linux-kernel - Re: [PATCH vfs 1/2] lib: implement ptrset

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Message-ID: <20141118171628.GA434@htj.dyndns.org>
Date:	Tue, 18 Nov 2014 12:16:28 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Azat Khuzhin <a3at.mail@...il.com>
Cc:	Jens Axboe <axboe@...nel.dk>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@...radead.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH vfs 1/2] lib: implement ptrset

Hello,

On Tue, Nov 18, 2014 at 06:56:29PM +0300, Azat Khuzhin wrote:
> On Thu, Nov 13, 2014 at 05:09:27PM -0500, Tejun Heo wrote:
> > +int ptrset_add(void *ptr, struct ptrset *set, gfp_t gfp)
> > +{
> > +	struct ptrset_elem *elem;
> > +	struct rb_node *parent, **slot;
> > +
> > +	elem = kmalloc(sizeof(*elem), gfp);
> > +	if (!elem && !in_interrupt())	/* see ptrset_preload() */
> > +		elem = this_cpu_xchg(ptrset_preload_elem, NULL);
> > +	if (!elem)
> > +		return -ENOMEM;
> > +	elem->ptr = ptr;
> > +
> > +	if (ptrset_find_slot(elem->ptr, set, &slot, &parent)) {
> > +		kfree(elem);
> > +		return -EEXIST;
> > +	}
> 
> Maybe allocation *after* ptrset_find_slot() will be better?
> This will avoid extra kmalloc/kfree if such ptr already exist (and also
> will avoid ENOMEM for such cases).

Sure thing.  Will post an updated version soon.

Thanks.

-- 
tejun
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