Re: [PATCH v4 sl-b 0/6] Export return addresses etc. for better diagnostics

["Paul E. McKenney" <paulmck@kernel.org>]

On Fri, Jan 08, 2021 at 04:35:57PM +0100, Vlastimil Babka wrote:
> On 1/8/21 1:26 AM, Paul E. McKenney wrote:
> > On Wed, Jan 06, 2021 at 03:42:12PM -0800, Paul E. McKenney wrote:
> >> On Wed, Jan 06, 2021 at 01:48:43PM -0800, Andrew Morton wrote:
> >> > On Tue, 5 Jan 2021 17:16:03 -0800 "Paul E. McKenney" <paulmck@kernel.org> wrote:
> >> > 
> >> > > This is v4 of the series the improves diagnostics by providing access
> >> > > to additional information including the return addresses, slab names,
> >> > > offsets, and sizes collected by the sl*b allocators and by vmalloc().
> >> > 
> >> > Looks reasonable.  And not as bloaty as I feared, but it does add ~300
> >> > bytes to my allnoconfig build.  Is the CONFIG_ coverage as tight as it
> >> > could be?
> >> 
> >> Glad I managed to exceed your expectations.  ;-)
> >> 
> >> Let's see...  When I do an allnoconfig build, it has CONFIG_PRINTK=n.
> >> Given that this facility is based on printk(), I could create an
> >> additional patch that #ifdef'ed everything out in CONFIG_PRINTK=n kernels.
> >> This would uglify things a bit, but it would save ~300 bytes.
> >> 
> >> If I don't hear otherwise from you, I will put something together,
> >> test it, and send it along.
> > 
> > And is a first draft, very lightly tested.  Thoughts?
> 
> Looks ok, but I'm not sure it's worth the trouble, there's probably tons of
> other code that could be treated like this and nobody is doing that
> systematically (at least I haven't heard about kernel tinyfication effort for
> years)... Up to Andrew I guess.

I am good either way.  ;-)

							Thanx, Paul

> Thanks,
> Vlastimil
> 
> > 							Thanx, Paul
> > 
> > ------------------------------------------------------------------------
> > 
> > commit 4164efdca255093a423b55f44bd788b46d9c648f
> > Author: Paul E. McKenney <paulmck@kernel.org>
> > Date:   Thu Jan 7 13:46:11 2021 -0800
> > 
> >     mm: Don't build mm_dump_obj() on CONFIG_PRINTK=n kernels
> >     
> >     The mem_dump_obj() functionality adds a few hundred bytes, which is a
> >     small price to pay.  Except on kernels built with CONFIG_PRINTK=n, in
> >     which mem_dump_obj() messages will be suppressed.  This commit therefore
> >     makes mem_dump_obj() be a static inline empty function on kernels built
> >     with CONFIG_PRINTK=n and excludes all of its support functions as well.
> >     This avoids kernel bloat on systems that cannot use mem_dump_obj().
> >     
> >     Cc: Christoph Lameter <cl@linux.com>
> >     Cc: Pekka Enberg <penberg@kernel.org>
> >     Cc: David Rientjes <rientjes@google.com>
> >     Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> >     Cc: <linux-mm@kvack.org>
> >     Suggested-by: Andrew Morton <akpm@linux-foundation.org>
> >     Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> > 
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index af7d050..ed75a3a 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -3169,7 +3169,11 @@ unsigned long wp_shared_mapping_range(struct address_space *mapping,
> >  
> >  extern int sysctl_nr_trim_pages;
> >  
> > +#ifdef CONFIG_PRINTK
> >  void mem_dump_obj(void *object);
> > +#else
> > +static inline void mem_dump_obj(void *object) {}
> > +#endif
> >  
> >  #endif /* __KERNEL__ */
> >  #endif /* _LINUX_MM_H */
> > diff --git a/include/linux/slab.h b/include/linux/slab.h
> > index 7ae6040..0c97d78 100644
> > --- a/include/linux/slab.h
> > +++ b/include/linux/slab.h
> > @@ -186,8 +186,10 @@ void kfree(const void *);
> >  void kfree_sensitive(const void *);
> >  size_t __ksize(const void *);
> >  size_t ksize(const void *);
> > +#ifdef CONFIG_PRINTK
> >  bool kmem_valid_obj(void *object);
> >  void kmem_dump_obj(void *object);
> > +#endif
> >  
> >  #ifdef CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR
> >  void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
> > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> > index c18f475..3c8a765 100644
> > --- a/include/linux/vmalloc.h
> > +++ b/include/linux/vmalloc.h
> > @@ -246,7 +246,7 @@ pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
> >  int register_vmap_purge_notifier(struct notifier_block *nb);
> >  int unregister_vmap_purge_notifier(struct notifier_block *nb);
> >  
> > -#ifdef CONFIG_MMU
> > +#if defined(CONFIG_MMU) && defined(CONFIG_PRINTK)
> >  bool vmalloc_dump_obj(void *object);
> >  #else
> >  static inline bool vmalloc_dump_obj(void *object) { return false; }
> > diff --git a/mm/slab.c b/mm/slab.c
> > index dcc55e7..965d277 100644
> > --- a/mm/slab.c
> > +++ b/mm/slab.c
> > @@ -3635,6 +3635,7 @@ void *__kmalloc_node_track_caller(size_t size, gfp_t flags,
> >  EXPORT_SYMBOL(__kmalloc_node_track_caller);
> >  #endif /* CONFIG_NUMA */
> >  
> > +#ifdef CONFIG_PRINTK
> >  void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page)
> >  {
> >  	struct kmem_cache *cachep;
> > @@ -3654,6 +3655,7 @@ void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page)
> >  	if (DEBUG && cachep->flags & SLAB_STORE_USER)
> >  		kpp->kp_ret = *dbg_userword(cachep, objp);
> >  }
> > +#endif
> >  
> >  /**
> >   * __do_kmalloc - allocate memory
> > diff --git a/mm/slab.h b/mm/slab.h
> > index ecad9b5..d2e39ab 100644
> > --- a/mm/slab.h
> > +++ b/mm/slab.h
> > @@ -615,6 +615,7 @@ static inline bool slab_want_init_on_free(struct kmem_cache *c)
> >  	return false;
> >  }
> >  
> > +#ifdef CONFIG_PRINTK
> >  #define KS_ADDRS_COUNT 16
> >  struct kmem_obj_info {
> >  	void *kp_ptr;
> > @@ -626,5 +627,6 @@ struct kmem_obj_info {
> >  	void *kp_stack[KS_ADDRS_COUNT];
> >  };
> >  void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page);
> > +#endif
> >  
> >  #endif /* MM_SLAB_H */
> > diff --git a/mm/slab_common.c b/mm/slab_common.c
> > index b594413..20b2cc6 100644
> > --- a/mm/slab_common.c
> > +++ b/mm/slab_common.c
> > @@ -537,6 +537,7 @@ bool slab_is_available(void)
> >  	return slab_state >= UP;
> >  }
> >  
> > +#ifdef CONFIG_PRINTK
> >  /**
> >   * kmem_valid_obj - does the pointer reference a valid slab object?
> >   * @object: pointer to query.
> > @@ -610,6 +611,7 @@ void kmem_dump_obj(void *object)
> >  		pr_info("    %pS\n", kp.kp_stack[i]);
> >  	}
> >  }
> > +#endif
> >  
> >  #ifndef CONFIG_SLOB
> >  /* Create a cache during boot when no slab services are available yet */
> > diff --git a/mm/slob.c b/mm/slob.c
> > index ef87ada..8726931 100644
> > --- a/mm/slob.c
> > +++ b/mm/slob.c
> > @@ -461,11 +461,13 @@ static void slob_free(void *block, int size)
> >  	spin_unlock_irqrestore(&slob_lock, flags);
> >  }
> >  
> > +#ifdef CONFIG_PRINTK
> >  void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page)
> >  {
> >  	kpp->kp_ptr = object;
> >  	kpp->kp_page = page;
> >  }
> > +#endif
> >  
> >  /*
> >   * End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend.
> > diff --git a/mm/slub.c b/mm/slub.c
> > index 3c1a843..9e205e4 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -3919,6 +3919,7 @@ int __kmem_cache_shutdown(struct kmem_cache *s)
> >  	return 0;
> >  }
> >  
> > +#ifdef CONFIG_PRINTK
> >  void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page)
> >  {
> >  	void *base;
> > @@ -3958,6 +3959,7 @@ void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page)
> >  #endif
> >  #endif
> >  }
> > +#endif
> >  
> >  /********************************************************************
> >   *		Kmalloc subsystem
> > diff --git a/mm/util.c b/mm/util.c
> > index 5487022..2d497fe 100644
> > --- a/mm/util.c
> > +++ b/mm/util.c
> > @@ -983,6 +983,7 @@ int __weak memcmp_pages(struct page *page1, struct page *page2)
> >  	return ret;
> >  }
> >  
> > +#ifdef CONFIG_PRINTK
> >  /**
> >   * mem_dump_obj - Print available provenance information
> >   * @object: object for which to find provenance information.
> > @@ -1013,3 +1014,4 @@ void mem_dump_obj(void *object)
> >  	}
> >  	pr_cont(" non-slab/vmalloc memory.\n");
> >  }
> > +#endif
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index e3229ff..5002fd6 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -3448,6 +3448,7 @@ void pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
> >  }
> >  #endif	/* CONFIG_SMP */
> >  
> > +#ifdef CONFIG_PRINTK
> >  bool vmalloc_dump_obj(void *object)
> >  {
> >  	struct vm_struct *vm;
> > @@ -3460,6 +3461,7 @@ bool vmalloc_dump_obj(void *object)
> >  		vm->nr_pages, (unsigned long)vm->addr, vm->caller);
> >  	return true;
> >  }
> > +#endif
> >  
> >  #ifdef CONFIG_PROC_FS
> >  static void *s_start(struct seq_file *m, loff_t *pos)
> > 
>