balance_dirty_pages broken

From: Doug Ledford (dledford@redhat.com)
Date: Wed Oct 16 2002 - 23:36:23 EST


Actually, I don't know if it's balance_dirty_pages fault or some other
part of the kernel's fault, but it is broken here. Failure mode is that
balance_dirty_pages would loop forever. Reason it would loop forever is
because the ps struct had a negative entry for nr_dirty. Breaking out of
the loop when ps.nr_dirty < 0 allows my machine to live. Now, *why*
ps.nr_dirty is < 0 is another issue. I have no clue. Well, I have one
clue, but no idea if it's valid or another red herring ;-) Machine only
has 256MB RAM, but has 4GB Highmem support enabled. Don't know if that
confuses the page counter stuff, having no actual highmem available.

If you need details about the machine, just ask. This was easy for me to
trigger by running mke2fs on a scsi disk. Would hit this every time.

-- 
  Doug Ledford <dledford@redhat.com>     919-754-3700 x44233
         Red Hat, Inc. 
         1801 Varsity Dr.
         Raleigh, NC 27606
  
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