Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 12 Jun 2003 17:26:27 +0100 | From | viro@parcelfa ... | Subject | Re: [PATCH] First casuality of hlist poisoning in 2.5.70 |
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On Wed, Jun 11, 2003 at 10:22:25PM -0700, Linus Torvalds wrote:
> HOWEVER, I actually suspect that the target really _cannot_ be unhashed, > and that the test makes no sense, and the sequence should just be > > /* Rehash the dentry onto the same hash as the target */ > hlist_del_rcu(&dentry->d_hash); > hlist_add_head_rcu(&dentry->d_hash, target->d_bucket); > dentry->d_vfs_flags &= ~DCACHE_UNHASHED;
> But I suspect that neither dentry nor target should really ever be > unhashed by the time we call d_move(). That's reinforced by the fact that > it looks like a unhashed dentry in d_move() would have been a silent bug > previously - staying unhashed if it just shared the bucket.
> Al, I'll be really happy having you go over this code too. And whatever we > decide is right (enforcing hashedness or whatever), we should assert it, > because clearly d_move() has been a bit too subtle for us so far.
Sigh... The real problem is not in d_move(), but in the way NFS drops dentries. That, and the fact that we are eating the consequences of RCU use in dcache - it had predictably made the entire thing _far_ too subtle.
We probably should accept that both d_move() arguments can be unhashed. After the move hashed status of source should remain as it is and victim^Wtarget should get unhashed.
We _do_ need to sort out the situation with unhashing stuff in NFS - in particular, the way it deals with mountpoints and with directories is a mess. I'm looking through that code, but it's bloody slow analysis due to RCU. Premature optimizations and all such... - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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