Re: [PATCH 01/10] Fix idr_remove()

[Nadia Derbey]

Andrew Morton wrote:
> On Tue, 29 Apr 2008 16:33:05 +0200
> Nadia.Derbey@xxxxxxxx wrote:
>
>
> > [PATCH 01/10]
> >
> > This patch fixes idr_remove(): the return inside the loop makes us free only
> > a single layer.
> >
> > Signed-off-by: Nadia Derbey <Nadia.Derbey@xxxxxxxx>
> >
> > ---
> > lib/idr.c |    2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > Index: linux-2.6.25-mm1/lib/idr.c
> > ===================================================================
> > --- linux-2.6.25-mm1.orig/lib/idr.c	2008-04-25 15:29:00.000000000 +0200
> > +++ linux-2.6.25-mm1/lib/idr.c	2008-04-25 15:48:34.000000000 +0200
> > @@ -385,8 +385,8 @@ void idr_remove(struct idr *idp, int id)
> > 	while (idp->id_free_cnt >= IDR_FREE_MAX) {
> > 		p = alloc_layer(idp);
> > 		kmem_cache_free(idr_layer_cache, p);
> > -		return;
> > 	}
> > +	return;
> > }
> > EXPORT_SYMBOL(idr_remove);
>
>
> erk, ancient bug.
>
> I _think_ the implications of this are that an idr tree will grow fatter
> than it needs to be, but there is no permanent leak: idr_destroy() will
> still free everything, yes?

Yes, exactly. Actually, I've not checked whether all the kernel 
components call idr_destroy() when needed.

> And a consequence of the fix is that idr manipulations will now result in
> more allocs and frees,

Not necessarily more allocs: this loop keeps IDR_FREE_MAX layers in the 
free list. So idr_pre_get() should be a noop.

> but the amount of memory which a tree uses will be
> less?

Regards,
Nadia


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