On Thu, Oct 13, 2016 at 01:42:06PM +0200, Hannes Reinecke wrote:
> On 10/12/2016 03:06 PM, Johannes Thumshirn wrote:
> > Implement kref backed reference counting instead of rolling our own. This
> > elimnates the need of the following fields in 'struct fc_bsg_job':
> > * ref_cnt
> > * state_flags
> > * job_lock
> > bringing us close to unification of 'struct fc_bsg_job' and 'struct bsg_job'.
> >
> > Signed-off-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
> > ---
> > drivers/scsi/scsi_transport_fc.c | 38 +++++++++-----------------------------
> > include/scsi/scsi_transport_fc.h | 4 +---
> > 2 files changed, 10 insertions(+), 32 deletions(-)
> >
> > diff --git a/drivers/scsi/scsi_transport_fc.c b/drivers/scsi/scsi_transport_fc.c
> > index 96b3a2e..b0e28af 100644
> > --- a/drivers/scsi/scsi_transport_fc.c
> > +++ b/drivers/scsi/scsi_transport_fc.c
> > @@ -3560,16 +3560,9 @@ fc_vport_sched_delete(struct work_struct *work)
> > * @job: fc_bsg_job that is to be torn down
> > */
> > static void
> > -fc_destroy_bsgjob(struct fc_bsg_job *job)
> > +fc_destroy_bsgjob(struct kref *kref)
> > {
> > - unsigned long flags;
> > -
> > - spin_lock_irqsave(&job->job_lock, flags);
> > - if (job->ref_cnt) {
> > - spin_unlock_irqrestore(&job->job_lock, flags);
> > - return;
> > - }
> > - spin_unlock_irqrestore(&job->job_lock, flags);
> > + struct fc_bsg_job *job = container_of(kref, struct fc_bsg_job, kref);
> >
> > put_device(job->dev); /* release reference for the request */
> >
> > @@ -3620,15 +3613,9 @@ EXPORT_SYMBOL_GPL(fc_bsg_jobdone);
> > static void fc_bsg_softirq_done(struct request *rq)
> > {
> > struct fc_bsg_job *job = rq->special;
> > - unsigned long flags;
> > -
> > - spin_lock_irqsave(&job->job_lock, flags);
> > - job->state_flags |= FC_RQST_STATE_DONE;
> > - job->ref_cnt--;
> > - spin_unlock_irqrestore(&job->job_lock, flags);
> >
> > blk_end_request_all(rq, rq->errors);
> > - fc_destroy_bsgjob(job);
> > + kref_put(&job->kref, fc_destroy_bsgjob);
> > }
> >
> > /**
> Hmm. blk_end_request_all() (potentially) triggers a recursion into all
> .end_io callbacks, which might end up doing god-knows-what.
> With some delays in doing so
> During that time we have no idea that bsg_softirq_done() is actually
> running, and we might clash with eg. timeouts or somesuch.
>
> Maybe it's an idea to move blk_end_request_all into the kref destroy
> callback; that way we're guaranteed to call it only once and would avoid
> this situation.
This _could_ explain the panic with zfcp. Fixed that for v3.
--
Johannes Thumshirn Storage
jthumshirn@xxxxxxx +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850
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