Re: [RFC v1 2/4] vfio-ccw: No need to call cp_free on an error in cp_init

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On 07/02/2019 12:15 PM, Eric Farman wrote:


On 7/2/19 9:58 AM, Farhan Ali wrote:


On 07/02/2019 04:42 AM, Cornelia Huck wrote:
On Mon,  1 Jul 2019 12:23:44 -0400
Farhan Ali <alifm@xxxxxxxxxxxxx> wrote:

We don't set cp->initialized to true so calling cp_free
will just return and not do anything.

Signed-off-by: Farhan Ali <alifm@xxxxxxxxxxxxx>
---
   drivers/s390/cio/vfio_ccw_cp.c | 2 --
   1 file changed, 2 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_cp.c
b/drivers/s390/cio/vfio_ccw_cp.c
index 5ac4c1e..cab1be9 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -647,8 +647,6 @@ int cp_init(struct channel_program *cp, struct
device *mdev, union orb *orb)
         /* Build a ccwchain for the first CCW segment */
       ret = ccwchain_handle_ccw(orb->cmd.cpa, cp);
-    if (ret)
-        cp_free(cp);

Makes sense; hopefully ccwchain_handle_ccw() cleans up correctly on
error :) (I think it does)


I have checked that it does as well, but wouldn't hurt if someone else
also glances over once again :)

Oh noes.  What happens once we start encountering TICs?  If we do:

ccwchain_handle_ccw()	(OK)
ccwchain_loop_tic()	(OK)
ccwchain_handle_ccw()	(FAIL)

The first _handle_ccw() will have added a ccwchain to the cp list, which
doesn't appear to get cleaned up now.  That used to be done in cp_init()
until I squashed cp_free and cp_unpin_free.  :(

Yup, you are right we are not freeing the chain correctly. Will fix it in v2.


Maybe add a comment

/* ccwchain_handle_ccw() already cleans up on error */

so we don't stumble over this in the future?

Sure.


(Also, does this want a Fixes: tag?)

This might warrant a fixes tag as well.

         if (!ret)
           cp->initialized = true;






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