Re: bio linked list corruption.

[Dave Jones]

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