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[v12] mm: slub: move sysfs slab alloc/free interfaces to debugfs

Message ID 1623438200-19361-1-git-send-email-faiyazm@codeaurora.org (mailing list archive)
State New
Headers show
Series [v12] mm: slub: move sysfs slab alloc/free interfaces to debugfs | expand

Commit Message

Faiyaz Mohammed June 11, 2021, 7:03 p.m. UTC
alloc_calls and free_calls implementation in sysfs have two issues,
one is PAGE_SIZE limitation of sysfs and other is it does not adhere
to "one value per file" rule.

To overcome this issues, move the alloc_calls and free_calls
implementation to debugfs.

Debugfs cache will be created if SLAB_STORE_USER flag is set.

Rename the alloc_calls/free_calls to alloc_traces/free_traces,
to be inline with what it does.

Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>
---
changes in v12:
	- To avoid confusion updated the patch version.

changes in v11:
	- https://lore.kernel.org/linux-mm/1623141934-7699-1-git-send-email-faiyazm@codeaurora.org/

changes in v10:
	- https://lore.kernel.org/linux-mm/1622996045-25826-1-git-send-email-faiyazm@codeaurora.org/

changes in v9:
	- https://lore.kernel.org/linux-mm/1622556633-29785-1-git-send-email-faiyazm@codeaurora.org/

changes in v8:
	- https://lore.kernel.org/linux-mm/1622542057-14632-1-git-send-email-faiyazm@codeaurora.org/

changes in V7:
	- https://lore.kernel.org/linux-mm/1621928285-751-1-git-send-email-faiyazm@codeaurora.org/

changes in v6:
	- https://lore.kernel.org/linux-mm/1621341949-26762-1-git-send-email-faiyazm@codeaurora.org/

changes in v5:
	- https://lore.kernel.org/linux-mm/1620296523-21922-1-git-send-email-faiyazm@codeaurora.org/

changes in v4:
	- https://lore.kernel.org/linux-mm/1618583239-18124-1-git-send-email-faiyazm@codeaurora.org/

changes in v3:
	- https://lore.kernel.org/linux-mm/1617712064-12264-1-git-send-email-faiyazm@codeaurora.org/

changes in v2:
	- https://lore.kernel.org/linux-mm/3ac1d3e6-6207-96ad-16a1-0f5139d8b2b5@codeaurora.org/

changes in v1
	- https://lore.kernel.org/linux-mm/1610443287-23933-1-git-send-email-faiyazm@codeaurora.org/

 mm/slab.h        |   6 ++
 mm/slab_common.c |   2 +
 mm/slub.c        | 283 +++++++++++++++++++++++++++++++++++++------------------
 3 files changed, 198 insertions(+), 93 deletions(-)

Comments

Qian Cai June 15, 2021, 3:58 p.m. UTC | #1
On 6/11/2021 3:03 PM, Faiyaz Mohammed wrote:
> alloc_calls and free_calls implementation in sysfs have two issues,
> one is PAGE_SIZE limitation of sysfs and other is it does not adhere
> to "one value per file" rule.
> 
> To overcome this issues, move the alloc_calls and free_calls
> implementation to debugfs.
> 
> Debugfs cache will be created if SLAB_STORE_USER flag is set.
> 
> Rename the alloc_calls/free_calls to alloc_traces/free_traces,
> to be inline with what it does.
> 
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>

Reverting this commit on today's linux-next fixed all leaks (hundreds) reported by kmemleak like below,

unreferenced object 0xffff00091ae1b540 (size 64):
  comm "lsbug", pid 1607, jiffies 4294958291 (age 1476.340s)
  hex dump (first 32 bytes):
    02 00 00 00 00 00 00 00 6b 6b 6b 6b 6b 6b 6b 6b  ........kkkkkkkk
    6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
  backtrace:
    [<ffff8000106b06b8>] slab_post_alloc_hook+0xa0/0x418
    [<ffff8000106b5c7c>] kmem_cache_alloc_trace+0x1e4/0x378
    [<ffff8000106b5e40>] slab_debugfs_start+0x30/0x50
    slab_debugfs_start at /usr/src/linux-next/mm/slub.c:5831
    [<ffff8000107b3dbc>] seq_read_iter+0x214/0xd50
    [<ffff8000107b4b84>] seq_read+0x28c/0x418
    [<ffff8000109560b4>] full_proxy_read+0xdc/0x148
    [<ffff800010738f24>] vfs_read+0x104/0x340
    [<ffff800010739ee0>] ksys_read+0xf8/0x1e0
    [<ffff80001073a03c>] __arm64_sys_read+0x74/0xa8
    [<ffff8000100358d4>] invoke_syscall.constprop.0+0xdc/0x1d8
    [<ffff800010035ab4>] do_el0_svc+0xe4/0x298
    [<ffff800011138528>] el0_svc+0x20/0x30
    [<ffff800011138b08>] el0t_64_sync_handler+0xb0/0xb8
    [<ffff80001001259c>] el0t_64_sync+0x178/0x17c

> ---
> changes in v12:
> 	- To avoid confusion updated the patch version.
> 
> changes in v11:
> 	- https://lore.kernel.org/linux-mm/1623141934-7699-1-git-send-email-faiyazm@codeaurora.org/
> 
> changes in v10:
> 	- https://lore.kernel.org/linux-mm/1622996045-25826-1-git-send-email-faiyazm@codeaurora.org/
> 
> changes in v9:
> 	- https://lore.kernel.org/linux-mm/1622556633-29785-1-git-send-email-faiyazm@codeaurora.org/
> 
> changes in v8:
> 	- https://lore.kernel.org/linux-mm/1622542057-14632-1-git-send-email-faiyazm@codeaurora.org/
> 
> changes in V7:
> 	- https://lore.kernel.org/linux-mm/1621928285-751-1-git-send-email-faiyazm@codeaurora.org/
> 
> changes in v6:
> 	- https://lore.kernel.org/linux-mm/1621341949-26762-1-git-send-email-faiyazm@codeaurora.org/
> 
> changes in v5:
> 	- https://lore.kernel.org/linux-mm/1620296523-21922-1-git-send-email-faiyazm@codeaurora.org/
> 
> changes in v4:
> 	- https://lore.kernel.org/linux-mm/1618583239-18124-1-git-send-email-faiyazm@codeaurora.org/
> 
> changes in v3:
> 	- https://lore.kernel.org/linux-mm/1617712064-12264-1-git-send-email-faiyazm@codeaurora.org/
> 
> changes in v2:
> 	- https://lore.kernel.org/linux-mm/3ac1d3e6-6207-96ad-16a1-0f5139d8b2b5@codeaurora.org/
> 
> changes in v1
> 	- https://lore.kernel.org/linux-mm/1610443287-23933-1-git-send-email-faiyazm@codeaurora.org/
> 
>  mm/slab.h        |   6 ++
>  mm/slab_common.c |   2 +
>  mm/slub.c        | 283 +++++++++++++++++++++++++++++++++++++------------------
>  3 files changed, 198 insertions(+), 93 deletions(-)
> 
> diff --git a/mm/slab.h b/mm/slab.h
> index 18c1927..60d4f4b 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -630,6 +630,12 @@ static inline bool slab_want_init_on_free(struct kmem_cache *c)
>  	return false;
>  }
>  
> +#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_SLUB_DEBUG)
> +void debugfs_slab_release(struct kmem_cache *);
> +#else
> +static inline void debugfs_slab_release(struct kmem_cache *s) { }
> +#endif
> +
>  #ifdef CONFIG_PRINTK
>  #define KS_ADDRS_COUNT 16
>  struct kmem_obj_info {
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index a4a5714..ee5456f 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -449,6 +449,7 @@ static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work)
>  	rcu_barrier();
>  
>  	list_for_each_entry_safe(s, s2, &to_destroy, list) {
> +		debugfs_slab_release(s);
>  		kfence_shutdown_cache(s);
>  #ifdef SLAB_SUPPORTS_SYSFS
>  		sysfs_slab_release(s);
> @@ -476,6 +477,7 @@ static int shutdown_cache(struct kmem_cache *s)
>  		schedule_work(&slab_caches_to_rcu_destroy_work);
>  	} else {
>  		kfence_shutdown_cache(s);
> +		debugfs_slab_release(s);
>  #ifdef SLAB_SUPPORTS_SYSFS
>  		sysfs_slab_unlink(s);
>  		sysfs_slab_release(s);
> diff --git a/mm/slub.c b/mm/slub.c
> index 3f96e09..ee0a357 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -36,6 +36,7 @@
>  #include <linux/memcontrol.h>
>  #include <linux/random.h>
>  
> +#include <linux/debugfs.h>
>  #include <trace/events/kmem.h>
>  
>  #include "internal.h"
> @@ -225,6 +226,12 @@ static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p)
>  							{ return 0; }
>  #endif
>  
> +#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_SLUB_DEBUG)
> +static void debugfs_slab_add(struct kmem_cache *);
> +#else
> +static inline void debugfs_slab_add(struct kmem_cache *s) { }
> +#endif
> +
>  static inline void stat(const struct kmem_cache *s, enum stat_item si)
>  {
>  #ifdef CONFIG_SLUB_STATS
> @@ -4546,6 +4553,9 @@ int __kmem_cache_create(struct kmem_cache *s, slab_flags_t flags)
>  	if (err)
>  		__kmem_cache_release(s);
>  
> +	if (s->flags & SLAB_STORE_USER)
> +		debugfs_slab_add(s);
> +
>  	return err;
>  }
>  
> @@ -4686,6 +4696,8 @@ static long validate_slab_cache(struct kmem_cache *s)
>  
>  	return count;
>  }
> +
> +#ifdef CONFIG_DEBUG_FS
>  /*
>   * Generate lists of code addresses where slabcache objects are allocated
>   * and freed.
> @@ -4709,6 +4721,8 @@ struct loc_track {
>  	struct location *loc;
>  };
>  
> +static struct dentry *slab_debugfs_root;
> +
>  static void free_loc_track(struct loc_track *t)
>  {
>  	if (t->max)
> @@ -4825,82 +4839,7 @@ static void process_slab(struct loc_track *t, struct kmem_cache *s,
>  			add_location(t, s, get_track(s, p, alloc));
>  	put_map(map);
>  }
> -
> -static int list_locations(struct kmem_cache *s, char *buf,
> -			  enum track_item alloc)
> -{
> -	int len = 0;
> -	unsigned long i;
> -	struct loc_track t = { 0, 0, NULL };
> -	int node;
> -	struct kmem_cache_node *n;
> -
> -	if (!alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location),
> -			     GFP_KERNEL)) {
> -		return sysfs_emit(buf, "Out of memory\n");
> -	}
> -	/* Push back cpu slabs */
> -	flush_all(s);
> -
> -	for_each_kmem_cache_node(s, node, n) {
> -		unsigned long flags;
> -		struct page *page;
> -
> -		if (!atomic_long_read(&n->nr_slabs))
> -			continue;
> -
> -		spin_lock_irqsave(&n->list_lock, flags);
> -		list_for_each_entry(page, &n->partial, slab_list)
> -			process_slab(&t, s, page, alloc);
> -		list_for_each_entry(page, &n->full, slab_list)
> -			process_slab(&t, s, page, alloc);
> -		spin_unlock_irqrestore(&n->list_lock, flags);
> -	}
> -
> -	for (i = 0; i < t.count; i++) {
> -		struct location *l = &t.loc[i];
> -
> -		len += sysfs_emit_at(buf, len, "%7ld ", l->count);
> -
> -		if (l->addr)
> -			len += sysfs_emit_at(buf, len, "%pS", (void *)l->addr);
> -		else
> -			len += sysfs_emit_at(buf, len, "<not-available>");
> -
> -		if (l->sum_time != l->min_time)
> -			len += sysfs_emit_at(buf, len, " age=%ld/%ld/%ld",
> -					     l->min_time,
> -					     (long)div_u64(l->sum_time,
> -							   l->count),
> -					     l->max_time);
> -		else
> -			len += sysfs_emit_at(buf, len, " age=%ld", l->min_time);
> -
> -		if (l->min_pid != l->max_pid)
> -			len += sysfs_emit_at(buf, len, " pid=%ld-%ld",
> -					     l->min_pid, l->max_pid);
> -		else
> -			len += sysfs_emit_at(buf, len, " pid=%ld",
> -					     l->min_pid);
> -
> -		if (num_online_cpus() > 1 &&
> -		    !cpumask_empty(to_cpumask(l->cpus)))
> -			len += sysfs_emit_at(buf, len, " cpus=%*pbl",
> -					     cpumask_pr_args(to_cpumask(l->cpus)));
> -
> -		if (nr_online_nodes > 1 && !nodes_empty(l->nodes))
> -			len += sysfs_emit_at(buf, len, " nodes=%*pbl",
> -					     nodemask_pr_args(&l->nodes));
> -
> -		len += sysfs_emit_at(buf, len, "\n");
> -	}
> -
> -	free_loc_track(&t);
> -	if (!t.count)
> -		len += sysfs_emit_at(buf, len, "No data\n");
> -
> -	return len;
> -}
> +#endif  /* CONFIG_DEBUG_FS   */
>  #endif	/* CONFIG_SLUB_DEBUG */
>  
>  #ifdef SLUB_RESILIENCY_TEST
> @@ -5350,21 +5289,6 @@ static ssize_t validate_store(struct kmem_cache *s,
>  }
>  SLAB_ATTR(validate);
>  
> -static ssize_t alloc_calls_show(struct kmem_cache *s, char *buf)
> -{
> -	if (!(s->flags & SLAB_STORE_USER))
> -		return -ENOSYS;
> -	return list_locations(s, buf, TRACK_ALLOC);
> -}
> -SLAB_ATTR_RO(alloc_calls);
> -
> -static ssize_t free_calls_show(struct kmem_cache *s, char *buf)
> -{
> -	if (!(s->flags & SLAB_STORE_USER))
> -		return -ENOSYS;
> -	return list_locations(s, buf, TRACK_FREE);
> -}
> -SLAB_ATTR_RO(free_calls);
>  #endif /* CONFIG_SLUB_DEBUG */
>  
>  #ifdef CONFIG_FAILSLAB
> @@ -5528,8 +5452,6 @@ static struct attribute *slab_attrs[] = {
>  	&poison_attr.attr,
>  	&store_user_attr.attr,
>  	&validate_attr.attr,
> -	&alloc_calls_attr.attr,
> -	&free_calls_attr.attr,
>  #endif
>  #ifdef CONFIG_ZONE_DMA
>  	&cache_dma_attr.attr,
> @@ -5818,6 +5740,181 @@ static int __init slab_sysfs_init(void)
>  __initcall(slab_sysfs_init);
>  #endif /* CONFIG_SYSFS */
>  
> +#if defined(CONFIG_SLUB_DEBUG) && defined(CONFIG_DEBUG_FS)
> +static int slab_debugfs_show(struct seq_file *seq, void *v)
> +{
> +
> +	struct location *l;
> +	unsigned int idx = *(unsigned int *)v;
> +	struct loc_track *t = seq->private;
> +
> +	if (idx < t->count) {
> +		l = &t->loc[idx];
> +
> +		seq_printf(seq, "%7ld ", l->count);
> +
> +		if (l->addr)
> +			seq_printf(seq, "%pS", (void *)l->addr);
> +		else
> +			seq_puts(seq, "<not-available>");
> +
> +		if (l->sum_time != l->min_time) {
> +			seq_printf(seq, " age=%ld/%llu/%ld",
> +				l->min_time, div_u64(l->sum_time, l->count),
> +				l->max_time);
> +		} else
> +			seq_printf(seq, " age=%ld", l->min_time);
> +
> +		if (l->min_pid != l->max_pid)
> +			seq_printf(seq, " pid=%ld-%ld", l->min_pid, l->max_pid);
> +		else
> +			seq_printf(seq, " pid=%ld",
> +				l->min_pid);
> +
> +		if (num_online_cpus() > 1 && !cpumask_empty(to_cpumask(l->cpus)))
> +			seq_printf(seq, " cpus=%*pbl",
> +				 cpumask_pr_args(to_cpumask(l->cpus)));
> +
> +		if (nr_online_nodes > 1 && !nodes_empty(l->nodes))
> +			seq_printf(seq, " nodes=%*pbl",
> +				 nodemask_pr_args(&l->nodes));
> +
> +		seq_puts(seq, "\n");
> +	}
> +
> +	if (!idx && !t->count)
> +		seq_puts(seq, "No data\n");
> +
> +	return 0;
> +}
> +
> +static void slab_debugfs_stop(struct seq_file *seq, void *v)
> +{
> +	kfree(v);
> +}
> +
> +static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos)
> +{
> +	loff_t *spos = v;
> +	struct loc_track *t = seq->private;
> +
> +	if (*ppos < t->count) {
> +		*ppos = ++*spos;
> +		return spos;
> +	}
> +	*ppos = ++*spos;
> +	return NULL;
> +}
> +
> +static void *slab_debugfs_start(struct seq_file *seq, loff_t *ppos)
> +{
> +	loff_t *spos = kmalloc(sizeof(loff_t), GFP_KERNEL);
> +
> +	if (!spos)
> +		return NULL;
> +
> +	*spos = *ppos;
> +	return spos;
> +}
> +
> +static const struct seq_operations slab_debugfs_sops = {
> +	.start  = slab_debugfs_start,
> +	.next   = slab_debugfs_next,
> +	.stop   = slab_debugfs_stop,
> +	.show   = slab_debugfs_show,
> +};
> +
> +static int slab_debug_trace_open(struct inode *inode, struct file *filep)
> +{
> +
> +	struct kmem_cache_node *n;
> +	enum track_item alloc;
> +	int node;
> +	struct loc_track *t = __seq_open_private(filep, &slab_debugfs_sops,
> +						sizeof(struct loc_track));
> +	struct kmem_cache *s = file_inode(filep)->i_private;
> +
> +	if (strcmp(filep->f_path.dentry->d_name.name, "alloc_traces") == 0)
> +		alloc = TRACK_ALLOC;
> +	else
> +		alloc = TRACK_FREE;
> +
> +	if (!alloc_loc_track(t, PAGE_SIZE / sizeof(struct location), GFP_KERNEL))
> +		return -ENOMEM;
> +
> +	/* Push back cpu slabs */
> +	flush_all(s);
> +
> +	for_each_kmem_cache_node(s, node, n) {
> +		unsigned long flags;
> +		struct page *page;
> +
> +		if (!atomic_long_read(&n->nr_slabs))
> +			continue;
> +
> +		spin_lock_irqsave(&n->list_lock, flags);
> +		list_for_each_entry(page, &n->partial, slab_list)
> +			process_slab(t, s, page, alloc);
> +		list_for_each_entry(page, &n->full, slab_list)
> +			process_slab(t, s, page, alloc);
> +		spin_unlock_irqrestore(&n->list_lock, flags);
> +	}
> +
> +	return 0;
> +}
> +
> +static int slab_debug_trace_release(struct inode *inode, struct file *file)
> +{
> +	struct seq_file *seq = file->private_data;
> +	struct loc_track *t = seq->private;
> +
> +	free_loc_track(t);
> +	return seq_release_private(inode, file);
> +}
> +
> +static const struct file_operations slab_debugfs_fops = {
> +	.open    = slab_debug_trace_open,
> +	.read    = seq_read,
> +	.llseek  = seq_lseek,
> +	.release = slab_debug_trace_release,
> +};
> +
> +static void debugfs_slab_add(struct kmem_cache *s)
> +{
> +	struct dentry *slab_cache_dir;
> +
> +	if (unlikely(!slab_debugfs_root))
> +		return;
> +
> +	slab_cache_dir = debugfs_create_dir(s->name, slab_debugfs_root);
> +
> +	debugfs_create_file("alloc_traces", 0400,
> +		slab_cache_dir, s, &slab_debugfs_fops);
> +
> +	debugfs_create_file("free_traces", 0400,
> +		slab_cache_dir, s, &slab_debugfs_fops);
> +}
> +
> +void debugfs_slab_release(struct kmem_cache *s)
> +{
> +	debugfs_remove_recursive(debugfs_lookup(s->name, slab_debugfs_root));
> +}
> +
> +static int __init slab_debugfs_init(void)
> +{
> +	struct kmem_cache *s;
> +
> +	slab_debugfs_root = debugfs_create_dir("slab", NULL);
> +
> +	list_for_each_entry(s, &slab_caches, list)
> +		if (s->flags & SLAB_STORE_USER)
> +			debugfs_slab_add(s);
> +
> +	return 0;
> +
> +}
> +__initcall(slab_debugfs_init);
> +#endif
>  /*
>   * The /proc/slabinfo ABI
>   */
>
Vlastimil Babka June 16, 2021, 11:05 a.m. UTC | #2
On 6/15/21 5:58 PM, Qian Cai wrote:
> 
> 
> On 6/11/2021 3:03 PM, Faiyaz Mohammed wrote:
>> alloc_calls and free_calls implementation in sysfs have two issues,
>> one is PAGE_SIZE limitation of sysfs and other is it does not adhere
>> to "one value per file" rule.
>> 
>> To overcome this issues, move the alloc_calls and free_calls
>> implementation to debugfs.
>> 
>> Debugfs cache will be created if SLAB_STORE_USER flag is set.
>> 
>> Rename the alloc_calls/free_calls to alloc_traces/free_traces,
>> to be inline with what it does.
>> 
>> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
>> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Signed-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>
> 
> Reverting this commit on today's linux-next fixed all leaks (hundreds) reported by kmemleak like below,
> 
> unreferenced object 0xffff00091ae1b540 (size 64):
>   comm "lsbug", pid 1607, jiffies 4294958291 (age 1476.340s)
>   hex dump (first 32 bytes):
>     02 00 00 00 00 00 00 00 6b 6b 6b 6b 6b 6b 6b 6b  ........kkkkkkkk
>     6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
>   backtrace:
>     [<ffff8000106b06b8>] slab_post_alloc_hook+0xa0/0x418
>     [<ffff8000106b5c7c>] kmem_cache_alloc_trace+0x1e4/0x378
>     [<ffff8000106b5e40>] slab_debugfs_start+0x30/0x50
>     slab_debugfs_start at /usr/src/linux-next/mm/slub.c:5831
>     [<ffff8000107b3dbc>] seq_read_iter+0x214/0xd50
>     [<ffff8000107b4b84>] seq_read+0x28c/0x418
>     [<ffff8000109560b4>] full_proxy_read+0xdc/0x148
>     [<ffff800010738f24>] vfs_read+0x104/0x340
>     [<ffff800010739ee0>] ksys_read+0xf8/0x1e0
>     [<ffff80001073a03c>] __arm64_sys_read+0x74/0xa8
>     [<ffff8000100358d4>] invoke_syscall.constprop.0+0xdc/0x1d8
>     [<ffff800010035ab4>] do_el0_svc+0xe4/0x298
>     [<ffff800011138528>] el0_svc+0x20/0x30
>     [<ffff800011138b08>] el0t_64_sync_handler+0xb0/0xb8
>     [<ffff80001001259c>] el0t_64_sync+0x178/0x17c
> 

I think the problem is here:

>> +static void slab_debugfs_stop(struct seq_file *seq, void *v)
>> +{
>> +	kfree(v);
>> +}
>> +
>> +static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos)
>> +{
>> +	loff_t *spos = v;
>> +	struct loc_track *t = seq->private;
>> +
>> +	if (*ppos < t->count) {
>> +		*ppos = ++*spos;
>> +		return spos;
>> +	}
>> +	*ppos = ++*spos;
>> +	return NULL;
>> +}

If we return NULL, then NULL is passed to slab_debugfs_stop and thus we don't
kfree ppos. kfree(NULL) is silently ignored.

I think as we have private struct loc_track, we can add a pos field there and
avoid the kmaloc/kfree altogether.
Faiyaz Mohammed June 16, 2021, 3:50 p.m. UTC | #3
On 6/16/2021 4:35 PM, Vlastimil Babka wrote:
> On 6/15/21 5:58 PM, Qian Cai wrote:
>>
>>
>> On 6/11/2021 3:03 PM, Faiyaz Mohammed wrote:
>>> alloc_calls and free_calls implementation in sysfs have two issues,
>>> one is PAGE_SIZE limitation of sysfs and other is it does not adhere
>>> to "one value per file" rule.
>>>
>>> To overcome this issues, move the alloc_calls and free_calls
>>> implementation to debugfs.
>>>
>>> Debugfs cache will be created if SLAB_STORE_USER flag is set.
>>>
>>> Rename the alloc_calls/free_calls to alloc_traces/free_traces,
>>> to be inline with what it does.
>>>
>>> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
>>> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>> Signed-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>
>>
>> Reverting this commit on today's linux-next fixed all leaks (hundreds) reported by kmemleak like below,
>>
>> unreferenced object 0xffff00091ae1b540 (size 64):
>>   comm "lsbug", pid 1607, jiffies 4294958291 (age 1476.340s)
>>   hex dump (first 32 bytes):
>>     02 00 00 00 00 00 00 00 6b 6b 6b 6b 6b 6b 6b 6b  ........kkkkkkkk
>>     6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
>>   backtrace:
>>     [<ffff8000106b06b8>] slab_post_alloc_hook+0xa0/0x418
>>     [<ffff8000106b5c7c>] kmem_cache_alloc_trace+0x1e4/0x378
>>     [<ffff8000106b5e40>] slab_debugfs_start+0x30/0x50
>>     slab_debugfs_start at /usr/src/linux-next/mm/slub.c:5831
>>     [<ffff8000107b3dbc>] seq_read_iter+0x214/0xd50
>>     [<ffff8000107b4b84>] seq_read+0x28c/0x418
>>     [<ffff8000109560b4>] full_proxy_read+0xdc/0x148
>>     [<ffff800010738f24>] vfs_read+0x104/0x340
>>     [<ffff800010739ee0>] ksys_read+0xf8/0x1e0
>>     [<ffff80001073a03c>] __arm64_sys_read+0x74/0xa8
>>     [<ffff8000100358d4>] invoke_syscall.constprop.0+0xdc/0x1d8
>>     [<ffff800010035ab4>] do_el0_svc+0xe4/0x298
>>     [<ffff800011138528>] el0_svc+0x20/0x30
>>     [<ffff800011138b08>] el0t_64_sync_handler+0xb0/0xb8
>>     [<ffff80001001259c>] el0t_64_sync+0x178/0x17c
>>
> 
> I think the problem is here:
> 
>>> +static void slab_debugfs_stop(struct seq_file *seq, void *v)
>>> +{
>>> +	kfree(v);
>>> +}
>>> +
>>> +static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos)
>>> +{
>>> +	loff_t *spos = v;
>>> +	struct loc_track *t = seq->private;
>>> +
>>> +	if (*ppos < t->count) {
>>> +		*ppos = ++*spos;
>>> +		return spos;
>>> +	}
>>> +	*ppos = ++*spos;
>>> +	return NULL;
>>> +}
> 
> If we return NULL, then NULL is passed to slab_debugfs_stop and thus we don't
> kfree ppos. kfree(NULL) is silently ignored.
> 
I think yes, if NULL passed to kfree, it simply do return.
> I think as we have private struct loc_track, we can add a pos field there and
> avoid the kmaloc/kfree altogether.
> 
Hmm, yes we can add pos field "or" we can use argument "v" mean we can
update v with pos in ->next() and use in ->show() to avoid the leak
(kmalloc/kfree).


Thanks and regards,
Mohammed Faiyaz
Vlastimil Babka June 16, 2021, 4:17 p.m. UTC | #4
On 6/16/21 5:50 PM, Faiyaz Mohammed wrote:
> 
> 
> On 6/16/2021 4:35 PM, Vlastimil Babka wrote:
>> On 6/15/21 5:58 PM, Qian Cai wrote:
>>>
>>>
>>> On 6/11/2021 3:03 PM, Faiyaz Mohammed wrote:
>>>> alloc_calls and free_calls implementation in sysfs have two issues,
>>>> one is PAGE_SIZE limitation of sysfs and other is it does not adhere
>>>> to "one value per file" rule.
>>>>
>>>> To overcome this issues, move the alloc_calls and free_calls
>>>> implementation to debugfs.
>>>>
>>>> Debugfs cache will be created if SLAB_STORE_USER flag is set.
>>>>
>>>> Rename the alloc_calls/free_calls to alloc_traces/free_traces,
>>>> to be inline with what it does.
>>>>
>>>> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
>>>> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>>> Signed-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>
>>>
>>> Reverting this commit on today's linux-next fixed all leaks (hundreds) reported by kmemleak like below,
>>>
>>> unreferenced object 0xffff00091ae1b540 (size 64):
>>>   comm "lsbug", pid 1607, jiffies 4294958291 (age 1476.340s)
>>>   hex dump (first 32 bytes):
>>>     02 00 00 00 00 00 00 00 6b 6b 6b 6b 6b 6b 6b 6b  ........kkkkkkkk
>>>     6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
>>>   backtrace:
>>>     [<ffff8000106b06b8>] slab_post_alloc_hook+0xa0/0x418
>>>     [<ffff8000106b5c7c>] kmem_cache_alloc_trace+0x1e4/0x378
>>>     [<ffff8000106b5e40>] slab_debugfs_start+0x30/0x50
>>>     slab_debugfs_start at /usr/src/linux-next/mm/slub.c:5831
>>>     [<ffff8000107b3dbc>] seq_read_iter+0x214/0xd50
>>>     [<ffff8000107b4b84>] seq_read+0x28c/0x418
>>>     [<ffff8000109560b4>] full_proxy_read+0xdc/0x148
>>>     [<ffff800010738f24>] vfs_read+0x104/0x340
>>>     [<ffff800010739ee0>] ksys_read+0xf8/0x1e0
>>>     [<ffff80001073a03c>] __arm64_sys_read+0x74/0xa8
>>>     [<ffff8000100358d4>] invoke_syscall.constprop.0+0xdc/0x1d8
>>>     [<ffff800010035ab4>] do_el0_svc+0xe4/0x298
>>>     [<ffff800011138528>] el0_svc+0x20/0x30
>>>     [<ffff800011138b08>] el0t_64_sync_handler+0xb0/0xb8
>>>     [<ffff80001001259c>] el0t_64_sync+0x178/0x17c
>>>
>> 
>> I think the problem is here:
>> 
>>>> +static void slab_debugfs_stop(struct seq_file *seq, void *v)
>>>> +{
>>>> +	kfree(v);
>>>> +}
>>>> +
>>>> +static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos)
>>>> +{
>>>> +	loff_t *spos = v;
>>>> +	struct loc_track *t = seq->private;
>>>> +
>>>> +	if (*ppos < t->count) {
>>>> +		*ppos = ++*spos;
>>>> +		return spos;
>>>> +	}
>>>> +	*ppos = ++*spos;
>>>> +	return NULL;
>>>> +}
>> 
>> If we return NULL, then NULL is passed to slab_debugfs_stop and thus we don't
>> kfree ppos. kfree(NULL) is silently ignored.
>> 
> I think yes, if NULL passed to kfree, it simply do return.
>> I think as we have private struct loc_track, we can add a pos field there and
>> avoid the kmaloc/kfree altogether.
>> 
> Hmm, yes we can add pos field "or" we can use argument "v" mean we can
> update v with pos in ->next() and use in ->show() to avoid the leak
> (kmalloc/kfree).

Can you explain the "or" part more. It's exactly what we already do, no? We use
"v" as you said. The problem is, if next(); returns NULL, then stop() gets the
NULL as "v". It's just what I see in the code of seq_read_iter() and traverse()
in fs/seq_file.c. I don't see another way to say there are no more records to
print - only to return NULL in next().
Ah, ok so we could maybe do the kfree() in next() then before returning NULL,
which is the last moment we have the pointer. But really, if we already have a
loc_track in private, why kmalloc an additional loff_t.

Anyway it seems to me also that
Documentation/filesystems/seq_file.rst should be updated, as the kfree() in
stop() is exactly what it suggests, and it doesn't show how next() indicates
that there are no more records by returning NULL, and what to do about kfree() then.
Faiyaz Mohammed June 17, 2021, 6:32 a.m. UTC | #5
On 6/16/2021 9:47 PM, Vlastimil Babka wrote:
> On 6/16/21 5:50 PM, Faiyaz Mohammed wrote:
>>
>>
>> On 6/16/2021 4:35 PM, Vlastimil Babka wrote:
>>> On 6/15/21 5:58 PM, Qian Cai wrote:
>>>>
>>>>
>>>> On 6/11/2021 3:03 PM, Faiyaz Mohammed wrote:
>>>>> alloc_calls and free_calls implementation in sysfs have two issues,
>>>>> one is PAGE_SIZE limitation of sysfs and other is it does not adhere
>>>>> to "one value per file" rule.
>>>>>
>>>>> To overcome this issues, move the alloc_calls and free_calls
>>>>> implementation to debugfs.
>>>>>
>>>>> Debugfs cache will be created if SLAB_STORE_USER flag is set.
>>>>>
>>>>> Rename the alloc_calls/free_calls to alloc_traces/free_traces,
>>>>> to be inline with what it does.
>>>>>
>>>>> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
>>>>> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>>>> Signed-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>
>>>>
>>>> Reverting this commit on today's linux-next fixed all leaks (hundreds) reported by kmemleak like below,
>>>>
>>>> unreferenced object 0xffff00091ae1b540 (size 64):
>>>>   comm "lsbug", pid 1607, jiffies 4294958291 (age 1476.340s)
>>>>   hex dump (first 32 bytes):
>>>>     02 00 00 00 00 00 00 00 6b 6b 6b 6b 6b 6b 6b 6b  ........kkkkkkkk
>>>>     6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
>>>>   backtrace:
>>>>     [<ffff8000106b06b8>] slab_post_alloc_hook+0xa0/0x418
>>>>     [<ffff8000106b5c7c>] kmem_cache_alloc_trace+0x1e4/0x378
>>>>     [<ffff8000106b5e40>] slab_debugfs_start+0x30/0x50
>>>>     slab_debugfs_start at /usr/src/linux-next/mm/slub.c:5831
>>>>     [<ffff8000107b3dbc>] seq_read_iter+0x214/0xd50
>>>>     [<ffff8000107b4b84>] seq_read+0x28c/0x418
>>>>     [<ffff8000109560b4>] full_proxy_read+0xdc/0x148
>>>>     [<ffff800010738f24>] vfs_read+0x104/0x340
>>>>     [<ffff800010739ee0>] ksys_read+0xf8/0x1e0
>>>>     [<ffff80001073a03c>] __arm64_sys_read+0x74/0xa8
>>>>     [<ffff8000100358d4>] invoke_syscall.constprop.0+0xdc/0x1d8
>>>>     [<ffff800010035ab4>] do_el0_svc+0xe4/0x298
>>>>     [<ffff800011138528>] el0_svc+0x20/0x30
>>>>     [<ffff800011138b08>] el0t_64_sync_handler+0xb0/0xb8
>>>>     [<ffff80001001259c>] el0t_64_sync+0x178/0x17c
>>>>
>>>
>>> I think the problem is here:
>>>
>>>>> +static void slab_debugfs_stop(struct seq_file *seq, void *v)
>>>>> +{
>>>>> +	kfree(v);
>>>>> +}
>>>>> +
>>>>> +static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos)
>>>>> +{
>>>>> +	loff_t *spos = v;
>>>>> +	struct loc_track *t = seq->private;
>>>>> +
>>>>> +	if (*ppos < t->count) {
>>>>> +		*ppos = ++*spos;
>>>>> +		return spos;
>>>>> +	}
>>>>> +	*ppos = ++*spos;
>>>>> +	return NULL;
>>>>> +}
>>>
>>> If we return NULL, then NULL is passed to slab_debugfs_stop and thus we don't
>>> kfree ppos. kfree(NULL) is silently ignored.
>>>
>> I think yes, if NULL passed to kfree, it simply do return.
>>> I think as we have private struct loc_track, we can add a pos field there and
>>> avoid the kmaloc/kfree altogether.
>>>
>> Hmm, yes we can add pos field "or" we can use argument "v" mean we can
>> update v with pos in ->next() and use in ->show() to avoid the leak
>> (kmalloc/kfree).
> 
> Can you explain the "or" part more. It's exactly what we already do, no?I am thinking if we simplly do ppos return from slab_debugfs_start() and
in slab_debugfs_next() assign ppos to "v", update it and return if
records are there. something like below (approach 1):
...
static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos)
{
...
        v = ppos;
        if (*ppos < t->count) {
                 ++*ppos;
                return v;
        }

        ++*ppos;
        return NULL;
}
...
static void *slab_debugfs_start(struct seq_file *seq, loff_t *ppos)
{
        return ppos;
}
...

> "v" as you said. The problem is, if next(); returns NULL, then stop() gets the
> NULL as "v". It's just what I see in the code of seq_read_iter() and traverse()
> in fs/seq_file.c. I don't see another way to say there are no more records to
> print - only to return NULL in next().
> Ah, ok so we could maybe do the kfree() in next() then before returning NULL,
> which is the last moment we have the pointer. But really, if we already have a
> loc_track in private, why kmalloc an additional loff_t.
> 
Yes, we can do kfree() before returning NULL, but better to add ppos in
lock_track. (approach 2)

> Anyway it seems to me also that
> Documentation/filesystems/seq_file.rst should be updated, as the kfree() in
> stop() is exactly what it suggests, and it doesn't show how next() indicates
> that there are no more records by returning NULL, and what to do about kfree() then.

Can you please suggest me which approach would be good to avoid the
leak?. I will update in next patch version.
Vlastimil Babka June 17, 2021, 2:52 p.m. UTC | #6
On 6/17/21 8:32 AM, Faiyaz Mohammed wrote:
> 
> 
> On 6/16/2021 9:47 PM, Vlastimil Babka wrote:
>> On 6/16/21 5:50 PM, Faiyaz Mohammed wrote:
>>>
>>>
>>> On 6/16/2021 4:35 PM, Vlastimil Babka wrote:
>>>> On 6/15/21 5:58 PM, Qian Cai wrote:
>>>>>
>>>>>
>>>>> On 6/11/2021 3:03 PM, Faiyaz Mohammed wrote:
>>>>>> alloc_calls and free_calls implementation in sysfs have two issues,
>>>>>> one is PAGE_SIZE limitation of sysfs and other is it does not adhere
>>>>>> to "one value per file" rule.
>>>>>>
>>>>>> To overcome this issues, move the alloc_calls and free_calls
>>>>>> implementation to debugfs.
>>>>>>
>>>>>> Debugfs cache will be created if SLAB_STORE_USER flag is set.
>>>>>>
>>>>>> Rename the alloc_calls/free_calls to alloc_traces/free_traces,
>>>>>> to be inline with what it does.
>>>>>>
>>>>>> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
>>>>>> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>>>>> Signed-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>
>>>>>
>>>>> Reverting this commit on today's linux-next fixed all leaks (hundreds) reported by kmemleak like below,
>>>>>
>>>>> unreferenced object 0xffff00091ae1b540 (size 64):
>>>>>   comm "lsbug", pid 1607, jiffies 4294958291 (age 1476.340s)
>>>>>   hex dump (first 32 bytes):
>>>>>     02 00 00 00 00 00 00 00 6b 6b 6b 6b 6b 6b 6b 6b  ........kkkkkkkk
>>>>>     6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
>>>>>   backtrace:
>>>>>     [<ffff8000106b06b8>] slab_post_alloc_hook+0xa0/0x418
>>>>>     [<ffff8000106b5c7c>] kmem_cache_alloc_trace+0x1e4/0x378
>>>>>     [<ffff8000106b5e40>] slab_debugfs_start+0x30/0x50
>>>>>     slab_debugfs_start at /usr/src/linux-next/mm/slub.c:5831
>>>>>     [<ffff8000107b3dbc>] seq_read_iter+0x214/0xd50
>>>>>     [<ffff8000107b4b84>] seq_read+0x28c/0x418
>>>>>     [<ffff8000109560b4>] full_proxy_read+0xdc/0x148
>>>>>     [<ffff800010738f24>] vfs_read+0x104/0x340
>>>>>     [<ffff800010739ee0>] ksys_read+0xf8/0x1e0
>>>>>     [<ffff80001073a03c>] __arm64_sys_read+0x74/0xa8
>>>>>     [<ffff8000100358d4>] invoke_syscall.constprop.0+0xdc/0x1d8
>>>>>     [<ffff800010035ab4>] do_el0_svc+0xe4/0x298
>>>>>     [<ffff800011138528>] el0_svc+0x20/0x30
>>>>>     [<ffff800011138b08>] el0t_64_sync_handler+0xb0/0xb8
>>>>>     [<ffff80001001259c>] el0t_64_sync+0x178/0x17c
>>>>>
>>>>
>>>> I think the problem is here:
>>>>
>>>>>> +static void slab_debugfs_stop(struct seq_file *seq, void *v)
>>>>>> +{
>>>>>> +	kfree(v);
>>>>>> +}
>>>>>> +
>>>>>> +static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos)
>>>>>> +{
>>>>>> +	loff_t *spos = v;
>>>>>> +	struct loc_track *t = seq->private;
>>>>>> +
>>>>>> +	if (*ppos < t->count) {
>>>>>> +		*ppos = ++*spos;
>>>>>> +		return spos;
>>>>>> +	}
>>>>>> +	*ppos = ++*spos;
>>>>>> +	return NULL;
>>>>>> +}
>>>>
>>>> If we return NULL, then NULL is passed to slab_debugfs_stop and thus we don't
>>>> kfree ppos. kfree(NULL) is silently ignored.
>>>>
>>> I think yes, if NULL passed to kfree, it simply do return.
>>>> I think as we have private struct loc_track, we can add a pos field there and
>>>> avoid the kmaloc/kfree altogether.
>>>>
>>> Hmm, yes we can add pos field "or" we can use argument "v" mean we can
>>> update v with pos in ->next() and use in ->show() to avoid the leak
>>> (kmalloc/kfree).
>> 
>> Can you explain the "or" part more. It's exactly what we already do, no?I am thinking if we simplly do ppos return from slab_debugfs_start() and
> in slab_debugfs_next() assign ppos to "v", update it and return if
> records are there. something like below (approach 1):
> ...
> static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos)
> {
> ...
>         v = ppos;
>         if (*ppos < t->count) {
>                  ++*ppos;
>                 return v;
>         }
> 
>         ++*ppos;
>         return NULL;
> }
> ...
> static void *slab_debugfs_start(struct seq_file *seq, loff_t *ppos)
> {
>         return ppos;
> }

OK maybe that works too. Bonus points if some other code does that. And then it
might be another reason to update the Documentation file.

> ...
> 
>> "v" as you said. The problem is, if next(); returns NULL, then stop() gets the
>> NULL as "v". It's just what I see in the code of seq_read_iter() and traverse()
>> in fs/seq_file.c. I don't see another way to say there are no more records to
>> print - only to return NULL in next().
>> Ah, ok so we could maybe do the kfree() in next() then before returning NULL,
>> which is the last moment we have the pointer. But really, if we already have a
>> loc_track in private, why kmalloc an additional loff_t.
>> 
> Yes, we can do kfree() before returning NULL, but better to add ppos in
> lock_track. (approach 2)
> 
>> Anyway it seems to me also that
>> Documentation/filesystems/seq_file.rst should be updated, as the kfree() in
>> stop() is exactly what it suggests, and it doesn't show how next() indicates
>> that there are no more records by returning NULL, and what to do about kfree() then.
> 
> Can you please suggest me which approach would be good to avoid the
> leak?. I will update in next patch version.

I guess your approach is simpler as we don't track two pos variables.
diff mbox series

Patch

diff --git a/mm/slab.h b/mm/slab.h
index 18c1927..60d4f4b 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -630,6 +630,12 @@  static inline bool slab_want_init_on_free(struct kmem_cache *c)
 	return false;
 }
 
+#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_SLUB_DEBUG)
+void debugfs_slab_release(struct kmem_cache *);
+#else
+static inline void debugfs_slab_release(struct kmem_cache *s) { }
+#endif
+
 #ifdef CONFIG_PRINTK
 #define KS_ADDRS_COUNT 16
 struct kmem_obj_info {
diff --git a/mm/slab_common.c b/mm/slab_common.c
index a4a5714..ee5456f 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -449,6 +449,7 @@  static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work)
 	rcu_barrier();
 
 	list_for_each_entry_safe(s, s2, &to_destroy, list) {
+		debugfs_slab_release(s);
 		kfence_shutdown_cache(s);
 #ifdef SLAB_SUPPORTS_SYSFS
 		sysfs_slab_release(s);
@@ -476,6 +477,7 @@  static int shutdown_cache(struct kmem_cache *s)
 		schedule_work(&slab_caches_to_rcu_destroy_work);
 	} else {
 		kfence_shutdown_cache(s);
+		debugfs_slab_release(s);
 #ifdef SLAB_SUPPORTS_SYSFS
 		sysfs_slab_unlink(s);
 		sysfs_slab_release(s);
diff --git a/mm/slub.c b/mm/slub.c
index 3f96e09..ee0a357 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -36,6 +36,7 @@ 
 #include <linux/memcontrol.h>
 #include <linux/random.h>
 
+#include <linux/debugfs.h>
 #include <trace/events/kmem.h>
 
 #include "internal.h"
@@ -225,6 +226,12 @@  static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p)
 							{ return 0; }
 #endif
 
+#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_SLUB_DEBUG)
+static void debugfs_slab_add(struct kmem_cache *);
+#else
+static inline void debugfs_slab_add(struct kmem_cache *s) { }
+#endif
+
 static inline void stat(const struct kmem_cache *s, enum stat_item si)
 {
 #ifdef CONFIG_SLUB_STATS
@@ -4546,6 +4553,9 @@  int __kmem_cache_create(struct kmem_cache *s, slab_flags_t flags)
 	if (err)
 		__kmem_cache_release(s);
 
+	if (s->flags & SLAB_STORE_USER)
+		debugfs_slab_add(s);
+
 	return err;
 }
 
@@ -4686,6 +4696,8 @@  static long validate_slab_cache(struct kmem_cache *s)
 
 	return count;
 }
+
+#ifdef CONFIG_DEBUG_FS
 /*
  * Generate lists of code addresses where slabcache objects are allocated
  * and freed.
@@ -4709,6 +4721,8 @@  struct loc_track {
 	struct location *loc;
 };
 
+static struct dentry *slab_debugfs_root;
+
 static void free_loc_track(struct loc_track *t)
 {
 	if (t->max)
@@ -4825,82 +4839,7 @@  static void process_slab(struct loc_track *t, struct kmem_cache *s,
 			add_location(t, s, get_track(s, p, alloc));
 	put_map(map);
 }
-
-static int list_locations(struct kmem_cache *s, char *buf,
-			  enum track_item alloc)
-{
-	int len = 0;
-	unsigned long i;
-	struct loc_track t = { 0, 0, NULL };
-	int node;
-	struct kmem_cache_node *n;
-
-	if (!alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location),
-			     GFP_KERNEL)) {
-		return sysfs_emit(buf, "Out of memory\n");
-	}
-	/* Push back cpu slabs */
-	flush_all(s);
-
-	for_each_kmem_cache_node(s, node, n) {
-		unsigned long flags;
-		struct page *page;
-
-		if (!atomic_long_read(&n->nr_slabs))
-			continue;
-
-		spin_lock_irqsave(&n->list_lock, flags);
-		list_for_each_entry(page, &n->partial, slab_list)
-			process_slab(&t, s, page, alloc);
-		list_for_each_entry(page, &n->full, slab_list)
-			process_slab(&t, s, page, alloc);
-		spin_unlock_irqrestore(&n->list_lock, flags);
-	}
-
-	for (i = 0; i < t.count; i++) {
-		struct location *l = &t.loc[i];
-
-		len += sysfs_emit_at(buf, len, "%7ld ", l->count);
-
-		if (l->addr)
-			len += sysfs_emit_at(buf, len, "%pS", (void *)l->addr);
-		else
-			len += sysfs_emit_at(buf, len, "<not-available>");
-
-		if (l->sum_time != l->min_time)
-			len += sysfs_emit_at(buf, len, " age=%ld/%ld/%ld",
-					     l->min_time,
-					     (long)div_u64(l->sum_time,
-							   l->count),
-					     l->max_time);
-		else
-			len += sysfs_emit_at(buf, len, " age=%ld", l->min_time);
-
-		if (l->min_pid != l->max_pid)
-			len += sysfs_emit_at(buf, len, " pid=%ld-%ld",
-					     l->min_pid, l->max_pid);
-		else
-			len += sysfs_emit_at(buf, len, " pid=%ld",
-					     l->min_pid);
-
-		if (num_online_cpus() > 1 &&
-		    !cpumask_empty(to_cpumask(l->cpus)))
-			len += sysfs_emit_at(buf, len, " cpus=%*pbl",
-					     cpumask_pr_args(to_cpumask(l->cpus)));
-
-		if (nr_online_nodes > 1 && !nodes_empty(l->nodes))
-			len += sysfs_emit_at(buf, len, " nodes=%*pbl",
-					     nodemask_pr_args(&l->nodes));
-
-		len += sysfs_emit_at(buf, len, "\n");
-	}
-
-	free_loc_track(&t);
-	if (!t.count)
-		len += sysfs_emit_at(buf, len, "No data\n");
-
-	return len;
-}
+#endif  /* CONFIG_DEBUG_FS   */
 #endif	/* CONFIG_SLUB_DEBUG */
 
 #ifdef SLUB_RESILIENCY_TEST
@@ -5350,21 +5289,6 @@  static ssize_t validate_store(struct kmem_cache *s,
 }
 SLAB_ATTR(validate);
 
-static ssize_t alloc_calls_show(struct kmem_cache *s, char *buf)
-{
-	if (!(s->flags & SLAB_STORE_USER))
-		return -ENOSYS;
-	return list_locations(s, buf, TRACK_ALLOC);
-}
-SLAB_ATTR_RO(alloc_calls);
-
-static ssize_t free_calls_show(struct kmem_cache *s, char *buf)
-{
-	if (!(s->flags & SLAB_STORE_USER))
-		return -ENOSYS;
-	return list_locations(s, buf, TRACK_FREE);
-}
-SLAB_ATTR_RO(free_calls);
 #endif /* CONFIG_SLUB_DEBUG */
 
 #ifdef CONFIG_FAILSLAB
@@ -5528,8 +5452,6 @@  static struct attribute *slab_attrs[] = {
 	&poison_attr.attr,
 	&store_user_attr.attr,
 	&validate_attr.attr,
-	&alloc_calls_attr.attr,
-	&free_calls_attr.attr,
 #endif
 #ifdef CONFIG_ZONE_DMA
 	&cache_dma_attr.attr,
@@ -5818,6 +5740,181 @@  static int __init slab_sysfs_init(void)
 __initcall(slab_sysfs_init);
 #endif /* CONFIG_SYSFS */
 
+#if defined(CONFIG_SLUB_DEBUG) && defined(CONFIG_DEBUG_FS)
+static int slab_debugfs_show(struct seq_file *seq, void *v)
+{
+
+	struct location *l;
+	unsigned int idx = *(unsigned int *)v;
+	struct loc_track *t = seq->private;
+
+	if (idx < t->count) {
+		l = &t->loc[idx];
+
+		seq_printf(seq, "%7ld ", l->count);
+
+		if (l->addr)
+			seq_printf(seq, "%pS", (void *)l->addr);
+		else
+			seq_puts(seq, "<not-available>");
+
+		if (l->sum_time != l->min_time) {
+			seq_printf(seq, " age=%ld/%llu/%ld",
+				l->min_time, div_u64(l->sum_time, l->count),
+				l->max_time);
+		} else
+			seq_printf(seq, " age=%ld", l->min_time);
+
+		if (l->min_pid != l->max_pid)
+			seq_printf(seq, " pid=%ld-%ld", l->min_pid, l->max_pid);
+		else
+			seq_printf(seq, " pid=%ld",
+				l->min_pid);
+
+		if (num_online_cpus() > 1 && !cpumask_empty(to_cpumask(l->cpus)))
+			seq_printf(seq, " cpus=%*pbl",
+				 cpumask_pr_args(to_cpumask(l->cpus)));
+
+		if (nr_online_nodes > 1 && !nodes_empty(l->nodes))
+			seq_printf(seq, " nodes=%*pbl",
+				 nodemask_pr_args(&l->nodes));
+
+		seq_puts(seq, "\n");
+	}
+
+	if (!idx && !t->count)
+		seq_puts(seq, "No data\n");
+
+	return 0;
+}
+
+static void slab_debugfs_stop(struct seq_file *seq, void *v)
+{
+	kfree(v);
+}
+
+static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos)
+{
+	loff_t *spos = v;
+	struct loc_track *t = seq->private;
+
+	if (*ppos < t->count) {
+		*ppos = ++*spos;
+		return spos;
+	}
+	*ppos = ++*spos;
+	return NULL;
+}
+
+static void *slab_debugfs_start(struct seq_file *seq, loff_t *ppos)
+{
+	loff_t *spos = kmalloc(sizeof(loff_t), GFP_KERNEL);
+
+	if (!spos)
+		return NULL;
+
+	*spos = *ppos;
+	return spos;
+}
+
+static const struct seq_operations slab_debugfs_sops = {
+	.start  = slab_debugfs_start,
+	.next   = slab_debugfs_next,
+	.stop   = slab_debugfs_stop,
+	.show   = slab_debugfs_show,
+};
+
+static int slab_debug_trace_open(struct inode *inode, struct file *filep)
+{
+
+	struct kmem_cache_node *n;
+	enum track_item alloc;
+	int node;
+	struct loc_track *t = __seq_open_private(filep, &slab_debugfs_sops,
+						sizeof(struct loc_track));
+	struct kmem_cache *s = file_inode(filep)->i_private;
+
+	if (strcmp(filep->f_path.dentry->d_name.name, "alloc_traces") == 0)
+		alloc = TRACK_ALLOC;
+	else
+		alloc = TRACK_FREE;
+
+	if (!alloc_loc_track(t, PAGE_SIZE / sizeof(struct location), GFP_KERNEL))
+		return -ENOMEM;
+
+	/* Push back cpu slabs */
+	flush_all(s);
+
+	for_each_kmem_cache_node(s, node, n) {
+		unsigned long flags;
+		struct page *page;
+
+		if (!atomic_long_read(&n->nr_slabs))
+			continue;
+
+		spin_lock_irqsave(&n->list_lock, flags);
+		list_for_each_entry(page, &n->partial, slab_list)
+			process_slab(t, s, page, alloc);
+		list_for_each_entry(page, &n->full, slab_list)
+			process_slab(t, s, page, alloc);
+		spin_unlock_irqrestore(&n->list_lock, flags);
+	}
+
+	return 0;
+}
+
+static int slab_debug_trace_release(struct inode *inode, struct file *file)
+{
+	struct seq_file *seq = file->private_data;
+	struct loc_track *t = seq->private;
+
+	free_loc_track(t);
+	return seq_release_private(inode, file);
+}
+
+static const struct file_operations slab_debugfs_fops = {
+	.open    = slab_debug_trace_open,
+	.read    = seq_read,
+	.llseek  = seq_lseek,
+	.release = slab_debug_trace_release,
+};
+
+static void debugfs_slab_add(struct kmem_cache *s)
+{
+	struct dentry *slab_cache_dir;
+
+	if (unlikely(!slab_debugfs_root))
+		return;
+
+	slab_cache_dir = debugfs_create_dir(s->name, slab_debugfs_root);
+
+	debugfs_create_file("alloc_traces", 0400,
+		slab_cache_dir, s, &slab_debugfs_fops);
+
+	debugfs_create_file("free_traces", 0400,
+		slab_cache_dir, s, &slab_debugfs_fops);
+}
+
+void debugfs_slab_release(struct kmem_cache *s)
+{
+	debugfs_remove_recursive(debugfs_lookup(s->name, slab_debugfs_root));
+}
+
+static int __init slab_debugfs_init(void)
+{
+	struct kmem_cache *s;
+
+	slab_debugfs_root = debugfs_create_dir("slab", NULL);
+
+	list_for_each_entry(s, &slab_caches, list)
+		if (s->flags & SLAB_STORE_USER)
+			debugfs_slab_add(s);
+
+	return 0;
+
+}
+__initcall(slab_debugfs_init);
+#endif
 /*
  * The /proc/slabinfo ABI
  */