Re: xfs leaking?

[Dave Chinner <david@fromorbit.com>]

On Fri, Jul 11, 2008 at 12:04:10PM -0500, Eric Sandeen wrote:
> after my  fill-the-1T-fs-with-20k-files test I tried an xfs_repair, and
> it was sorrowfully slow compared to e2fsck of ext4 - I stopped it after
> almost 2 hours, and only half complete.
> 
> I noticed that during the run, I was about out of memory (8G) and
> swapping badly.
> 
> So I unmounted the fs, dropped caches, and was astounded to find
> 10492540 buffer heads still in the slab caches.

Curious - that implies buffer heads aren't being freed. But
if the pages have been freed, then the bufferheads should have
been. Generic code or VM bug perhaps?

> This was all  on 2.6.26-rc2 (I need to update) and lazy-count=1, 1T fs,
> 32 ags, mounted with inode64, nobarriers, and maximal logbuf count & size.
> 
> Rebooted, let the fs_mark test run just a bit, then tried removing the
> xfs module because I forgot to load the one with dave's  fix, and:
> 
> slab error in kmem_cache_destroy(): cache `xfs_inode': Can't free all objects
> Pid: 3676, comm: rmmod Not tainted 2.6.26-rc2 #3
> 
> Call Trace:
>  [<ffffffff80287e18>] kmem_cache_destroy+0x7d/0xb9
>  [<ffffffffa03e6708>] :xfs:xfs_cleanup+0x5c/0xf9
>  [<ffffffffa03e67bf>] :xfs:exit_xfs_fs+0x1a/0x28
>  [<ffffffff80250b1f>] sys_delete_module+0x186/0x1de
>  [<ffffffff8020bee2>] tracesys+0xd5/0xda

....

That's rather unhealthy. I'm running a 2.6.26-rc9-git? on
my uml system, and when no filesystems are mounted all the XFS
slab caches have zero objects in them, even after several runs
on xfsqa. So I don't see any obvious leak here. You did unmount
the filesystem(s) first, right?

I'd suggest updating to 2.6.26-rc9 and repeating the test.  After
unmounting all the filesystems and before you rmmod the kernel
module, dump /proc/slabinfo so we can see if there are remaining
objects in the XFs slabs....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com