From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50371) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fM6A5-0005If-PM for qemu-devel@nongnu.org; Fri, 25 May 2018 02:25:14 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fM6A4-00074P-OW for qemu-devel@nongnu.org; Fri, 25 May 2018 02:25:13 -0400 Date: Fri, 25 May 2018 14:25:03 +0800 From: Fam Zheng Message-ID: <20180525062503.GE28589@lemon.usersys.redhat.com> References: <20180521063516.5479-1-famz@redhat.com> <677208b5-586b-354a-5fd4-67468152510e@redhat.com> <20180525021641.GD12594@lemon.usersys.redhat.com> <87a7soxp5j.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87a7soxp5j.fsf@dusky.pond.sub.org> Subject: Re: [Qemu-devel] [PATCH] nvme: Make nvme_init error handling code more readable List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: Paolo Bonzini , Kevin Wolf , qemu-devel@nongnu.org, qemu-block@nongnu.org, Max Reitz On Fri, 05/25 07:47, Markus Armbruster wrote: > Fam Zheng writes: > > > On Thu, 05/24 19:16, Paolo Bonzini wrote: > >> On 21/05/2018 08:35, Fam Zheng wrote: > >> > Coverity doesn't like the tests under fail label (report CID 1385847). > >> > Reset the fields so the clean up order is more apparent. > >> > > >> > Signed-off-by: Fam Zheng > >> > --- > >> > block/nvme.c | 7 +++++++ > >> > 1 file changed, 7 insertions(+) > >> > > >> > diff --git a/block/nvme.c b/block/nvme.c > >> > index 6f71122bf5..8239b920c8 100644 > >> > --- a/block/nvme.c > >> > +++ b/block/nvme.c > >> > @@ -560,6 +560,13 @@ static int nvme_init(BlockDriverState *bs, const char *device, int namespace, > >> > qemu_co_queue_init(&s->dma_flush_queue); > >> > s->nsid = namespace; > >> > s->aio_context = bdrv_get_aio_context(bs); > >> > + > >> > + /* Fields we've not touched should be zero-initialized by block layer > >> > + * already, but reset them anyway to make the error handling code easier to > >> > + * reason. */ > >> > + s->regs = NULL; > >> > + s->vfio = NULL; > >> > + > >> > ret = event_notifier_init(&s->irq_notifier, 0); > >> > if (ret) { > >> > error_setg(errp, "Failed to init event notifier"); > >> > > >> > >> I think we should just mark it as a false positive or do something like > >> > >> fail_regs: > >> qemu_vfio_pci_unmap_bar(s->vfio, 0, (void *)s->regs, 0, NVME_BAR_SIZE); > >> fail_vfio: > >> qemu_vfio_close(s->vfio); > >> fail: > >> g_free(s->queues); > >> event_notifier_cleanup(&s->irq_notifier); > >> return ret; > >> > >> even though it's a larger patch. > > > > And that makes five labels in total, I'm not sure I like it: > > > > fail_handler: > > aio_set_event_notifier(bdrv_get_aio_context(bs), &s->irq_notifier, > > false, NULL, NULL); > > fail_queue: > > nvme_free_queue_pair(bs, s->queues[0]); > > fail_regs: > > qemu_vfio_pci_unmap_bar(s->vfio, 0, (void *)s->regs, 0, NVME_BAR_SIZE); > > fail_vfio: > > qemu_vfio_close(s->vfio); > > fail: > > g_free(s->queues); > > event_notifier_cleanup(&s->irq_notifier); > > return ret; > > Doesn't look materially worse to me :) The labels themselves are not ugly or bad, but the goto statements above will be harder to manage. > > With nice cleanup functions that detect "hasn't been set up" and do > nothing then, like free(NULL), you can use just one label. Sadly, > cleanup functions are often not nice that way. nvme_free_queue_pair and qemu_vfio_close are cleanup functions and we can improve them, but to make qemu_vfio_pci_unmap_bar behave similarly is just odd: it's not a clean up function, at least not for s->vfio. Fam