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?
> + err = v9fs_pack(qiov_full.iov, qiov_full.niov, 0,
> ((char *)fidp->fs.xattr.value) + off,
> read_count);
> qemu_iovec_destroy(&qiov_full);
>
