From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55048) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Um2gX-0005tI-VI for qemu-devel@nongnu.org; Mon, 10 Jun 2013 10:03:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Um2gS-0002O3-7H for qemu-devel@nongnu.org; Mon, 10 Jun 2013 10:03:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53679) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Um2gR-0002Nu-UD for qemu-devel@nongnu.org; Mon, 10 Jun 2013 10:02:56 -0400 Date: Mon, 10 Jun 2013 10:02:52 -0400 From: Luiz Capitulino Message-ID: <20130610100252.139078b0@redhat.com> In-Reply-To: <20130610135410.GH3636@dhcp-200-207.str.redhat.com> References: <1370634755-18132-1-git-send-email-lcapitulino@redhat.com> <1370634755-18132-4-git-send-email-lcapitulino@redhat.com> <20130610084347.GC5308@stefanha-thinkpad.redhat.com> <20130610092122.2d683638@redhat.com> <20130610135410.GH3636@dhcp-200-207.str.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 3/9] block: bdrv_reopen_prepare(): use error_setg_file_open() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: Stefan Hajnoczi , qemu-devel@nongnu.org, armbru@redhat.com On Mon, 10 Jun 2013 15:54:10 +0200 Kevin Wolf wrote: > Am 10.06.2013 um 15:21 hat Luiz Capitulino geschrieben: > > On Mon, 10 Jun 2013 10:43:47 +0200 > > Stefan Hajnoczi wrote: > > > > > On Fri, Jun 07, 2013 at 03:52:29PM -0400, Luiz Capitulino wrote: > > > > Signed-off-by: Luiz Capitulino > > > > --- > > > > block.c | 3 +-- > > > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > > > > > diff --git a/block.c b/block.c > > > > index 79ad33d..c78f152 100644 > > > > --- a/block.c > > > > +++ b/block.c > > > > @@ -1291,8 +1291,7 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue, > > > > if (local_err != NULL) { > > > > error_propagate(errp, local_err); > > > > } else { > > > > - error_set(errp, QERR_OPEN_FILE_FAILED, > > > > - reopen_state->bs->filename); > > > > + error_setg_file_open(errp, errno, reopen_state->bs->filename); > > > > > > Looking closer, my suggestion was wrong too. > > > > > > I think QERR_OPEN_FILE_FAILED is simply the wrong error here. We don't > > > know that the error occurred when trying to open a file. > > > > Right. > > > > > errno does not necessarily contain the error value! > > > > There are two ways to fix it (and they're not mutually exclusive): > > > > 1. We could review all bdrv_reopen_prepare() methods and make sure they > > set errno on failure > > > > 2. We set errno=0 before calling the bdrv_reopen_prepare() method and if > > there's an error and if errno != 0 we use it, otherwise we set a generic > > "failed to prepare to reopen image" error > > > > Option 1 goes a bit beyond the time I'd like to spent on this series. > > Option 2 is quite reasonable. > > > > What do you think? > > errno is definitely not reliable here and won't be. You must use -ret if > you want a meaningful error message. > > I think Stefan's point was more that "Could not open" might not be the > right message for a reopen, so we'd have to use error_setg_errno() > directly with a different message here, like "Could not prepare reopen > for '%s'". Ok, but Stefan also said that -ret is not reliable. And after quickly checking the code I see he's right, as there are methods that return -1. I think the safest thing to do is to have a generic error message for for this now and in the future we should propagate errp or return -errno.