Messages in this thread | | | Subject | Re: [PATCH v2 1/5] vfio: ccw: fix cleanup if cp_prefetch fails | From | Halil Pasic <> | Date | Mon, 23 Apr 2018 13:38:54 +0200 |
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On 04/23/2018 01:01 PM, Dong Jia Shi wrote: > From: Halil Pasic <pasic@linux.vnet.ibm.com> > > If the translation of a channel program fails, we may end up attempting > to clean up (free, unpin) stuff that never got translated (and allocated, > pinned) in the first place. > > By adjusting the lengths of the chains accordingly (so the element that > failed, and all subsequent elements are excluded) cleanup activities > based on false assumptions can be avoided. > > Let's make sure cp_free works properly after cp_prefetch returns with an > error by setting ch_len of a ccw chain to the number of the translated > CCWs on that chain. > > Acked-by: Pierre Morel <pmorel@linux.vnet.ibm.com> > Reviewed-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> > Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com> > Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
AFAIR we came to the conclusion that this one is stable material. [https://www.spinics.net/lists/kvm/msg166629.html]
> --- > drivers/s390/cio/vfio_ccw_cp.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c > index 2c7550797ec2..62d66e195304 100644 > --- a/drivers/s390/cio/vfio_ccw_cp.c > +++ b/drivers/s390/cio/vfio_ccw_cp.c > @@ -715,6 +715,10 @@ void cp_free(struct channel_program *cp) > * and stores the result to ccwchain list. @cp must have been > * initialized by a previous call with cp_init(). Otherwise, undefined > * behavior occurs. > + * For each chain composing the channel program: > + * - On entry ch_len holds the count of CCW to be translated. > + * - On exit ch_len is adjusted to the count of successfully translated CCW. > + * This allows cp_free to find in ch_len the count of CCW to free in a chain. > * > * The S/390 CCW Translation APIS (prefixed by 'cp_') are introduced > * as helpers to do ccw chain translation inside the kernel. Basically > @@ -749,11 +753,18 @@ int cp_prefetch(struct channel_program *cp) > for (idx = 0; idx < len; idx++) { > ret = ccwchain_fetch_one(chain, idx, cp); > if (ret) > - return ret; > + goto out_err; > } > } > > return 0; > +out_err: > + /* Only cleanup the chain elements that were actually translated. */ > + chain->ch_len = idx; > + list_for_each_entry_continue(chain, &cp->ccwchain_list, next) { > + chain->ch_len = 0; > + } > + return ret; > } > > /** >
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