From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julia Lawall Subject: Re: [PATCH 12/39] dm: drop null test before destroy functions Date: Mon, 14 Sep 2015 20:50:03 +0200 (CEST) Message-ID: References: <1442146532-9100-1-git-send-email-Julia.Lawall@lip6.fr> <1442146532-9100-13-git-send-email-Julia.Lawall@lip6.fr> <20150914140040.GA11815@redhat.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Mikulas Patocka Cc: Mike Snitzer , device-mapper development , Alasdair Kergon , kernel-janitors@vger.kernel.org, Neil Brown , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, sergey.senozhatsky@gmail.com List-Id: linux-raid.ids On Mon, 14 Sep 2015, Mikulas Patocka wrote: > > > On Mon, 14 Sep 2015, Mike Snitzer wrote: > > > On Mon, Sep 14 2015 at 9:46am -0400, > > Mikulas Patocka wrote: > > > > > > > > > > > On Sun, 13 Sep 2015, Julia Lawall wrote: > > > > > > > Remove unneeded NULL test. > > > > > > > > The semantic patch that makes this change is as follows: > > > > (http://coccinelle.lip6.fr/) > > > > > > > > // > > > > @@ expression x; @@ > > > > -if (x != NULL) > > > > \(kmem_cache_destroy\|mempool_destroy\|dma_pool_destroy\)(x); > > > > // > > > > > > > > Signed-off-by: Julia Lawall > > > > > > > > --- > > > > drivers/md/dm-bufio.c | 3 +-- > > > > drivers/md/dm-cache-target.c | 3 +-- > > > > drivers/md/dm-crypt.c | 6 ++---- > > > > drivers/md/dm-io.c | 3 +-- > > > > drivers/md/dm-log-userspace-base.c | 3 +-- > > > > drivers/md/dm-region-hash.c | 4 +--- > > > > drivers/md/dm.c | 13 ++++--------- > > > > 7 files changed, 11 insertions(+), 24 deletions(-) > > > > > > > > diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c > > > > index 83cc52e..8ad39b6 100644 > > > > --- a/drivers/md/dm-bufio.c > > > > +++ b/drivers/md/dm-bufio.c > > > > @@ -1864,8 +1864,7 @@ static void __exit dm_bufio_exit(void) > > > > for (i = 0; i < ARRAY_SIZE(dm_bufio_caches); i++) { > > > > struct kmem_cache *kc = dm_bufio_caches[i]; > > > > > > > > - if (kc) > > > > - kmem_cache_destroy(kc); > > > > + kmem_cache_destroy(kc); > > > > } > > > > > > The variable here can be NULL. I don't know how did you conclude that it > > > cannot. It seems that you didn't test the patch, if you did, you'd hit > > > NULL pointer dereference here. > > > > kmem_cache_destroy(), mempool_destroy(), etc all check for NULL and just > > return. So there is no need for the callers to check for NULL too. > > > > Mike > > I see. It was recent change that I missed. The relevant commits were in the cover letter: kmem_cache_destroy (commit 3942d29918522) mempool_destroy (commit 4e3ca3e033d1) dma_pool_destroy (commit 44d7175da6ea) julia