On Mon, 23 Jan 2017 12:20:57 -0800 (PST) Stefano Stabellini <sstabell...@kernel.org> wrote:
> On Sat, 21 Jan 2017, Greg Kurz wrote: > > The current code tries to copy `read_count' bytes starting at offset > > `offset' from a `read_count`-sized iovec. This causes v9fs_pack() to > > fail with ENOBUFS. > > > > Since the PDU iovec is already partially filled with `offset' bytes, > > let's skip them when creating `qiov_full' and have v9fs_pack() to > > copy the whole of it. Moreover, this is consistent with the other > > places where v9fs_init_qiov_from_pdu() is called. > > > > This fixes commit "bcb8998fac16 9pfs: call v9fs_init_qiov_from_pdu > > before v9fs_pack". > > Sorry about that! > > > > Signed-off-by: Greg Kurz <gr...@kaod.org> > > --- > > hw/9pfs/9p.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c > > index fa58877570f6..f0eef1a3ef53 100644 > > --- a/hw/9pfs/9p.c > > +++ b/hw/9pfs/9p.c > > @@ -1685,8 +1685,8 @@ static int v9fs_xattr_read(V9fsState *s, V9fsPDU > > *pdu, V9fsFidState *fidp, > > } > > offset += err; > > > > - v9fs_init_qiov_from_pdu(&qiov_full, pdu, 0, read_count, false); > > - err = v9fs_pack(qiov_full.iov, qiov_full.niov, offset, > > + v9fs_init_qiov_from_pdu(&qiov_full, pdu, offset, read_count, false); > > v9fs_init_qiov_from_pdu calls init_in_iov_from_pdu passing read_count as > size argument. offset is not passed to init_in_iov_from_pdu, it is only > used to initialized qiov_full. > > In other words, don't we need to: > > v9fs_init_qiov_from_pdu(&qiov_full, pdu, offset, read_count + offset, > false); > > To make sure that qiov_full has "read_count + offset" bytes in it, and > qiov_full is initialized skipping the first "offset" bytes? > If we do that then qemu_iovec_concat() will skip offset bytes and then copy read_count + offset bytes or am I missing something ? > > > + err = v9fs_pack(qiov_full.iov, qiov_full.niov, 0, > > ((char *)fidp->fs.xattr.value) + off, > > read_count); > > qemu_iovec_destroy(&qiov_full); > >
