Re: negative dentry_stat.nr_unused causes aggressive dcache pruning

[Steve Lord <lord@xfs.org>]

Andrew Morton wrote:
> Steve Lord <lord@xfs.org> wrote:
> 
>>I have seen this stat go negative (just from booting up a multi cpu box),
>> and looking at the code, it is manipulated without locking in a number
>> of places. I have only seen this in real life on a 2.4 kernel, but 2.6
>> also looks vulnerable.
> 
> 
> In 2.6, both dentry_stat.nr_unused and dentry_stat.nr_dentry are covered
> by dcache_lock.  I just double-checked and all seems well.
> 

Looked again, you are right, looks like a 2.4 only problem and even there I
am darned if I can see how it leaks now, still digging as to where it is coming
from. I have a box which goes negative shortly after bootup, this seems to put
it in a feedback loop and  it just keeps heading south from there pushing on the
dcache. This is running on a fedora legacy kernel for redhat 9.0 which I added
kdb to. Starting to wonder if the compiler screwed up somewhere. I have an
external fiberchannel driver loaded, but it does not have any dentry related
code in it.

Steve