Message-ID: <20210108002657.GA21084@paulmck-ThinkPad-P72>
Date:   Thu, 7 Jan 2021 16:26:57 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, rcu@...r.kernel.org,
        linux-mm@...ck.org, cl@...ux.com, penberg@...nel.org,
        rientjes@...gle.com, iamjoonsoo.kim@....com, ming.lei@...hat.com,
        axboe@...nel.dk, kernel-team@...com
Subject: Re: [PATCH v4 sl-b 0/6] Export return addresses etc. for better
 diagnostics

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@...nel.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?

							Thanx, Paul

------------------------------------------------------------------------

commit 4164efdca255093a423b55f44bd788b46d9c648f
Author: Paul E. McKenney <paulmck@...nel.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@...ux.com>
    Cc: Pekka Enberg <penberg@...nel.org>
    Cc: David Rientjes <rientjes@...gle.com>
    Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
    Cc: <linux-mm@...ck.org>
    Suggested-by: Andrew Morton <akpm@...ux-foundation.org>
    Signed-off-by: Paul E. McKenney <paulmck@...nel.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)

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