On Thu, Oct 27, 2016 at 04:41:33PM +1100, Dave Chinner wrote:
> And that's indicative of a delalloc metadata reservation being
> being too small and so we're allocating unreserved blocks.
>
> Different symptoms, same underlying cause, I think.
>
> I see the latter assert from time to time in my testing, but it's
> not common (maybe once a month) and I've never been able to track it
> down. However, it doesn't affect production systems unless they hit
> ENOSPC hard enough that it causes the critical reserve pool to be
> exhausted iand so the allocation fails. That's extremely rare -
> usually takes a several hundred processes all trying to write as had
> as they can concurrently and to all slip through the ENOSPC
> detection without the correct metadata reservations and all require
> multiple metadata blocks to be allocated durign writeback...
>
> If you've got a way to trigger it quickly and reliably, that would
> be helpful...
Seems pretty quickly reproducable for me in some shape or form.
Run trinity with --enable-fds=testfile and create enough children
to create a fair bit of contention, (for me -C64 seems a good fit on
spinning rust, but if you're running on shiny nvme you might have to pump it up
a bit).
Dave
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