Re: dcache shrink list corruption?

[Szeredi Miklos]

On Fri, May 2, 2014 at 7:51 AM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> On Wed, Apr 30, 2014 at 11:15:15AM +0200, Miklos Szeredi wrote:

>> IBM is triggering this with the host01 test from the LTP suite.  I haven't yet
>> tried to reproduce it.
>
> Could you repost their report?  So far I hadn't managed to get actual list
> corruption on mainline kernel - it definitely is possible, but on all
> testcases so far the race window is too narrow.  So if they have a reproducer
> that doesn't take an insane amount of time, I'd really like to see it...

The only reproducer they have is LTP/host01, and can trigger the bug
reliably within hours.

The bug is private, but I'll ask if I can repost it.  The first thing
is a a warning from the D_FLAG_VERIFY() in d_shrink_del() from
shrink_dentry_list().  They added printks that show that the dentry
has DCACHE_DENTRY_KILLED.

We could ask for a dump, but this is the only rational explanation I
could find for this (and a shrink list with two dentries, with racing
dput on both nicely explains the case where the shrink list's prev
pointer still points to the already killed dentry).

Thanks,
Miklos
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/