, fixes are already written, and
> there's no actual threat of data loss or corruption from this issue.
> It's just lots of stuff getting stuck behind a long running
> operation...

Your patches are stuck behind other long running priorities, or the
patches address an issue of stuff getting stuck? Or, of course, both? ;-)

Out of interest, would this work also reduce the time spent mounting in my
case? I.e. would a lot of the work from my recovery mount be punted off
to a background thread?

Cheers,

Chris