On Thu, 2017-04-13 at 13:14 +0530, Varun Prakash wrote:
> Hi Nicholas,
>
> On Tue, Apr 04, 2017 at 10:36:50AM +0530, Varun Prakash wrote:
> > Hi Nicholas and Bart,
> >
> > On Sun, Apr 02, 2017 at 03:59:05PM -0700, Nicholas A. Bellinger wrote:
> > > On Thu, 2017-03-30 at 10:12 -0700, Bart Van Assche wrote:
> > > > While releasing a command __iscsit_free_cmd() can be called multiple
> > > > times but .iscsit_release_cmd() must be called only once. Hence move
> > > > the .iscsit_release_cmd() call into iscsit_release_cmd(). The latter
> > > > function is only called once per command. The only driver that defines
> > > > the .iscsit_release_cmd() callback is the cxgbit driver so this change
> > > > only affects the cxgbit driver.
> > > >
> > > > Fixes: 7ec811a8e9c3 ("iscsi-target: add void (*iscsit_release_cmd)()")
> > > > Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
> > > > Cc: Varun Prakash <varun@xxxxxxxxxxx>
> > > > Cc: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
> > > > Cc: <stable@xxxxxxxxxxxxxxx>
> > > > ---
> > > > drivers/target/iscsi/iscsi_target_util.c | 15 +++++++++------
> > > > 1 file changed, 9 insertions(+), 6 deletions(-)
> > > >
> > >
> > > Applied to target-pending/for-next, but dropping the stable CC' because
> > > the single caller in cxgbit_release_cmd() is already checking to ensure
> > > resources are only released on the first invocation.
> > >
> > > So it's not a bug-fix.
> >
> > In case of DDP cxgbit driver assigns cmd->se_cmd.t_data_sg to ttinfo->sgl
> > and calls dma_map_sg(), cxgbit_release_cmd() calls dma_unmap_sg(), it needs
> > a valid sg(ttinfo->sgl), before calling iscsit_release_cmd()
> > cmd->se_cmd.t_data_sg gets freed so ttinfo->sgl will not be valid if we move
> > ->iscsit_release_cmd() to iscsit_release_cmd().
>
> Please drop this patch, it will regress cxgbit driver, with this patch
> scatterlist is freed before calling ->iscsit_release_cmd(), cxgbit
> calls dma_unmap_sg() so scatterlist should not be freed before calling
> ->iscst_release_cmd().
>
Thanks for the heads up. Dropping this patch for now.
To address this, AFAICT the cleanest approach is to simply do the
unmapping of DDP SGLs currently done by cxgbit_release_cmd(), directly
from a cxgbit specific iscsit_transport->iscsit_queue_rsp() callback.
That way, we can unmap the DDP SGLs immediately before invoking
iscsit_queue_rsp() from a cxgbit specific handler, and drop the
iscsi_transport->iscsit_release_cmd() callback alltogether.
WDYT..?