On Mon, Aug 12, 2019 at 05:04:55PM -0400, Masayoshi Mizuma wrote: > @@ -251,6 +259,11 @@ static void virtio_fs_hiprio_dispatch_work(struct > work_struct *work) > notify = virtqueue_kick_prepare(vq); > spin_unlock(&fsvq->lock); > > + trace_virtio_fs_hiprio_request_dispatched( > + forget->ih.opcode, forget->ih.unique, > + forget->ih.nodeid, forget->ih.len, > + notify); > +
It is safer to trace the request before placing it in the queue and before releasing fsvq->lock. I'm concerned that a fast device may complete the request and invoke virtio_fs_hiprio_done_work() so that kfree(req) is called before we've finished tracing it. (We cannot rely on virtqueue_notify() because devices may poll the virtqueue, so as soon as the request has been added to the virtqueue it may be completed.) > @@ -914,6 +931,10 @@ static int virtio_fs_enqueue_req(struct virtqueue *vq, > struct fuse_req *req) > > spin_unlock(&fsvq->lock); > > + trace_virtio_fs_request_dispatched( > + req->in.h.opcode, req->in.h.unique, > + req->in.h.nodeid, req->in.h.len, req->flags, notify); > + > if (notify) > virtqueue_notify(vq); Same here, we no longer control the lifetime of req so it's not safe to access it after virtqueue_add_sgs() + spin_unlock(&fsvq->lock).
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