From: Andrew Morton <akpm@linux-foundation.org>
To: Roland Dreier <roland@kernel.org>
Cc: Joern Engel <joern@logfs.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] btree: Fix tree corruption in btree_get_prev()
Date: Wed, 6 Jun 2012 18:29:38 -0700 [thread overview]
Message-ID: <20120606182938.f8f6178d.akpm@linux-foundation.org> (raw)
In-Reply-To: <CAG4TOxNwVYPPP_AL=YZ6LnZZWyp8FUa50aGtgqGjTwnu598-Lw@mail.gmail.com>
On Wed, 6 Jun 2012 17:44:20 -0700 Roland Dreier <roland@kernel.org> wrote:
> On Wed, Jun 6, 2012 at 4:36 PM, Roland Dreier <roland@kernel.org> wrote:
> > On the other hand, your change makes me think we don't
> > even need a separate iterator (and we can avoid the variable
> > length array declaration)
>
> FWIW with that change on top of my patch, I see
>
> add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-123 (-123)
> function old new delta
> btree_get_prev 646 523 -123
>
> on x86-64, so avoiding the variable length array is definitely
> worth something.
>
> So the issue for me is whether messing with the caller's
> __key storage is OK, or if it's worth having a temporary
> local variable.
>
Sometimes altering the caller's *__key when lookup fails is pretty rude
behavior :(
Perhaps we could add an arg to btree_get_prev(), provide it with
separate input and output key pointers?
prev parent reply other threads:[~2012-06-07 1:29 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-06 17:17 [PATCH 1/2] btree: Fix tree corruption in btree_get_prev() Roland Dreier
2012-06-06 17:17 ` [PATCH 2/2] btree: Catch NULL value before it does harm Roland Dreier
2012-06-06 23:21 ` [PATCH 1/2] btree: Fix tree corruption in btree_get_prev() Andrew Morton
2012-06-06 23:36 ` Roland Dreier
2012-06-07 0:44 ` Roland Dreier
2012-06-07 1:29 ` Andrew Morton [this message]
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