Re: [PATCH] vfs: Fix, simpliy and stop using d_dname for the /proc/*/ns/* files.

[Ivan Delalande <colona@arista.com>]

On Sat, Jun 06, 2015 at 02:27:24PM -0500, Eric W. Biederman wrote:
> Ivan Delalande <colona@arista.com> writes:
> 
> > On Thu, May 21, 2015 at 12:23:25AM +0100, Al Viro wrote:
> >> On Wed, May 20, 2015 at 05:05:30PM -0500, Eric W. Biederman wrote:
> >> > -	dentry = d_alloc_pseudo(mnt->mnt_sb, &qname);
> >> > +	dentry = d_alloc_name(mnt->mnt_root, name);
> >> >  	if (!dentry) {
> >> >  		iput(inode);
> >> >  		mntput(mnt);
> >> >  		return ERR_PTR(-ENOMEM);
> >> >  	}
> >> > -	d_instantiate(dentry, inode);
> >> > +	d_add(dentry, inode);
> >> 
> >> Careful - that might have non-trivial effects.  Namely, you are making
> >> the root dentry of that sucker a contention point and adding to hash
> >> pollution...  It's probably not going to cause visible problems, but
> >> it's worth profiling just to be sure.
> >> 
> >> Besides, you are violating a bunch of rules here - several hashed
> >> children of the same directory with the same name all at once...
> >> not nice.
> >
> > Hey Eric, did you have any thought about Al’s concerns?
> 
> Massive difference in perspective for the most part.  It did cause me to
> step back and really look at what that code is doing and why.
> 
> For the immediate problem the issue is that the WARN_ON is warning about
> something nothing in the kernel has done for 5 years and in practice as
> you have seen is actually wrong.  So deleting the warning message
> appears the best way to handle the situation you are seeing.

Ok, great. Thanks for all the info and the new patch, Eric.

-- 
Ivan "Colona" Delalande
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