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    SubjectRe: [PATCH 6/6] xen/xenbus-backend: Only register device if communication ring is local
    On Sat, Dec 10, 2011 at 07:29:51PM +0100, Bastian Blank wrote:
    > Signed-off-by: Bastian Blank <waldi@debian.org>
    > ---
    > drivers/xen/xenbus/Makefile | 2 +-
    > drivers/xen/xenbus/xenbus_dev_backend.c | 13 ++-----------
    > drivers/xen/xenbus/xenbus_dev_backend.h | 2 ++
    > drivers/xen/xenbus/xenbus_probe.c | 18 ++++++++++++++++++
    > 4 files changed, 23 insertions(+), 12 deletions(-)
    > create mode 100644 drivers/xen/xenbus/xenbus_dev_backend.h
    >
    > diff --git a/drivers/xen/xenbus/Makefile b/drivers/xen/xenbus/Makefile
    > index 31e2e90..d751f45 100644
    > --- a/drivers/xen/xenbus/Makefile
    > +++ b/drivers/xen/xenbus/Makefile
    > @@ -7,8 +7,8 @@ xenbus-objs += xenbus_comms.o
    > xenbus-objs += xenbus_xs.o
    > xenbus-objs += xenbus_probe.o
    >
    > +xenbus-be-objs-$(CONFIG_XEN_BACKEND) += xenbus_dev_backend.o
    > xenbus-be-objs-$(CONFIG_XEN_BACKEND) += xenbus_probe_backend.o
    > xenbus-objs += $(xenbus-be-objs-y)
    >
    > -obj-$(CONFIG_XEN_BACKEND) += xenbus_dev_backend.o
    > obj-$(CONFIG_XEN_XENBUS_FRONTEND) += xenbus_probe_frontend.o
    > diff --git a/drivers/xen/xenbus/xenbus_dev_backend.c b/drivers/xen/xenbus/xenbus_dev_backend.c
    > index a2092bd..fb87f1b 100644
    > --- a/drivers/xen/xenbus/xenbus_dev_backend.c
    > +++ b/drivers/xen/xenbus/xenbus_dev_backend.c
    > @@ -3,7 +3,6 @@
    > #include <linux/mm.h>
    > #include <linux/fs.h>
    > #include <linux/miscdevice.h>
    > -#include <linux/module.h>
    > #include <linux/capability.h>
    >
    > #include <xen/page.h>
    > @@ -11,8 +10,6 @@
    >
    > #include "xenbus_comms.h"
    >
    > -MODULE_LICENSE("GPL");
    > -
    > static int xenbus_backend_open(struct inode *inode, struct file *filp)
    > {
    > if (!capable(CAP_SYS_ADMIN))
    > @@ -67,23 +64,17 @@ static struct miscdevice xenbus_backend_dev = {
    > .fops = &xenbus_backend_fops,
    > };
    >
    > -static int __init xenbus_backend_init(void)
    > +int __init xenbus_backend_init(void)
    > {
    > int err;
    >
    > - if (!xen_initial_domain())
    > - return -ENODEV;
    > -
    > err = misc_register(&xenbus_backend_dev);
    > if (err)
    > printk(KERN_ERR "Could not register xenbus backend device\n");
    > return err;
    > }
    >
    > -static void __exit xenbus_backend_exit(void)
    > +void __exit xenbus_backend_exit(void)
    > {
    > misc_deregister(&xenbus_backend_dev);
    > }
    > -
    > -module_init(xenbus_backend_init);
    > -module_exit(xenbus_backend_exit);

    Why are we removing the module functionality?
    Can't this [the purpose of this patch] be done while still maintaining the module functionality?

    > diff --git a/drivers/xen/xenbus/xenbus_dev_backend.h b/drivers/xen/xenbus/xenbus_dev_backend.h
    > new file mode 100644
    > index 0000000..d986853
    > --- /dev/null
    > +++ b/drivers/xen/xenbus/xenbus_dev_backend.h
    > @@ -0,0 +1,2 @@
    > +int xenbus_backend_init(void);
    > +void xenbus_backend_exit(void);
    > diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
    > index 1b178c6..4eff095 100644
    > --- a/drivers/xen/xenbus/xenbus_probe.c
    > +++ b/drivers/xen/xenbus/xenbus_probe.c
    > @@ -60,6 +60,7 @@
    > #include <xen/hvm.h>
    >
    > #include "xenbus_comms.h"
    > +#include "xenbus_dev_backend.h"
    > #include "xenbus_probe.h"
    >
    >
    > @@ -641,6 +642,10 @@ EXPORT_SYMBOL_GPL(xenbus_dev_cancel);
    > /* A flag to determine if xenstored is 'ready' (i.e. has started) */
    > int xenstored_ready;
    >
    > +/* A flag to determine if xenstored is 'local' */
    > +#ifdef CONFIG_XEN_BACKEND
    > +static int xenstored_local;

    bool?

    > +#endif
    >
    > int register_xenstore_notifier(struct notifier_block *nb)
    > {
    > @@ -675,6 +680,14 @@ static int __init xenbus_probe_initcall(void)
    > if (!xen_domain())
    > return -ENODEV;
    >
    > +#ifdef CONFIG_XEN_BACKEND
    > + if (xenstored_local) {
    > + int ret = xenbus_backend_init();
    > + if (ret)
    > + return ret;
    > + }
    > +#endif
    > +
    > if (xen_initial_domain() || xen_hvm_domain())
    > return 0;
    >
    > @@ -747,9 +760,14 @@ static int __init xenbus_init(void)
    > if (xen_store_evtchn)
    > xenstored_ready = 1;
    > else {
    > +#ifdef CONFIG_XEN_BACKEND
    > + xenstored_local = 1;
    > err = xenstored_local_init();
    > if (err)
    > goto out_error;
    > +#else
    > + BUG();

    No way. A WARN, sure - but BUG() is way too intense for this.

    > +#endif
    > }
    > xen_store_interface = mfn_to_virt(xen_store_mfn);
    > }
    > --
    > 1.7.7.3
    >
    > --
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