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Subject[RFC] Migrating net/sched to new module interface
Hi,

I'm working on net/sched to convert it to new module interface. I'm
going to add a new field 'owner' to struct Qdisc_ops. The init function
of each module registers the callback functions and a reference to
the module itself. When a qdisc is created (qdisc_create) I check
try_module_get() to see if I can use the registered callback functions
and if I can't I return -ENOSYS. When a qdisc is delete (qdisc_destroy)
I use module_put() to decrement the refcount. The attacched patch shows
this preliminar work on sch_api.c sch_generic.c.

The next step is to update the other schedulers removing
MOD_{INC,DEC}_USE_COUNT and adding the new 'owner' field.

This work is based on my (maybe poor) understanding on the new module
system, so I'm waiting some feedback before going on.

diff --exclude=diff.exclude -ru linux-2.5.orig/include/net/pkt_sched.h linux-2.5/include/net/pkt_sched.h
--- linux-2.5.orig/include/net/pkt_sched.h Sun Aug 11 22:07:18 2002
+++ linux-2.5/include/net/pkt_sched.h Thu Jan 2 22:50:57 2003
@@ -10,6 +10,7 @@
#include <linux/config.h>
#include <linux/types.h>
#include <linux/pkt_sched.h>
+#include <linux/module.h>
#include <net/pkt_cls.h>

#ifdef CONFIG_X86_TSC
@@ -67,6 +68,8 @@
int (*change)(struct Qdisc *, struct rtattr *arg);

int (*dump)(struct Qdisc *, struct sk_buff *);
+ /* Protects callbacks */
+ struct module *owner;
};

extern rwlock_t qdisc_tree_lock;
diff --exclude=diff.exclude -ru linux-2.5.orig/net/sched/sch_api.c linux-2.5/net/sched/sch_api.c
--- linux-2.5.orig/net/sched/sch_api.c Thu Jan 2 21:55:40 2003
+++ linux-2.5/net/sched/sch_api.c Thu Jan 2 22:59:26 2003
@@ -409,6 +409,10 @@
if (ops == NULL)
goto err_out;

+ err = -ENOSYS;
+ if (try_module_get(ops->owner) == 0)
+ goto err_module;
+
size = sizeof(*sch) + ops->priv_size;

sch = kmalloc(size, GFP_KERNEL);
@@ -416,12 +420,6 @@
if (!sch)
goto err_out;

- /* Grrr... Resolve race condition with module unload */
-
- err = -EINVAL;
- if (ops != qdisc_lookup_ops(kind))
- goto err_out;
-
memset(sch, 0, size);

skb_queue_head_init(&sch->q);
@@ -460,6 +458,8 @@
}

err_out:
+ module_put(ops->owner);
+err_module:
*errp = err;
if (sch)
kfree(sch);
diff --exclude=diff.exclude -ru linux-2.5.orig/net/sched/sch_generic.c linux-2.5/net/sched/sch_generic.c
--- linux-2.5.orig/net/sched/sch_generic.c Thu Jan 2 22:41:24 2003
+++ linux-2.5/net/sched/sch_generic.c Thu Jan 2 23:07:55 2003
@@ -29,6 +29,7 @@
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <linux/init.h>
+#include <linux/module.h>
#include <net/sock.h>
#include <net/pkt_sched.h>

@@ -356,6 +357,8 @@

.init = pfifo_fast_init,
.reset = pfifo_fast_reset,
+
+ .owner = THIS_MODULE,
};

struct Qdisc * qdisc_create_dflt(struct net_device *dev, struct Qdisc_ops *ops)
@@ -422,6 +425,7 @@
ops->reset(qdisc);
if (ops->destroy)
ops->destroy(qdisc);
+ module_put(ops->owner);
if (!(qdisc->flags&TCQ_F_BUILTIN))
kfree(qdisc);
}

ciao,
Luca
--
Reply-To: kronos@kronoz.cjb.net
Home: http://kronoz.cjb.net
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