From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52068) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Um2Y4-0002BH-IB for qemu-devel@nongnu.org; Mon, 10 Jun 2013 09:54:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Um2Y1-0007Wh-KS for qemu-devel@nongnu.org; Mon, 10 Jun 2013 09:54:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41946) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Um2Y1-0007WU-BD for qemu-devel@nongnu.org; Mon, 10 Jun 2013 09:54:13 -0400 Date: Mon, 10 Jun 2013 15:54:10 +0200 From: Kevin Wolf Message-ID: <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130610092122.2d683638@redhat.com> 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: Luiz Capitulino Cc: Stefan Hajnoczi , qemu-devel@nongnu.org, armbru@redhat.com 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'". The _real_ solution, of course, is to make bdrv_prepare_reopen() a void function and always set errp when something goes wrong. Kevin