[patch] kref shrinkage patches -- 1 of 2 -- kref shrinkage

Ravikiran G Thirumalai
2004-07-20T12:24:15Z

Greg,
Here's the first step towards getting to kref_get_rcu :)
This patch is to shrink the kref object by removing the
function pointer 'release' from the kref object, and modifying
kref_init and kref_put interfaces so that kref_init will not take
the release pointer anymore and kref_put will. Patch will probably talk
better.

Just had a question about definition of kref_get though,
why does it need to return struct kref * ? struct kref * is anywayz
being passed to it, hence the caller has it anywayz -- so it doesn't
value add anything afaics (but i might have limited vision so pls correct me)
In fact, I see that the scsi applications of kref have code like

<quote drivers/scsi/sd.c>

if (!kref_get(&sdkp->kref))
goto out_sdkp;

</>

the goto can never happen afaics. IMO, kref_get must return void to
avoid such wrong usage -- or atleast add some bold comments . Do let me
know and I can make a patch to do either.

Thanks,
Kiran

Signed-off-by: Ravikiran Thirumalai <kiran@in.ibm.com>

diff -ruN -X dontdiff2 linux-2.6.7/include/linux/kref.h kref-2.6.7/include/linux/kref.h
--- linux-2.6.7/include/linux/kref.h 2004-06-16 10:48:59.000000000 +0530
+++ kref-2.6.7/include/linux/kref.h 2004-07-20 12:53:24.226739304 +0530
@@ -8,6 +8,9 @@
* Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org>
* Copyright (C) 2002-2003 Open Source Development Labs
*
+ * 07/2004 - struct kref shrinkage by Ravikiran Thirumalai <kiran@in.ibm.com>
+ * Copyright (C) 2004 IBM Corp.
+ *
* This file is released under the GPLv2.
*
*/
@@ -21,12 +24,11 @@

struct kref {
atomic_t refcount;
- void (*release)(struct kref *kref);
};

-void kref_init(struct kref *kref, void (*release)(struct kref *));
+void kref_init(struct kref *kref);
struct kref *kref_get(struct kref *kref);
-void kref_put(struct kref *kref);
+void kref_put(struct kref *kref, void (*release) (struct kref *kref));

#endif /* _KREF_H_ */
diff -ruN -X dontdiff2 linux-2.6.7/lib/kref.c kref-2.6.7/lib/kref.c
--- linux-2.6.7/lib/kref.c 2004-06-16 10:50:26.000000000 +0530
+++ kref-2.6.7/lib/kref.c 2004-07-20 13:00:36.819975136 +0530
@@ -7,6 +7,9 @@
* based on lib/kobject.c which was:
* Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org>
*
+ * 07/2004 - kref object shrinkage by Ravikiran Thirumalai <kiran@in.ibm.com>
+ * Copyright (C) 2004 IBM Corp.
+ *
* This file is released under the GPLv2.
*
*/
@@ -19,15 +22,10 @@
/**
* kref_init - initialize object.
* @kref: object in question.
- * @release: pointer to a function that will clean up the object
- * when the last reference to the object is released.
- * This pointer is required.
*/
-void kref_init(struct kref *kref, void (*release)(struct kref *kref))
+void kref_init(struct kref *kref)
{
- WARN_ON(release == NULL);
atomic_set(&kref->refcount,1);
- kref->release = release;
}

/**
@@ -44,14 +42,17 @@
/**
* kref_put - decrement refcount for object.
* @kref: object.
- *
- * Decrement the refcount, and if 0, call kref->release().
+ * @release: pointer to the function that will clean up the object
+ * when the last reference to the object is released.
+ * This pointer is required.
+ * Decrement the refcount, and if 0, call release().
*/
-void kref_put(struct kref *kref)
+void kref_put(struct kref *kref, void (*release) (struct kref *kref))
{
+ WARN_ON(release == NULL);
if (atomic_dec_and_test(&kref->refcount)) {
pr_debug("kref cleaning up\n");
- kref->release(kref);
+ release(kref);
}
}