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From: "Aneesh Kumar K. V" <aneesh.kumar@linux.vnet.ibm.com>
Subject: Re: [Qemu-devel] [PATCH -V3 4/8] hw/9pfs: Implement syncfs
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Date: Mon, 14 Mar 2011 00:29:56 +0530
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: aliguori@us.ibm.com, "Venkateswararao Jujjuri (JV)" <jvrao@linux.vnet.ibm.com>, qemu-devel@nongnu.org

On Sun, 13 Mar 2011 16:24:13 +0000, Stefan Hajnoczi <stefanha@gmail.com> wr=
ote:
> On Sat, Mar 5, 2011 at 5:52 PM, Aneesh Kumar K.V
> <aneesh.kumar@linux.vnet.ibm.com> wrote:
> > +static void v9fs_post_do_syncfs(V9fsState *s, V9fsPDU *pdu, int err)
> > +{
> > + =C2=A0 =C2=A0if (err =3D=3D -1) {
> > + =C2=A0 =C2=A0 =C2=A0 =C2=A0err =3D -errno;
> > + =C2=A0 =C2=A0}
>=20
> errno may have been clobbered by any standard library function/syscall
> invoked by this thread before v9fs_post_do_syncfs() was called.  Why
> not pass the -errno in the function argument?
>=20
> static void v9fs_post_do_syncfs(V9fsState *s, V9fsPDU *pdu, int err)
> {
>  =C2=A0 =C2=A0complete_pdu(s, pdu, err);
> }
>=20
> I strongly suggest doing a separate patch series to clean up of all of
> virtio-9p to stop using errno.  It's bad practice and I've caught
> several errno mistakes in the virtio-9p patches I've reviewed - I bet
> there are other instances lurking around.

Agreed.  I will look at the error handling more closely

>=20
> > +static void v9fs_syncfs(V9fsState *s, V9fsPDU *pdu)
> > +{
> > + =C2=A0 =C2=A0int err;
> > + =C2=A0 =C2=A0int32_t fid;
> > + =C2=A0 =C2=A0size_t offset =3D 7;
> > + =C2=A0 =C2=A0V9fsFidState *fidp;
> > +
> > + =C2=A0 =C2=A0pdu_unmarshal(pdu, offset, "d", &fid);
> > + =C2=A0 =C2=A0fidp =3D lookup_fid(s, fid);
> > + =C2=A0 =C2=A0if (fidp =3D=3D NULL) {
> > + =C2=A0 =C2=A0 =C2=A0 =C2=A0err =3D -ENOENT;
> > + =C2=A0 =C2=A0 =C2=A0 =C2=A0v9fs_post_do_syncfs(s, pdu, err);
> > + =C2=A0 =C2=A0 =C2=A0 =C2=A0return;
> > + =C2=A0 =C2=A0}
>=20
> This wasn't setting errno but passed the error in err.  It can stay
> like this if you change v9fs_post_do_syncfs().
>=20

nice catch. Will update.

-aneesh