Re: Possible dcache BUG

[Marcelo Tosatti <marcelo.tosatti@cyclades.com>]

On Thu, Aug 19, 2004 at 10:38:19PM -0400, Gene Heskett wrote:
> On Thursday 19 August 2004 14:36, Marcelo Tosatti wrote:
> >Gene,
> >
> >That is:
> >
> >/*
> > * The buffer's backing address_space's private_lock must be held
> > */
> >static inline void __remove_assoc_queue(struct buffer_head *bh)
> >{
> >        BUG_ON(bh->b_assoc_buffers.next == NULL); 			<----------
> >        BUG_ON(bh->b_assoc_buffers.prev == NULL);
> >        list_del_init(&bh->b_assoc_buffers);
> >}
> >
> >Viro, Linus, Andrew, dont you have any idea what could cause such
> > mapping->b_assoc_mapping corruption?
> >
> >I can't see how that could be caused by flaky hardware.
> 
> There is still that possibility Marcelo.  Someone recommended I get 
> cpuburn and memburn, and before fixing the scanf statement (it was 
> broken) in memburn, I had compiled it for a 512 meg test the first 
> time, and a 768 meg test the next couple of runs.
> 
> All exited with errors like this:
> Passed round 133, elapsed 4827.19.
> FAILED at round 134/14208927: got ff00, expected 0!!!
> 
> REREAD: ff00, ff00, ff00!!!
> 
> [root@coyote memburn]# vim memburn.c
> [root@coyote memburn]# gcc -o memburn memburn.c
> [root@coyote memburn]# ./memburn
> Starting test with size 768 megs..
> 
> Passed round 0, elapsed 44.36.
> Passed round 1, elapsed 74.13.
> Passed round 2, elapsed 105.12.
> FAILED at round 3/25777183: got 2b00, expected 0!!!
> 
> REREAD: 2b00, 2b00, 2b00!!!
> 
> I've now rebuilt it with a better printf format string, and its 
> running over 768 megs again.  But this time the round counter is up 
> to 90 and still going...
> 
> Interesting too is that memburn has now allocated a 768 meg wide block 
> 5 times, and still no Oops.  Over a hundred megs in swap, but its 
> still running.
> 
> I lost the BUG_ON patches in fs/buffer.c, this is now 2.6.8.1-mm2 (but 
> I can go back if this fails of course)
> 
> Or can I just copy that 2.6.8-rc4/fs/buffer.c file over this one?

You can just copy it, _I think_. If you have problems just add the BUG_ON's by hand. 

Now Ingo also hit the same problem, Ingo can you reproduce that 
remove_inode_buffers()?