On Donnerstag, 19. Dezember 2019 01:42:51 CET Stefano Stabellini wrote:
> From: Stefano Stabellini <stefano.stabell...@xilinx.com>
>
> init_in_iov_from_pdu might not be able to allocate the full buffer size
> requested, which comes from the client and could be larger than the
> transport has available at the time of the request. Specifically, this
> can happen with read operations, with the client requesting a read up to
> the max allowed, which might be more than the transport has available at
> the time.
I haven't looked thoroughly at this yet, but that's about addressing a
temporary, not a permanent transport buffer size limitation, right? Because if
it was a permanent one, then probably an adjusted (lowered) msize should be
returned on R_version response to client as well.
I wonder why I never triggered this issue, because I was experimenting with
huge msize values for 9pfs performance checks. Was there anything specific to
trigger this issue?
> Today the implementation of init_in_iov_from_pdu throws an error, both
> Xen and Virtio.
>
> Instead, change the V9fsTransport interface so that the size becomes a
> pointer and can be limited by the implementation of
> init_in_iov_from_pdu.
>
> Change both the Xen and Virtio implementations to set the size to the
> size of the buffer they managed to allocate, instead of throwing an
> error.
>
> Signed-off-by: Stefano Stabellini <stefano.stabell...@xilinx.com>
> CC: gr...@kaod.org
> CC: anthony.per...@citrix.com
> ---
> hw/9pfs/9p.c | 22 +++++++++++++++-------
> hw/9pfs/9p.h | 2 +-
> hw/9pfs/virtio-9p-device.c | 10 +++-------
> hw/9pfs/xen-9p-backend.c | 12 ++++--------
> 4 files changed, 23 insertions(+), 23 deletions(-)
>
> diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> index bdf7919abf..d6c89ce608 100644
> --- a/hw/9pfs/9p.c
> +++ b/hw/9pfs/9p.c
> @@ -1682,22 +1682,30 @@ out_nofid:
> * with qemu_iovec_destroy().
> */
> static void v9fs_init_qiov_from_pdu(QEMUIOVector *qiov, V9fsPDU *pdu,
> - size_t skip, size_t size,
> + size_t skip, size_t *size,
> bool is_write)
> {
> QEMUIOVector elem;
> struct iovec *iov;
> unsigned int niov;
> + size_t alloc_size = *size + skip;
>
> if (is_write) {
> - pdu->s->transport->init_out_iov_from_pdu(pdu, &iov, &niov, size +
> skip); + pdu->s->transport->init_out_iov_from_pdu(pdu, &iov, &niov,
> alloc_size); } else {
> - pdu->s->transport->init_in_iov_from_pdu(pdu, &iov, &niov, size +
> skip); + pdu->s->transport->init_in_iov_from_pdu(pdu, &iov, &niov,
> &alloc_size); + }
> +
> + if (alloc_size < skip)
> + {
> + *size = 0;
> + } else {
> + *size = alloc_size - skip;
> }
>
Code style nitpicking:
ERROR: that open brace { should be on the previous line
#56: FILE: hw/9pfs/9p.c:1699:
+ if (alloc_size < skip)
+ {
>
> static int v9fs_xattr_read(V9fsState *s, V9fsPDU *pdu, V9fsFidState *fidp,
> @@ -1722,7 +1730,7 @@ static int v9fs_xattr_read(V9fsState *s, V9fsPDU *pdu,
> V9fsFidState *fidp, }
> offset += err;
>
> - v9fs_init_qiov_from_pdu(&qiov_full, pdu, offset, read_count, false);
> + v9fs_init_qiov_from_pdu(&qiov_full, pdu, offset, &read_count, false);
> err = v9fs_pack(qiov_full.iov, qiov_full.niov, 0,
> ((char *)fidp->fs.xattr.value) + off,
> read_count);
> @@ -1852,7 +1860,7 @@ static void coroutine_fn v9fs_read(void *opaque)
> QEMUIOVector qiov;
> int32_t len;
>
> - v9fs_init_qiov_from_pdu(&qiov_full, pdu, offset + 4, max_count,
> false); + v9fs_init_qiov_from_pdu(&qiov_full, pdu, offset + 4,
> &max_count, false); qemu_iovec_init(&qiov, qiov_full.niov);
> do {
> qemu_iovec_reset(&qiov);
> @@ -2085,7 +2093,7 @@ static void coroutine_fn v9fs_write(void *opaque)
> return;
> }
> offset += err;
> - v9fs_init_qiov_from_pdu(&qiov_full, pdu, offset, count, true);
> + v9fs_init_qiov_from_pdu(&qiov_full, pdu, offset, &count, true);
> trace_v9fs_write(pdu->tag, pdu->id, fid, off, count, qiov_full.niov);
>
> fidp = get_fid(pdu, fid);
> diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h
> index 8883761b2c..50f7e21da6 100644
> --- a/hw/9pfs/9p.h
> +++ b/hw/9pfs/9p.h
> @@ -365,7 +365,7 @@ struct V9fsTransport {
> ssize_t (*pdu_vunmarshal)(V9fsPDU *pdu, size_t offset, const char
> *fmt, va_list ap);
> void (*init_in_iov_from_pdu)(V9fsPDU *pdu, struct iovec **piov,
> - unsigned int *pniov, size_t size);
> + unsigned int *pniov, size_t *size);
> void (*init_out_iov_from_pdu)(V9fsPDU *pdu, struct iovec **piov,
> unsigned int *pniov, size_t size); void (*push_and_notify)(V9fsPDU
> *pdu);
> diff --git a/hw/9pfs/virtio-9p-device.c b/hw/9pfs/virtio-9p-device.c
> index 775e8ff766..68873c3f5f 100644
> --- a/hw/9pfs/virtio-9p-device.c
> +++ b/hw/9pfs/virtio-9p-device.c
> @@ -145,19 +145,15 @@ static ssize_t virtio_pdu_vunmarshal(V9fsPDU *pdu,
> size_t offset, }
>
> static void virtio_init_in_iov_from_pdu(V9fsPDU *pdu, struct iovec **piov,
> - unsigned int *pniov, size_t size)
> + unsigned int *pniov, size_t *size)
> {
> V9fsState *s = pdu->s;
> V9fsVirtioState *v = container_of(s, V9fsVirtioState, state);
> VirtQueueElement *elem = v->elems[pdu->idx];
> size_t buf_size = iov_size(elem->in_sg, elem->in_num);
>
> - if (buf_size < size) {
> - VirtIODevice *vdev = VIRTIO_DEVICE(v);
> -
> - virtio_error(vdev,
> - "VirtFS reply type %d needs %zu bytes, buffer has
> %zu", - pdu->id + 1, size, buf_size);
> + if (buf_size < *size) {
> + *size = buf_size;
> }
>
> *piov = elem->in_sg;
> diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
> index 3f54a21c76..3994a356d4 100644
> --- a/hw/9pfs/xen-9p-backend.c
> +++ b/hw/9pfs/xen-9p-backend.c
> @@ -187,7 +187,7 @@ static void xen_9pfs_init_out_iov_from_pdu(V9fsPDU *pdu,
> static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU *pdu,
> struct iovec **piov,
> unsigned int *pniov,
> - size_t size)
> + size_t *size)
> {
> Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
> Xen9pfsRing *ring = &xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings];
> @@ -197,15 +197,11 @@ static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU
> *pdu, g_free(ring->sg);
>
> ring->sg = g_malloc0(sizeof(*ring->sg) * 2);
> - xen_9pfs_in_sg(ring, ring->sg, &num, pdu->idx, size);
> + xen_9pfs_in_sg(ring, ring->sg, &num, pdu->idx, *size);
>
> buf_size = iov_size(ring->sg, num);
> - if (buf_size < size) {
> - xen_pv_printf(&xen_9pfs->xendev, 0, "Xen 9pfs request type %d"
> - "needs %zu bytes, buffer has %zu\n", pdu->id, size,
> - buf_size);
> - xen_be_set_state(&xen_9pfs->xendev, XenbusStateClosing);
> - xen_9pfs_disconnect(&xen_9pfs->xendev);
> + if (buf_size < *size) {
> + *size = buf_size;
> }
>
> *piov = ring->sg;
Best regards,
Christian Schoenebeck
