On 08/05/2016 12:43 AM, Hannes Reinecke wrote:
On 08/04/2016 04:59 PM, Bart Van Assche wrote:
On 08/03/16 06:13, Hannes Reinecke wrote:
As usual, comments and reviews are welcome.
Great work :-) Have you been testing these patches against the LIO FCoE
target driver? In that case you might need to port the following patch
to LIO, a patch that fixes a subtle data corruption issue:
https://sourceforge.net/p/scst/svn/4969.
Indeed I have. With this patchset I've managed to run FCoE over virtio
with LIO running on the host. Quite cool, methinks :-)
And indeed, your patch seem to be helping with the issues I've seen
(mysterious out-of-order frames and wireshark complaining about invalid
frames).
Still a bit hackish, though. Can't we move the data destructor into the
skb itself and not free the data in the target core?
Hello Hannes,
Several LIO drivers already support sending data asynchronously to the
initiator, e.g. the ib_srpt and qla2x00t drivers. These drivers avoid
that struct se_cmd and its data buffer are freed before sending finished
by passing the TARGET_SCF_ACK_KREF flag to target_submit_cmd_map_sgls()
and by calling target_put_sess_cmd() after the data transfer has
finished. Since the tcm_fc driver already specifies TARGET_SCF_ACK_KREF
when submitting commands to the LIO core I think what's needed to make
use_sg=1 safe in the tcm_fc driver is for use_sg=1 to move the
target_put_sess_cmd() call from ft_queue_status() into a callback
function that is called when transmitting data has finished. Maybe the
SKBTX_DEV_ZEROCOPY flag can be used to make the network stack invoke an
appropriate callback function. See e.g. xenvif_zerocopy_callback() in
the xen-netback driver.
Bart.
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