diff mbox series

[v4] mm: slub: move sysfs slab alloc/free interfaces to debugfs

Message ID 1618583239-18124-1-git-send-email-faiyazm@codeaurora.org (mailing list archive)
State New
Headers show
Series [v4] mm: slub: move sysfs slab alloc/free interfaces to debugfs | expand

Commit Message

Faiyaz Mohammed April 16, 2021, 2:27 p.m. UTC
alloc_calls and free_calls implementation in sysfs have two issues,
one is PAGE_SIZE limitiation 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 implemeation
to debugfs.

Signed-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>
---
 include/linux/slub_def.h |  10 +++
 mm/slab_common.c         |   9 +++
 mm/slub.c                | 202 ++++++++++++++++++++++++++++++++++++++++++-----
 3 files changed, 200 insertions(+), 21 deletions(-)

Comments

kernel test robot April 16, 2021, 6:47 p.m. UTC | #1
Hi Faiyaz,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v5.12-rc7]
[cannot apply to hnaz-linux-mm/master next-20210416]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Faiyaz-Mohammed/mm-slub-move-sysfs-slab-alloc-free-interfaces-to-debugfs/20210416-222940
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 7e25f40eab52c57ff6772d27d2aef3640a3237d7
config: alpha-randconfig-s031-20210416 (attached as .config)
compiler: alpha-linux-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # apt-get install sparse
        # sparse version: v0.6.3-280-g2cd6d34e-dirty
        # https://github.com/0day-ci/linux/commit/8adf70f166344443e2f4e689e30c5d20f16b234e
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Faiyaz-Mohammed/mm-slub-move-sysfs-slab-alloc-free-interfaces-to-debugfs/20210416-222940
        git checkout 8adf70f166344443e2f4e689e30c5d20f16b234e
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' W=1 ARCH=alpha 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   mm/slub.c: In function 'debugfs_slab_add':
>> mm/slub.c:5896:14: warning: variable 'name' set but not used [-Wunused-but-set-variable]
    5896 |  const char *name;
         |              ^~~~
   mm/slub.c: At top level:
   mm/slub.c:4628: error: unterminated #ifdef
    4628 | #ifdef CONFIG_SLUB_DEBUG
         | 


vim +/name +5896 mm/slub.c

  5893	
  5894	static void debugfs_slab_add(struct kmem_cache *s)
  5895	{
> 5896		const char *name;
  5897		int unmergeable = slab_unmergeable(s);
  5898	
  5899		if (unlikely(!slab_debugfs_root))
  5900			return;
  5901	
  5902		if (!unmergeable && disable_higher_order_debug &&
  5903				(slub_debug & DEBUG_METADATA_FLAGS))
  5904			unmergeable = 1;
  5905	
  5906		if (unmergeable) {
  5907			/*
  5908			 * Slabcache can never be merged so we can use the name proper.
  5909			 * This is typically the case for debug situations. In that
  5910			 * case we can catch duplicate names easily.
  5911			 */
  5912			debugfs_remove(s->slab_cache_dentry);
  5913			name = s->name;
  5914		} else {
  5915			/*
  5916			 * Create a unique name for the slab as a target
  5917			 * for the symlinks.
  5918			 */
  5919			name = create_unique_id(s);
  5920		}
  5921	
  5922		s->slab_cache_dentry = debugfs_create_dir(s->name, slab_debugfs_root);
  5923		if (!IS_ERR(s->slab_cache_dentry)) {
  5924			debugfs_create_file("alloc_trace", 0400,
  5925				s->slab_cache_dentry, s, &slab_debug_fops);
  5926	
  5927			debugfs_create_file("free_trace", 0400,
  5928				s->slab_cache_dentry, s, &slab_debug_fops);
  5929		}
  5930	
  5931		if (!unmergeable) {
  5932			/* Setup first alias */
  5933			debugfs_slab_alias(s, s->name);
  5934		}
  5935	}
  5936	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
kernel test robot April 16, 2021, 8:10 p.m. UTC | #2
Hi Faiyaz,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v5.12-rc7]
[cannot apply to hnaz-linux-mm/master next-20210416]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Faiyaz-Mohammed/mm-slub-move-sysfs-slab-alloc-free-interfaces-to-debugfs/20210416-222940
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 7e25f40eab52c57ff6772d27d2aef3640a3237d7
config: mips-randconfig-r001-20210416 (attached as .config)
compiler: mips64el-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/8adf70f166344443e2f4e689e30c5d20f16b234e
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Faiyaz-Mohammed/mm-slub-move-sysfs-slab-alloc-free-interfaces-to-debugfs/20210416-222940
        git checkout 8adf70f166344443e2f4e689e30c5d20f16b234e
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross W=1 ARCH=mips 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   mm/slab_common.c: In function 'slab_caches_to_rcu_destroy_workfn':
>> mm/slab_common.c:441:3: error: implicit declaration of function 'debugfs_slab_release' [-Werror=implicit-function-declaration]
     441 |   debugfs_slab_release(s);
         |   ^~~~~~~~~~~~~~~~~~~~
   At top level:
   mm/slab_common.c:1124:30: warning: 'slabinfo_proc_ops' defined but not used [-Wunused-const-variable=]
    1124 | static const struct proc_ops slabinfo_proc_ops = {
         |                              ^~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors


vim +/debugfs_slab_release +441 mm/slab_common.c

   409	
   410	static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work)
   411	{
   412		LIST_HEAD(to_destroy);
   413		struct kmem_cache *s, *s2;
   414	
   415		/*
   416		 * On destruction, SLAB_TYPESAFE_BY_RCU kmem_caches are put on the
   417		 * @slab_caches_to_rcu_destroy list.  The slab pages are freed
   418		 * through RCU and the associated kmem_cache are dereferenced
   419		 * while freeing the pages, so the kmem_caches should be freed only
   420		 * after the pending RCU operations are finished.  As rcu_barrier()
   421		 * is a pretty slow operation, we batch all pending destructions
   422		 * asynchronously.
   423		 */
   424		mutex_lock(&slab_mutex);
   425		list_splice_init(&slab_caches_to_rcu_destroy, &to_destroy);
   426		mutex_unlock(&slab_mutex);
   427	
   428		if (list_empty(&to_destroy))
   429			return;
   430	
   431		rcu_barrier();
   432	
   433		list_for_each_entry_safe(s, s2, &to_destroy, list) {
   434			kfence_shutdown_cache(s);
   435	#ifdef SLAB_SUPPORTS_SYSFS
   436			sysfs_slab_release(s);
   437	#else
   438			slab_kmem_cache_release(s);
   439	#endif
   440	#ifdef CONFIG_DEBUG_FS
 > 441			debugfs_slab_release(s);
   442	#endif
   443		}
   444	}
   445	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
Vlastimil Babka April 19, 2021, 12:12 p.m. UTC | #3
On 4/16/21 4:27 PM, Faiyaz Mohammed wrote:
> alloc_calls and free_calls implementation in sysfs have two issues,
> one is PAGE_SIZE limitiation 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 implemeation
> to debugfs.
> 
> Signed-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>
> ---
>  include/linux/slub_def.h |  10 +++
>  mm/slab_common.c         |   9 +++
>  mm/slub.c                | 202 ++++++++++++++++++++++++++++++++++++++++++-----
>  3 files changed, 200 insertions(+), 21 deletions(-)

The patch doesn't compile, as the bots noticed. Had to add a missing #endif
after list_locations().

> diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
> index dcde82a..f8c268d 100644
> --- a/include/linux/slub_def.h
> +++ b/include/linux/slub_def.h
> @@ -110,6 +110,9 @@ struct kmem_cache {
>  #ifdef CONFIG_SYSFS
>  	struct kobject kobj;	/* For sysfs */
>  #endif
> +#ifdef CONFIG_SLUB_DEBUG
> +	struct dentry *slab_cache_dentry;
> +#endif
>  #ifdef CONFIG_SLAB_FREELIST_HARDENED
>  	unsigned long random;
>  #endif
> @@ -159,6 +162,13 @@ static inline void sysfs_slab_release(struct kmem_cache *s)
>  }
>  #endif
>  
> +#ifdef CONFIG_DEBUG_FS
> +void debugfs_slab_release(struct kmem_cache *);
> +#else
> +static inline void debugfs_slab_release(struct kmem_cache *s)
> +{
> +}
> +#endif
>  void object_err(struct kmem_cache *s, struct page *page,
>  		u8 *object, char *reason);
>  
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 88e8339..fb28328 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -437,6 +437,9 @@ static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work)
>  #else
>  		slab_kmem_cache_release(s);
>  #endif
> +#ifdef CONFIG_DEBUG_FS
> +		debugfs_slab_release(s);
> +#endif
>  	}
>  }
>  
> @@ -454,6 +457,9 @@ static int shutdown_cache(struct kmem_cache *s)
>  #ifdef SLAB_SUPPORTS_SYSFS
>  		sysfs_slab_unlink(s);
>  #endif
> +#ifdef CONFIG_DEBUG_FS
> +		debugfs_slab_release(s);
> +#endif
>  		list_add_tail(&s->list, &slab_caches_to_rcu_destroy);
>  		schedule_work(&slab_caches_to_rcu_destroy_work);
>  	} else {
> @@ -464,6 +470,9 @@ static int shutdown_cache(struct kmem_cache *s)
>  #else
>  		slab_kmem_cache_release(s);
>  #endif
> +#ifdef CONFIG_DEBUG_FS
> +		debugfs_slab_release(s);
> +#endif
>  	}
>  
>  	return 0;
> diff --git a/mm/slub.c b/mm/slub.c
> index 3021ce9..ab7a0d3 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 +226,15 @@ static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p)
>  							{ return 0; }
>  #endif
>  
> +#ifdef CONFIG_DEBUG_FS
> +static void debugfs_slab_add(struct kmem_cache *);
> +static int debugfs_slab_alias(struct kmem_cache *, const char *);
> +#else
> +static inline void debugfs_slab_add(struct kmem_cache *s) { }
> +static inline int debugfs_slab_alias(struct kmem_cache *s, const char *p)
> +							{ return 0; }
> +#endif
> +
>  static inline void stat(const struct kmem_cache *s, enum stat_item si)
>  {
>  #ifdef CONFIG_SLUB_STATS
> @@ -4521,6 +4531,8 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
>  			s->refcount--;
>  			s = NULL;
>  		}
> +
> +		debugfs_slab_alias(s, name);
>  	}
>  
>  	return s;
> @@ -4542,6 +4554,8 @@ int __kmem_cache_create(struct kmem_cache *s, slab_flags_t flags)
>  	if (err)
>  		__kmem_cache_release(s);
>  
> +	debugfs_slab_add(s);
> +
>  	return err;
>  }
>  
> @@ -4682,6 +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.
> @@ -4705,6 +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)
> @@ -4822,10 +4840,9 @@ static void process_slab(struct loc_track *t, struct kmem_cache *s,
>  	put_map(map);
>  }
>  
> -static int list_locations(struct kmem_cache *s, char *buf,
> +static int list_locations(struct seq_file *seq, struct kmem_cache *s,
>  			  enum track_item alloc)
>  {
> -	int len = 0;
>  	unsigned long i;
>  	struct loc_track t = { 0, 0, NULL };
>  	int node;
> @@ -4833,7 +4850,8 @@ static int list_locations(struct kmem_cache *s, char *buf,
>  
>  	if (!alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location),
>  			     GFP_KERNEL)) {
> -		return sysfs_emit(buf, "Out of memory\n");
> +		seq_puts(seq, "Out of memory\n");
> +		return -ENOMEM;
>  	}
>  	/* Push back cpu slabs */
>  	flush_all(s);
> @@ -4856,46 +4874,46 @@ static int list_locations(struct kmem_cache *s, char *buf,
>  	for (i = 0; i < t.count; i++) {
>  		struct location *l = &t.loc[i];
>  
> -		len += sysfs_emit_at(buf, len, "%7ld ", l->count);
> +		seq_printf(seq, "%7ld ", l->count);
>  
>  		if (l->addr)
> -			len += sysfs_emit_at(buf, len, "%pS", (void *)l->addr);
> +			seq_printf(seq, "%pS", (void *)l->addr);
>  		else
> -			len += sysfs_emit_at(buf, len, "<not-available>");
> +			seq_puts(seq, "<not-available>");
>  
>  		if (l->sum_time != l->min_time)
> -			len += sysfs_emit_at(buf, len, " age=%ld/%ld/%ld",
> +			seq_printf(seq, " 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);
> +			seq_printf(seq, " age=%ld", l->min_time);
>  
>  		if (l->min_pid != l->max_pid)
> -			len += sysfs_emit_at(buf, len, " pid=%ld-%ld",
> +			seq_printf(seq, " pid=%ld-%ld",
>  					     l->min_pid, l->max_pid);
>  		else
> -			len += sysfs_emit_at(buf, len, " pid=%ld",
> +			seq_printf(seq, " pid=%ld",
>  					     l->min_pid);
>  
>  		if (num_online_cpus() > 1 &&
>  		    !cpumask_empty(to_cpumask(l->cpus)))
> -			len += sysfs_emit_at(buf, len, " cpus=%*pbl",
> +			seq_printf(seq, " 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",
> +			seq_printf(seq, " nodes=%*pbl",
>  					     nodemask_pr_args(&l->nodes));
>  
> -		len += sysfs_emit_at(buf, len, "\n");
> +		seq_puts(seq, "\n");
>  	}
>  
>  	free_loc_track(&t);
>  	if (!t.count)
> -		len += sysfs_emit_at(buf, len, "No data\n");
> +		seq_puts(seq, "No data\n");
>  
> -	return len;
> +	return 0;
>  }
>  #endif	/* CONFIG_SLUB_DEBUG */
>  
> @@ -5348,17 +5366,23 @@ 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);
> +	int len = 0;
> +
> +	len += sprintf(buf, "Deprecated, use the equvalent under");
> +	len += sprintf(buf, "/sys/kernel/debug/slab/%s/alloc_calls", s->name);

This doesn't work properly, the second printf() overwrites the first one, also
it's not newline-terminated.
Also debugfs does not have to be always mounted as /sys/kernel/debug. But maybe
it's common enough that the suggestion will work most of the time, so we can
probably leave it.

> +	return len;
>  }
>  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);
> +	int len = 0;
> +
> +	len += sprintf(buf, "Deprecated, use the equvalent under");
> +	len += sprintf(buf, "/sys/kernel/debug/slab/%s/free_calls", s->name);
> +
> +	return len;
>  }
>  SLAB_ATTR_RO(free_calls);
>  #endif /* CONFIG_SLUB_DEBUG */
> @@ -5814,6 +5838,142 @@ 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 debugfs_slab_alias(struct kmem_cache *s, const char *name)
> +{
> +	struct saved_alias *al;
> +
> +	if (slab_state == FULL) {
> +		/*
> +		 * If we have a leftover link then remove it.
> +		 */
> +		debugfs_remove(s->slab_cache_dentry);
> +		s->slab_cache_dentry = debugfs_create_symlink(name, slab_debugfs_root, NULL);
> +		return IS_ERR(s->slab_cache_dentry);
> +	}
> +
> +	al = kmalloc(sizeof(struct saved_alias), GFP_KERNEL);
> +	if (!al)
> +		return -ENOMEM;
> +
> +	al->s = s;
> +	al->name = name;
> +	al->next = alias_list;
> +	alias_list = al;
> +	return 0;
> +}
> +
> +static int slab_debug_trace(struct seq_file *seq, void *ignored)
> +{
> +	struct kmem_cache *s = seq->private;
> +
> +	if (!(s->flags & SLAB_STORE_USER))
> +		return 0;
> +
> +	if (strcmp(seq->file->f_path.dentry->d_name.name, "alloc_trace") == 0)
> +		return list_locations(seq, s, TRACK_ALLOC);
> +	else
> +		return list_locations(seq, s, TRACK_FREE);
> +
> +	return 0;
> +}
> +
> +static int slab_debug_trace_open(struct inode *inode, struct file *filp)
> +{
> +	return single_open(filp, slab_debug_trace,
> +				file_inode(filp)->i_private);

So using single_open() makes things simple, yeah. But IMHO it's still abusing
the seq_file interface. We do iterate over the loc_track objects so we should
better use the proper iteration approach as described in
Documentation/filesystems/seq_file.rst
and used e.g. in fs/proc/task_mmu.c for /proc/pid/smaps etc.

Right now this relies on the implementation of traverse() which starts by
allocating a PAGE_SIZE buffer and if the output doesn't fit, it keeps
reallocating twice the size and repeating the output, thus the call to
list_location(). That's suboptimal.

Also we should probably mimic the return -ENOSYS approach of the sysfs variant
if tracking is not enabled for the cache.

> +}
> +
> +static const struct file_operations slab_debug_fops = {
> +	.open    = slab_debug_trace_open,
> +	.read    = seq_read,
> +	.llseek  = seq_lseek,
> +	.release = single_release,
> +};
> +
> +static void debugfs_slab_add(struct kmem_cache *s)
> +{
> +	const char *name;
> +	int unmergeable = slab_unmergeable(s);
> +
> +	if (unlikely(!slab_debugfs_root))
> +		return;
> +
> +	if (!unmergeable && disable_higher_order_debug &&
> +			(slub_debug & DEBUG_METADATA_FLAGS))
> +		unmergeable = 1;
> +
> +	if (unmergeable) {
> +		/*
> +		 * Slabcache can never be merged so we can use the name proper.
> +		 * This is typically the case for debug situations. In that
> +		 * case we can catch duplicate names easily.
> +		 */
> +		debugfs_remove(s->slab_cache_dentry);
> +		name = s->name;
> +	} else {
> +		/*
> +		 * Create a unique name for the slab as a target
> +		 * for the symlinks.
> +		 */
> +		name = create_unique_id(s);

You don't seem to be actually using the unique name?
When testing your patch, I don't see the hierarchy of /sys/kernel/slab mirrored
in /sys/kernel/debug/slab. There are no directories with the unique names and
symlinks from normal names, it seems all the caches that are aliases are just
missing completely from /sys/kernel/debug/slab

> +	}
> +
> +	s->slab_cache_dentry = debugfs_create_dir(s->name, slab_debugfs_root);
> +	if (!IS_ERR(s->slab_cache_dentry)) {
> +		debugfs_create_file("alloc_trace", 0400,
> +			s->slab_cache_dentry, s, &slab_debug_fops);
> +
> +		debugfs_create_file("free_trace", 0400,
> +			s->slab_cache_dentry, s, &slab_debug_fops);

Was it intentional to rename alloc_calls and free_calls to alloc_trace and
free_trace? You should say in the changelog why.
I would agree with the new names as Oliver is in fact working on a patch to add
actual stack traces to the file instead of just immediate callers. And your
patch to move these files to debugfs to allow longer output is a required
prerequisity for that. But IMHO it would be more correct to call the files
"alloc_traces" and "free_traces".

> +	}
> +
> +	if (!unmergeable) {
> +		/* Setup first alias */
> +		debugfs_slab_alias(s, s->name);
> +	}
> +}
> +
> +void debugfs_slab_release(struct kmem_cache *s)
> +{
> +	if (slab_state >= FULL)
> +		debugfs_remove_recursive(s->slab_cache_dentry);
> +}
> +
> +static int __init slab_debugfs_init(void)
> +{
> +	struct kmem_cache *s;
> +	int err;
> +
> +	slab_debugfs_root = debugfs_create_dir("slab", NULL);
> +	if (!IS_ERR(slab_debugfs_root)) {
> +
> +		slab_state = FULL;
> +
> +		list_for_each_entry(s, &slab_caches, list)
> +			debugfs_slab_add(s);
> +	} else {
> +		pr_err("Cannot create slab debugfs.\n");
> +		return IS_ERR(slab_debugfs_root);
> +	}
> +
> +	while (alias_list) {
> +		struct saved_alias *al = alias_list;
> +
> +		alias_list = alias_list->next;
> +
> +		err = debugfs_slab_alias(al->s, al->name);
> +		if (err)
> +			pr_err("SLUB: Unable to add boot slab alias %s to debugfs\n",
> +			       al->name);
> +		kfree(al);
> +	}
> +
> +	return 0;
> +
> +}
> +__initcall(slab_debugfs_init);
> +#endif
>  /*
>   * The /proc/slabinfo ABI
>   */
>
Faiyaz Mohammed May 6, 2021, 10:16 a.m. UTC | #4
On 4/19/2021 5:42 PM, Vlastimil Babka wrote:
> On 4/16/21 4:27 PM, Faiyaz Mohammed wrote:
>> alloc_calls and free_calls implementation in sysfs have two issues,
>> one is PAGE_SIZE limitiation 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 implemeation
>> to debugfs.
>>
>> Signed-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>
>> ---
>>  include/linux/slub_def.h |  10 +++
>>  mm/slab_common.c         |   9 +++
>>  mm/slub.c                | 202 ++++++++++++++++++++++++++++++++++++++++++-----
>>  3 files changed, 200 insertions(+), 21 deletions(-)
> 
> The patch doesn't compile, as the bots noticed. Had to add a missing #endif
> after list_locations().
> 
My bad, I think I miss. Updated the patch.

>> diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
>> index dcde82a..f8c268d 100644
>> --- a/include/linux/slub_def.h
>> +++ b/include/linux/slub_def.h
>> @@ -110,6 +110,9 @@ struct kmem_cache {
>>  #ifdef CONFIG_SYSFS
>>  	struct kobject kobj;	/* For sysfs */
>>  #endif
>> +#ifdef CONFIG_SLUB_DEBUG
>> +	struct dentry *slab_cache_dentry;
>> +#endif
>>  #ifdef CONFIG_SLAB_FREELIST_HARDENED
>>  	unsigned long random;
>>  #endif
>> @@ -159,6 +162,13 @@ static inline void sysfs_slab_release(struct kmem_cache *s)
>>  }
>>  #endif
>>  
>> +#ifdef CONFIG_DEBUG_FS
>> +void debugfs_slab_release(struct kmem_cache *);
>> +#else
>> +static inline void debugfs_slab_release(struct kmem_cache *s)
>> +{
>> +}
>> +#endif
>>  void object_err(struct kmem_cache *s, struct page *page,
>>  		u8 *object, char *reason);
>>  
>> diff --git a/mm/slab_common.c b/mm/slab_common.c
>> index 88e8339..fb28328 100644
>> --- a/mm/slab_common.c
>> +++ b/mm/slab_common.c
>> @@ -437,6 +437,9 @@ static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work)
>>  #else
>>  		slab_kmem_cache_release(s);
>>  #endif
>> +#ifdef CONFIG_DEBUG_FS
>> +		debugfs_slab_release(s);
>> +#endif
>>  	}
>>  }
>>  
>> @@ -454,6 +457,9 @@ static int shutdown_cache(struct kmem_cache *s)
>>  #ifdef SLAB_SUPPORTS_SYSFS
>>  		sysfs_slab_unlink(s);
>>  #endif
>> +#ifdef CONFIG_DEBUG_FS
>> +		debugfs_slab_release(s);
>> +#endif
>>  		list_add_tail(&s->list, &slab_caches_to_rcu_destroy);
>>  		schedule_work(&slab_caches_to_rcu_destroy_work);
>>  	} else {
>> @@ -464,6 +470,9 @@ static int shutdown_cache(struct kmem_cache *s)
>>  #else
>>  		slab_kmem_cache_release(s);
>>  #endif
>> +#ifdef CONFIG_DEBUG_FS
>> +		debugfs_slab_release(s);
>> +#endif
>>  	}
>>  
>>  	return 0;
>> diff --git a/mm/slub.c b/mm/slub.c
>> index 3021ce9..ab7a0d3 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 +226,15 @@ static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p)
>>  							{ return 0; }
>>  #endif
>>  
>> +#ifdef CONFIG_DEBUG_FS
>> +static void debugfs_slab_add(struct kmem_cache *);
>> +static int debugfs_slab_alias(struct kmem_cache *, const char *);
>> +#else
>> +static inline void debugfs_slab_add(struct kmem_cache *s) { }
>> +static inline int debugfs_slab_alias(struct kmem_cache *s, const char *p)
>> +							{ return 0; }
>> +#endif
>> +
>>  static inline void stat(const struct kmem_cache *s, enum stat_item si)
>>  {
>>  #ifdef CONFIG_SLUB_STATS
>> @@ -4521,6 +4531,8 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
>>  			s->refcount--;
>>  			s = NULL;
>>  		}
>> +
>> +		debugfs_slab_alias(s, name);
>>  	}
>>  
>>  	return s;
>> @@ -4542,6 +4554,8 @@ int __kmem_cache_create(struct kmem_cache *s, slab_flags_t flags)
>>  	if (err)
>>  		__kmem_cache_release(s);
>>  
>> +	debugfs_slab_add(s);
>> +
>>  	return err;
>>  }
>>  
>> @@ -4682,6 +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.
>> @@ -4705,6 +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)
>> @@ -4822,10 +4840,9 @@ static void process_slab(struct loc_track *t, struct kmem_cache *s,
>>  	put_map(map);
>>  }
>>  
>> -static int list_locations(struct kmem_cache *s, char *buf,
>> +static int list_locations(struct seq_file *seq, struct kmem_cache *s,
>>  			  enum track_item alloc)
>>  {
>> -	int len = 0;
>>  	unsigned long i;
>>  	struct loc_track t = { 0, 0, NULL };
>>  	int node;
>> @@ -4833,7 +4850,8 @@ static int list_locations(struct kmem_cache *s, char *buf,
>>  
>>  	if (!alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location),
>>  			     GFP_KERNEL)) {
>> -		return sysfs_emit(buf, "Out of memory\n");
>> +		seq_puts(seq, "Out of memory\n");
>> +		return -ENOMEM;
>>  	}
>>  	/* Push back cpu slabs */
>>  	flush_all(s);
>> @@ -4856,46 +4874,46 @@ static int list_locations(struct kmem_cache *s, char *buf,
>>  	for (i = 0; i < t.count; i++) {
>>  		struct location *l = &t.loc[i];
>>  
>> -		len += sysfs_emit_at(buf, len, "%7ld ", l->count);
>> +		seq_printf(seq, "%7ld ", l->count);
>>  
>>  		if (l->addr)
>> -			len += sysfs_emit_at(buf, len, "%pS", (void *)l->addr);
>> +			seq_printf(seq, "%pS", (void *)l->addr);
>>  		else
>> -			len += sysfs_emit_at(buf, len, "<not-available>");
>> +			seq_puts(seq, "<not-available>");
>>  
>>  		if (l->sum_time != l->min_time)
>> -			len += sysfs_emit_at(buf, len, " age=%ld/%ld/%ld",
>> +			seq_printf(seq, " 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);
>> +			seq_printf(seq, " age=%ld", l->min_time);
>>  
>>  		if (l->min_pid != l->max_pid)
>> -			len += sysfs_emit_at(buf, len, " pid=%ld-%ld",
>> +			seq_printf(seq, " pid=%ld-%ld",
>>  					     l->min_pid, l->max_pid);
>>  		else
>> -			len += sysfs_emit_at(buf, len, " pid=%ld",
>> +			seq_printf(seq, " pid=%ld",
>>  					     l->min_pid);
>>  
>>  		if (num_online_cpus() > 1 &&
>>  		    !cpumask_empty(to_cpumask(l->cpus)))
>> -			len += sysfs_emit_at(buf, len, " cpus=%*pbl",
>> +			seq_printf(seq, " 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",
>> +			seq_printf(seq, " nodes=%*pbl",
>>  					     nodemask_pr_args(&l->nodes));
>>  
>> -		len += sysfs_emit_at(buf, len, "\n");
>> +		seq_puts(seq, "\n");
>>  	}
>>  
>>  	free_loc_track(&t);
>>  	if (!t.count)
>> -		len += sysfs_emit_at(buf, len, "No data\n");
>> +		seq_puts(seq, "No data\n");
>>  
>> -	return len;
>> +	return 0;
>>  }
>>  #endif	/* CONFIG_SLUB_DEBUG */
>>  
>> @@ -5348,17 +5366,23 @@ 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);
>> +	int len = 0;
>> +
>> +	len += sprintf(buf, "Deprecated, use the equvalent under");
>> +	len += sprintf(buf, "/sys/kernel/debug/slab/%s/alloc_calls", s->name);
> 
> This doesn't work properly, the second printf() overwrites the first one, also
> it's not newline-terminated.
> Also debugfs does not have to be always mounted as /sys/kernel/debug. But maybe
> it's common enough that the suggestion will work most of the time, so we can
> probably leave it.
>
added new line. Updated the patch.

>> +	return len;
>>  }
>>  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);
>> +	int len = 0;
>> +
>> +	len += sprintf(buf, "Deprecated, use the equvalent under");
>> +	len += sprintf(buf, "/sys/kernel/debug/slab/%s/free_calls", s->name);
>> +
>> +	return len;
>>  }
>>  SLAB_ATTR_RO(free_calls);
>>  #endif /* CONFIG_SLUB_DEBUG */
>> @@ -5814,6 +5838,142 @@ 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 debugfs_slab_alias(struct kmem_cache *s, const char *name)
>> +{
>> +	struct saved_alias *al;
>> +
>> +	if (slab_state == FULL) {
>> +		/*
>> +		 * If we have a leftover link then remove it.
>> +		 */
>> +		debugfs_remove(s->slab_cache_dentry);
>> +		s->slab_cache_dentry = debugfs_create_symlink(name, slab_debugfs_root, NULL);
>> +		return IS_ERR(s->slab_cache_dentry);
>> +	}
>> +
>> +	al = kmalloc(sizeof(struct saved_alias), GFP_KERNEL);
>> +	if (!al)
>> +		return -ENOMEM;
>> +
>> +	al->s = s;
>> +	al->name = name;
>> +	al->next = alias_list;
>> +	alias_list = al;
>> +	return 0;
>> +}
>> +
>> +static int slab_debug_trace(struct seq_file *seq, void *ignored)
>> +{
>> +	struct kmem_cache *s = seq->private;
>> +
>> +	if (!(s->flags & SLAB_STORE_USER))
>> +		return 0;
>> +
>> +	if (strcmp(seq->file->f_path.dentry->d_name.name, "alloc_trace") == 0)
>> +		return list_locations(seq, s, TRACK_ALLOC);
>> +	else
>> +		return list_locations(seq, s, TRACK_FREE);
>> +
>> +	return 0;
>> +}
>> +
>> +static int slab_debug_trace_open(struct inode *inode, struct file *filp)
>> +{
>> +	return single_open(filp, slab_debug_trace,
>> +				file_inode(filp)->i_private);
> 
> So using single_open() makes things simple, yeah. But IMHO it's still abusing
> the seq_file interface. We do iterate over the loc_track objects so we should
> better use the proper iteration approach as described in
> Documentation/filesystems/seq_file.rst
> and used e.g. in fs/proc/task_mmu.c for /proc/pid/smaps etc.
> 
> Right now this relies on the implementation of traverse() which starts by
> allocating a PAGE_SIZE buffer and if the output doesn't fit, it keeps
> reallocating twice the size and repeating the output, thus the call to
> list_location(). That's suboptimal.
> 
> Also we should probably mimic the return -ENOSYS approach of the sysfs variant
> if tracking is not enabled for the cache.
> 
Updated the interface with seq_file ops.

>> +}
>> +
>> +static const struct file_operations slab_debug_fops = {
>> +	.open    = slab_debug_trace_open,
>> +	.read    = seq_read,
>> +	.llseek  = seq_lseek,
>> +	.release = single_release,
>> +};
>> +
>> +static void debugfs_slab_add(struct kmem_cache *s)
>> +{
>> +	const char *name;
>> +	int unmergeable = slab_unmergeable(s);
>> +
>> +	if (unlikely(!slab_debugfs_root))
>> +		return;
>> +
>> +	if (!unmergeable && disable_higher_order_debug &&
>> +			(slub_debug & DEBUG_METADATA_FLAGS))
>> +		unmergeable = 1;
>> +
>> +	if (unmergeable) {
>> +		/*
>> +		 * Slabcache can never be merged so we can use the name proper.
>> +		 * This is typically the case for debug situations. In that
>> +		 * case we can catch duplicate names easily.
>> +		 */
>> +		debugfs_remove(s->slab_cache_dentry);
>> +		name = s->name;
>> +	} else {
>> +		/*
>> +		 * Create a unique name for the slab as a target
>> +		 * for the symlinks.
>> +		 */
>> +		name = create_unique_id(s);
> 
> You don't seem to be actually using the unique name?
> When testing your patch, I don't see the hierarchy of /sys/kernel/slab mirrored
> in /sys/kernel/debug/slab. There are no directories with the unique names and
> symlinks from normal names, it seems all the caches that are aliases are just
> missing completely from /sys/kernel/debug/slabUpdated the new patch.

>> +	}
>> +
>> +	s->slab_cache_dentry = debugfs_create_dir(s->name, slab_debugfs_root);
>> +	if (!IS_ERR(s->slab_cache_dentry)) {
>> +		debugfs_create_file("alloc_trace", 0400,
>> +			s->slab_cache_dentry, s, &slab_debug_fops);
>> +
>> +		debugfs_create_file("free_trace", 0400,
>> +			s->slab_cache_dentry, s, &slab_debug_fops);
> 
> Was it intentional to rename alloc_calls and free_calls to alloc_trace and
> free_trace? You should say in the changelog why.
> I would agree with the new names as Oliver is in fact working on a patch to add
> actual stack traces to the file instead of just immediate callers. And your
> patch to move these files to debugfs to allow longer output is a required
> prerequisity for that. But IMHO it would be more correct to call the files
> "alloc_traces" and "free_traces".
> 
yes, rename the interfaces alloc/free to alloc_traces/free_traces to be
inline with what it does.

>> +	}
>> +
>> +	if (!unmergeable) {
>> +		/* Setup first alias */
>> +		debugfs_slab_alias(s, s->name);
>> +	}
>> +}
>> +
>> +void debugfs_slab_release(struct kmem_cache *s)
>> +{
>> +	if (slab_state >= FULL)
>> +		debugfs_remove_recursive(s->slab_cache_dentry);
>> +}
>> +
>> +static int __init slab_debugfs_init(void)
>> +{
>> +	struct kmem_cache *s;
>> +	int err;
>> +
>> +	slab_debugfs_root = debugfs_create_dir("slab", NULL);
>> +	if (!IS_ERR(slab_debugfs_root)) {
>> +
>> +		slab_state = FULL;
>> +
>> +		list_for_each_entry(s, &slab_caches, list)
>> +			debugfs_slab_add(s);
>> +	} else {
>> +		pr_err("Cannot create slab debugfs.\n");
>> +		return IS_ERR(slab_debugfs_root);
>> +	}
>> +
>> +	while (alias_list) {
>> +		struct saved_alias *al = alias_list;
>> +
>> +		alias_list = alias_list->next;
>> +
>> +		err = debugfs_slab_alias(al->s, al->name);
>> +		if (err)
>> +			pr_err("SLUB: Unable to add boot slab alias %s to debugfs\n",
>> +			       al->name);
>> +		kfree(al);
>> +	}
>> +
>> +	return 0;
>> +
>> +}
>> +__initcall(slab_debugfs_init);
>> +#endif
>>  /*
>>   * The /proc/slabinfo ABI
>>   */
>>
>
diff mbox series

Patch

diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index dcde82a..f8c268d 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -110,6 +110,9 @@  struct kmem_cache {
 #ifdef CONFIG_SYSFS
 	struct kobject kobj;	/* For sysfs */
 #endif
+#ifdef CONFIG_SLUB_DEBUG
+	struct dentry *slab_cache_dentry;
+#endif
 #ifdef CONFIG_SLAB_FREELIST_HARDENED
 	unsigned long random;
 #endif
@@ -159,6 +162,13 @@  static inline void sysfs_slab_release(struct kmem_cache *s)
 }
 #endif
 
+#ifdef CONFIG_DEBUG_FS
+void debugfs_slab_release(struct kmem_cache *);
+#else
+static inline void debugfs_slab_release(struct kmem_cache *s)
+{
+}
+#endif
 void object_err(struct kmem_cache *s, struct page *page,
 		u8 *object, char *reason);
 
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 88e8339..fb28328 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -437,6 +437,9 @@  static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work)
 #else
 		slab_kmem_cache_release(s);
 #endif
+#ifdef CONFIG_DEBUG_FS
+		debugfs_slab_release(s);
+#endif
 	}
 }
 
@@ -454,6 +457,9 @@  static int shutdown_cache(struct kmem_cache *s)
 #ifdef SLAB_SUPPORTS_SYSFS
 		sysfs_slab_unlink(s);
 #endif
+#ifdef CONFIG_DEBUG_FS
+		debugfs_slab_release(s);
+#endif
 		list_add_tail(&s->list, &slab_caches_to_rcu_destroy);
 		schedule_work(&slab_caches_to_rcu_destroy_work);
 	} else {
@@ -464,6 +470,9 @@  static int shutdown_cache(struct kmem_cache *s)
 #else
 		slab_kmem_cache_release(s);
 #endif
+#ifdef CONFIG_DEBUG_FS
+		debugfs_slab_release(s);
+#endif
 	}
 
 	return 0;
diff --git a/mm/slub.c b/mm/slub.c
index 3021ce9..ab7a0d3 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 +226,15 @@  static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p)
 							{ return 0; }
 #endif
 
+#ifdef CONFIG_DEBUG_FS
+static void debugfs_slab_add(struct kmem_cache *);
+static int debugfs_slab_alias(struct kmem_cache *, const char *);
+#else
+static inline void debugfs_slab_add(struct kmem_cache *s) { }
+static inline int debugfs_slab_alias(struct kmem_cache *s, const char *p)
+							{ return 0; }
+#endif
+
 static inline void stat(const struct kmem_cache *s, enum stat_item si)
 {
 #ifdef CONFIG_SLUB_STATS
@@ -4521,6 +4531,8 @@  __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
 			s->refcount--;
 			s = NULL;
 		}
+
+		debugfs_slab_alias(s, name);
 	}
 
 	return s;
@@ -4542,6 +4554,8 @@  int __kmem_cache_create(struct kmem_cache *s, slab_flags_t flags)
 	if (err)
 		__kmem_cache_release(s);
 
+	debugfs_slab_add(s);
+
 	return err;
 }
 
@@ -4682,6 +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.
@@ -4705,6 +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)
@@ -4822,10 +4840,9 @@  static void process_slab(struct loc_track *t, struct kmem_cache *s,
 	put_map(map);
 }
 
-static int list_locations(struct kmem_cache *s, char *buf,
+static int list_locations(struct seq_file *seq, struct kmem_cache *s,
 			  enum track_item alloc)
 {
-	int len = 0;
 	unsigned long i;
 	struct loc_track t = { 0, 0, NULL };
 	int node;
@@ -4833,7 +4850,8 @@  static int list_locations(struct kmem_cache *s, char *buf,
 
 	if (!alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location),
 			     GFP_KERNEL)) {
-		return sysfs_emit(buf, "Out of memory\n");
+		seq_puts(seq, "Out of memory\n");
+		return -ENOMEM;
 	}
 	/* Push back cpu slabs */
 	flush_all(s);
@@ -4856,46 +4874,46 @@  static int list_locations(struct kmem_cache *s, char *buf,
 	for (i = 0; i < t.count; i++) {
 		struct location *l = &t.loc[i];
 
-		len += sysfs_emit_at(buf, len, "%7ld ", l->count);
+		seq_printf(seq, "%7ld ", l->count);
 
 		if (l->addr)
-			len += sysfs_emit_at(buf, len, "%pS", (void *)l->addr);
+			seq_printf(seq, "%pS", (void *)l->addr);
 		else
-			len += sysfs_emit_at(buf, len, "<not-available>");
+			seq_puts(seq, "<not-available>");
 
 		if (l->sum_time != l->min_time)
-			len += sysfs_emit_at(buf, len, " age=%ld/%ld/%ld",
+			seq_printf(seq, " 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);
+			seq_printf(seq, " age=%ld", l->min_time);
 
 		if (l->min_pid != l->max_pid)
-			len += sysfs_emit_at(buf, len, " pid=%ld-%ld",
+			seq_printf(seq, " pid=%ld-%ld",
 					     l->min_pid, l->max_pid);
 		else
-			len += sysfs_emit_at(buf, len, " pid=%ld",
+			seq_printf(seq, " pid=%ld",
 					     l->min_pid);
 
 		if (num_online_cpus() > 1 &&
 		    !cpumask_empty(to_cpumask(l->cpus)))
-			len += sysfs_emit_at(buf, len, " cpus=%*pbl",
+			seq_printf(seq, " 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",
+			seq_printf(seq, " nodes=%*pbl",
 					     nodemask_pr_args(&l->nodes));
 
-		len += sysfs_emit_at(buf, len, "\n");
+		seq_puts(seq, "\n");
 	}
 
 	free_loc_track(&t);
 	if (!t.count)
-		len += sysfs_emit_at(buf, len, "No data\n");
+		seq_puts(seq, "No data\n");
 
-	return len;
+	return 0;
 }
 #endif	/* CONFIG_SLUB_DEBUG */
 
@@ -5348,17 +5366,23 @@  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);
+	int len = 0;
+
+	len += sprintf(buf, "Deprecated, use the equvalent under");
+	len += sprintf(buf, "/sys/kernel/debug/slab/%s/alloc_calls", s->name);
+
+	return len;
 }
 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);
+	int len = 0;
+
+	len += sprintf(buf, "Deprecated, use the equvalent under");
+	len += sprintf(buf, "/sys/kernel/debug/slab/%s/free_calls", s->name);
+
+	return len;
 }
 SLAB_ATTR_RO(free_calls);
 #endif /* CONFIG_SLUB_DEBUG */
@@ -5814,6 +5838,142 @@  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 debugfs_slab_alias(struct kmem_cache *s, const char *name)
+{
+	struct saved_alias *al;
+
+	if (slab_state == FULL) {
+		/*
+		 * If we have a leftover link then remove it.
+		 */
+		debugfs_remove(s->slab_cache_dentry);
+		s->slab_cache_dentry = debugfs_create_symlink(name, slab_debugfs_root, NULL);
+		return IS_ERR(s->slab_cache_dentry);
+	}
+
+	al = kmalloc(sizeof(struct saved_alias), GFP_KERNEL);
+	if (!al)
+		return -ENOMEM;
+
+	al->s = s;
+	al->name = name;
+	al->next = alias_list;
+	alias_list = al;
+	return 0;
+}
+
+static int slab_debug_trace(struct seq_file *seq, void *ignored)
+{
+	struct kmem_cache *s = seq->private;
+
+	if (!(s->flags & SLAB_STORE_USER))
+		return 0;
+
+	if (strcmp(seq->file->f_path.dentry->d_name.name, "alloc_trace") == 0)
+		return list_locations(seq, s, TRACK_ALLOC);
+	else
+		return list_locations(seq, s, TRACK_FREE);
+
+	return 0;
+}
+
+static int slab_debug_trace_open(struct inode *inode, struct file *filp)
+{
+	return single_open(filp, slab_debug_trace,
+				file_inode(filp)->i_private);
+}
+
+static const struct file_operations slab_debug_fops = {
+	.open    = slab_debug_trace_open,
+	.read    = seq_read,
+	.llseek  = seq_lseek,
+	.release = single_release,
+};
+
+static void debugfs_slab_add(struct kmem_cache *s)
+{
+	const char *name;
+	int unmergeable = slab_unmergeable(s);
+
+	if (unlikely(!slab_debugfs_root))
+		return;
+
+	if (!unmergeable && disable_higher_order_debug &&
+			(slub_debug & DEBUG_METADATA_FLAGS))
+		unmergeable = 1;
+
+	if (unmergeable) {
+		/*
+		 * Slabcache can never be merged so we can use the name proper.
+		 * This is typically the case for debug situations. In that
+		 * case we can catch duplicate names easily.
+		 */
+		debugfs_remove(s->slab_cache_dentry);
+		name = s->name;
+	} else {
+		/*
+		 * Create a unique name for the slab as a target
+		 * for the symlinks.
+		 */
+		name = create_unique_id(s);
+	}
+
+	s->slab_cache_dentry = debugfs_create_dir(s->name, slab_debugfs_root);
+	if (!IS_ERR(s->slab_cache_dentry)) {
+		debugfs_create_file("alloc_trace", 0400,
+			s->slab_cache_dentry, s, &slab_debug_fops);
+
+		debugfs_create_file("free_trace", 0400,
+			s->slab_cache_dentry, s, &slab_debug_fops);
+	}
+
+	if (!unmergeable) {
+		/* Setup first alias */
+		debugfs_slab_alias(s, s->name);
+	}
+}
+
+void debugfs_slab_release(struct kmem_cache *s)
+{
+	if (slab_state >= FULL)
+		debugfs_remove_recursive(s->slab_cache_dentry);
+}
+
+static int __init slab_debugfs_init(void)
+{
+	struct kmem_cache *s;
+	int err;
+
+	slab_debugfs_root = debugfs_create_dir("slab", NULL);
+	if (!IS_ERR(slab_debugfs_root)) {
+
+		slab_state = FULL;
+
+		list_for_each_entry(s, &slab_caches, list)
+			debugfs_slab_add(s);
+	} else {
+		pr_err("Cannot create slab debugfs.\n");
+		return IS_ERR(slab_debugfs_root);
+	}
+
+	while (alias_list) {
+		struct saved_alias *al = alias_list;
+
+		alias_list = alias_list->next;
+
+		err = debugfs_slab_alias(al->s, al->name);
+		if (err)
+			pr_err("SLUB: Unable to add boot slab alias %s to debugfs\n",
+			       al->name);
+		kfree(al);
+	}
+
+	return 0;
+
+}
+__initcall(slab_debugfs_init);
+#endif
 /*
  * The /proc/slabinfo ABI
  */