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Date: Fri, 18 Jan 2013 08:59:19 +0800
From: Liu Bo <bo.li.liu@...cle.com>
To: Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
linux-btrfs@...r.kernel.org, zab@...bo.net, cl@...ux.com,
penberg@...nel.org
Subject: Re: [PATCH V2] mm/slab: add a leak decoder callback
On Thu, Jan 17, 2013 at 05:34:46PM +0900, Joonsoo Kim wrote:
> Hello, Liu Bo.
>
> On Wed, Jan 16, 2013 at 11:03:13AM +0800, Liu Bo wrote:
> > This adds a leak decoder callback so that slab destruction
> > can use to generate debugging output for the allocated objects.
> >
> > Callers like btrfs are using their own leak tracking which will
> > manage allocated objects in a list(or something else), this does
> > indeed the same thing as what slab does. So adding a callback
> > for leak tracking can avoid this as well as runtime overhead.
> >
> > (The idea is from Zach Brown <zab@...bo.net>.)
> >
> > Signed-off-by: Liu Bo <bo.li.liu@...cle.com>
> > ---
> > v2: add a wrapper API for slab destruction to make decoder only
> > work in particular path.
> >
> > fs/btrfs/extent_io.c | 26 ++++++++++++++++++++++++--
> > fs/btrfs/extent_map.c | 13 ++++++++++++-
> > include/linux/slab.h | 2 ++
> > include/linux/slab_def.h | 1 +
> > include/linux/slub_def.h | 1 +
> > mm/slab_common.c | 17 ++++++++++++++++-
> > mm/slub.c | 2 ++
> > 7 files changed, 58 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> > index bcc8dff..355c7fc 100644
> > --- a/fs/btrfs/extent_io.c
> > +++ b/fs/btrfs/extent_io.c
> > @@ -63,6 +63,26 @@ tree_fs_info(struct extent_io_tree *tree)
> > return btrfs_sb(tree->mapping->host->i_sb);
> > }
> >
> > +static void extent_state_leak_decoder(void *object)
> > +{
> > + struct extent_state *state = object;
> > +
> > + printk(KERN_ERR "btrfs state leak: start %llu end %llu "
> > + "state %lu in tree %p refs %d\n",
> > + (unsigned long long)state->start,
> > + (unsigned long long)state->end,
> > + state->state, state->tree, atomic_read(&state->refs));
> > +}
> > +
> > +static void extent_buffer_leak_decoder(void *object)
> > +{
> > + struct extent_buffer *eb = object;
> > +
> > + printk(KERN_ERR "btrfs buffer leak start %llu len %lu "
> > + "refs %d\n", (unsigned long long)eb->start,
> > + eb->len, atomic_read(&eb->refs));
> > +}
> > +
> > int __init extent_io_init(void)
> > {
> > extent_state_cache = kmem_cache_create("btrfs_extent_state",
> > @@ -115,9 +135,11 @@ void extent_io_exit(void)
> > */
> > rcu_barrier();
> > if (extent_state_cache)
> > - kmem_cache_destroy(extent_state_cache);
> > + kmem_cache_destroy_decoder(extent_state_cache,
> > + extent_state_leak_decoder);
> > if (extent_buffer_cache)
> > - kmem_cache_destroy(extent_buffer_cache);
> > + kmem_cache_destroy_decoder(extent_buffer_cache,
> > + extent_buffer_leak_decoder);
> > }
> >
> > void extent_io_tree_init(struct extent_io_tree *tree,
> > diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
> > index f359e4c..bccba3d 100644
> > --- a/fs/btrfs/extent_map.c
> > +++ b/fs/btrfs/extent_map.c
> > @@ -16,6 +16,16 @@ static LIST_HEAD(emaps);
> > static DEFINE_SPINLOCK(map_leak_lock);
> > #endif
> >
> > +static void extent_map_leak_decoder(void *object)
> > +{
> > + struct extent_map *em = object;
> > +
> > + printk(KERN_ERR "btrfs ext map leak: start %llu len %llu block %llu "
> > + "flags %lu refs %d in tree %d compress %d\n",
> > + em->start, em->len, em->block_start, em->flags,
> > + atomic_read(&em->refs), em->in_tree, (int)em->compress_type);
> > +}
> > +
> > int __init extent_map_init(void)
> > {
> > extent_map_cache = kmem_cache_create("btrfs_extent_map",
> > @@ -39,7 +49,8 @@ void extent_map_exit(void)
> > }
> >
> > if (extent_map_cache)
> > - kmem_cache_destroy(extent_map_cache);
> > + kmem_cache_destroy_decoder(extent_map_cache,
> > + extent_map_leak_decoder);
> > }
> >
> > /**
> > diff --git a/include/linux/slab.h b/include/linux/slab.h
> > index 5d168d7..5c6a8d8 100644
> > --- a/include/linux/slab.h
> > +++ b/include/linux/slab.h
> > @@ -114,6 +114,7 @@ struct kmem_cache {
> > const char *name; /* Slab name for sysfs */
> > int refcount; /* Use counter */
> > void (*ctor)(void *); /* Called on object slot creation */
> > + void (*decoder)(void *);/* Called on object slot leak detection */
> > struct list_head list; /* List of all slab caches on the system */
> > };
> > #endif
> > @@ -132,6 +133,7 @@ struct kmem_cache *
> > kmem_cache_create_memcg(struct mem_cgroup *, const char *, size_t, size_t,
> > unsigned long, void (*)(void *), struct kmem_cache *);
> > void kmem_cache_destroy(struct kmem_cache *);
> > +void kmem_cache_destroy_decoder(struct kmem_cache *, void (*)(void *));
> > int kmem_cache_shrink(struct kmem_cache *);
> > void kmem_cache_free(struct kmem_cache *, void *);
> >
>
> For SLUB,
> kmem_cache_destroy_decoder works when CONFIG_SLUB_DEBUG is enable.
> But, user for kmem_cache_destroy_decoder can't know about it.
>
> How about below approach?
>
> #ifdef CONFIG_SLUB_DEBUG
> void kmem_cache_destroy_decoder(struct kmem_cache *, void (*)(void *));
> #else
> #define kmem_cache_destroy_decoder(s) kmem_cache_destory(s)
> #endif
Good Point! Will update the patch as suggested :)
thanks,
liubo
>
> > diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h
> > index 8bb6e0e..7ca8309 100644
> > --- a/include/linux/slab_def.h
> > +++ b/include/linux/slab_def.h
> > @@ -48,6 +48,7 @@ struct kmem_cache {
> >
> > /* constructor func */
> > void (*ctor)(void *obj);
> > + void (*decoder)(void *obj);
> >
> > /* 4) cache creation/removal */
> > const char *name;
> > diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
> > index 9db4825..fc18af7 100644
> > --- a/include/linux/slub_def.h
> > +++ b/include/linux/slub_def.h
> > @@ -93,6 +93,7 @@ struct kmem_cache {
> > gfp_t allocflags; /* gfp flags to use on each alloc */
> > int refcount; /* Refcount for slab cache destroy */
> > void (*ctor)(void *);
> > + void (*decoder)(void *);
> > int inuse; /* Offset to metadata */
> > int align; /* Alignment */
> > int reserved; /* Reserved bytes at the end of slabs */
> > diff --git a/mm/slab_common.c b/mm/slab_common.c
> > index 3f3cd97..8c19bfd 100644
> > --- a/mm/slab_common.c
> > +++ b/mm/slab_common.c
> > @@ -193,6 +193,7 @@ kmem_cache_create_memcg(struct mem_cgroup *memcg, const char *name, size_t size,
> > s->object_size = s->size = size;
> > s->align = calculate_alignment(flags, align, size);
> > s->ctor = ctor;
> > + s->decoder = NULL;
> >
> > if (memcg_register_cache(memcg, s, parent_cache)) {
> > kmem_cache_free(kmem_cache, s);
> > @@ -248,7 +249,7 @@ kmem_cache_create(const char *name, size_t size, size_t align,
> > }
> > EXPORT_SYMBOL(kmem_cache_create);
> >
> > -void kmem_cache_destroy(struct kmem_cache *s)
> > +static void __kmem_cache_destroy(struct kmem_cache *s, void (*decoder)(void *))
> > {
> > /* Destroy all the children caches if we aren't a memcg cache */
> > kmem_cache_destroy_memcg_children(s);
> > @@ -259,6 +260,9 @@ void kmem_cache_destroy(struct kmem_cache *s)
> > if (!s->refcount) {
> > list_del(&s->list);
> >
> > + if (unlikely(decoder))
> > + s->decoder = decoder;
> > +
> > if (!__kmem_cache_shutdown(s)) {
> > mutex_unlock(&slab_mutex);
> > if (s->flags & SLAB_DESTROY_BY_RCU)
> > @@ -279,8 +283,19 @@ void kmem_cache_destroy(struct kmem_cache *s)
> > }
> > put_online_cpus();
> > }
> > +
> > +void kmem_cache_destroy(struct kmem_cache *s)
> > +{
> > + return __kmem_cache_destroy(s, NULL);
> > +}
> > EXPORT_SYMBOL(kmem_cache_destroy);
> >
> > +void kmem_cache_destroy_decoder(struct kmem_cache *s, void (*decoder)(void *))
> > +{
> > + return __kmem_cache_destroy(s, decoder);
> > +}
> > +EXPORT_SYMBOL(kmem_cache_destroy_decoder);
> > +
> > int slab_is_available(void)
> > {
> > return slab_state >= UP;
> > diff --git a/mm/slub.c b/mm/slub.c
> > index ba2ca53..34b3b75 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -3098,6 +3098,8 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page,
> > for_each_object(p, s, addr, page->objects) {
> >
> > if (!test_bit(slab_index(p, s, addr), map)) {
> > + if (unlikely(s->decoder))
> > + s->decoder(p);
> > printk(KERN_ERR "INFO: Object 0x%p @offset=%tu\n",
> > p, p - addr);
> > print_tracking(s, p);
> > --
> > 1.7.7.6
> >
> > --
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> > see: http://www.linux-mm.org/ .
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