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Date: Tue, 27 Oct 2009 20:38:10 +0300 (MSK)
From: malc <av1474@comtv.ru>
Subject: Re: [Qemu-devel] [PATCH] Improve error reporting on file access
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References: <20091001144256.GA30845@linuxtx.org>
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To: Markus Armbruster <armbru@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>, "Justin M. Forbes" <jmforbes@linuxtx.org>, qemu-devel@nongnu.org

On Tue, 27 Oct 2009, Markus Armbruster wrote:

> Mark McLoughlin <markmc@redhat.com> writes:
> 
> > On Thu, 2009-10-01 at 09:42 -0500, Justin M. Forbes wrote:
> >> Author: Justin M. Forbes <jforbes@redhat.com>
> >> Date:   Thu Oct 1 09:34:56 2009 -0500
> >> 
> >>     Improve error reporting on file access
> >>     
> >>     By making the error reporting include strerror(errno), it gives the user
> >>     a bit more indication as to why qemu failed.  This is particularly
> >>     important for people running qemu as a non root user.
> >>     
> >>     Signed-off-by: Justin M. Forbes <jforbes@redhat.com>
> >
> > Certainly looks sensible to me
> >
> > Not having this is hurting us in Fedora 12 because we've started running
> > qemu as an unprivileged user and people are having a hard time figuring
> > out the various errors they're seeing caused by the change. This should
> > help them.
> >
> > Only concern is that errno might not be getting propagated correctly by
> > some of these functions, but we can fix that later if so.
> 
> Here's one:
> 
> diff --git a/vl.c b/vl.c
> index 7bfd415..70fd2ca 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2232,8 +2232,8 @@ DriveInfo *drive_init(QemuOpts *opts, void *opaque,
>      }
> 
>      if (bdrv_open2(dinfo->bdrv, file, bdrv_flags, drv) < 0) {
> -        fprintf(stderr, "qemu: could not open disk image %s\n",
> -                        file);
> +        fprintf(stderr, "qemu: could not open disk image %s: %s\n",
> +                        file, strerror(errno));
>          return NULL;
>      }
> 

bdrv_open2 is not guaranteed to use POSIX functions for it's file
manipulation, hence the patch is wrong.

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