linux-kernel - Re: SLUB sysfs support

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Date:	Thu, 27 Dec 2007 15:22:28 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	Al Viro <viro@...IV.linux.org.uk>
cc:	Theodore Tso <tytso@....edu>, Andi Kleen <andi@...stfloor.org>,
	Willy Tarreau <w@....eu>, Steven Rostedt <rostedt@...dmis.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: SLUB sysfs support

On Thu, 27 Dec 2007, Al Viro wrote:

> On Thu, Dec 27, 2007 at 12:28:14PM -0800, Christoph Lameter wrote:
> > Hmmm.. If I separately allocate the kobject then I can no longer get to 
> > the kmem_cache structure from the kobject. 
> > 
> > I need to add a second kobject_del to sysfs_slab_remove() to make sysfs 
> > completely forget about the object?
> > 
> > Probably should track down any remaining symlinks at that point and nuke 
> > them too. Isnt there some way to convince sysfs to remove the symlinks 
> > if the target vanishes?
> 
> Don't bother with separate allocation.
> 
> a) remove symlink when slab goes away

Ok. Need to think about how to code that.

> b) instead of kfree() in slab removal do kobject_put() if you have sysfs stuff

Hmmmm.... Okay. Patch follows but its strange to do a kobject_put after a 
kobject_del().

> c) have ->release() of these kobjects do kfree()

In slab_ktype?

---
 mm/slub.c |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c	2007-12-27 15:09:38.000000000 -0800
+++ linux-2.6/mm/slub.c	2007-12-27 15:21:12.000000000 -0800
@@ -247,7 +247,10 @@ static void sysfs_slab_remove(struct kme
 static inline int sysfs_slab_add(struct kmem_cache *s) { return 0; }
 static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p)
 							{ return 0; }
-static inline void sysfs_slab_remove(struct kmem_cache *s) {}
+static inline void sysfs_slab_remove(struct kmem_cache *s)
+{
+	kfree(s);
+}
 #endif
 
 /********************************************************************
@@ -2322,7 +2325,6 @@ void kmem_cache_destroy(struct kmem_cach
 		if (kmem_cache_close(s))
 			WARN_ON(1);
 		sysfs_slab_remove(s);
-		kfree(s);
 	} else
 		up_write(&slub_lock);
 }
@@ -3940,6 +3942,13 @@ static ssize_t slab_attr_store(struct ko
 	return err;
 }
 
+static void slab_release(struct kobject *kobj)
+{
+	struct kmem_cache *s = to_slab(kobj);
+
+	kfree(s);
+}
+
 static struct sysfs_ops slab_sysfs_ops = {
 	.show = slab_attr_show,
 	.store = slab_attr_store,
@@ -3947,6 +3956,7 @@ static struct sysfs_ops slab_sysfs_ops =
 
 static struct kobj_type slab_ktype = {
 	.sysfs_ops = &slab_sysfs_ops,
+	.release = slab_release
 };
 
 static int uevent_filter(struct kset *kset, struct kobject *kobj)
@@ -4048,6 +4058,7 @@ static void sysfs_slab_remove(struct kme
 {
 	kobject_uevent(&s->kobj, KOBJ_REMOVE);
 	kobject_del(&s->kobj);
+	kobject_put(&s->kobj);
 }
 
 /*

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