slab allocators: Remove SLAB_DEBUG_INITIAL flag

I have never seen a use of SLAB_DEBUG_INITIAL.  It is only supported by
SLAB.

I think its purpose was to have a callback after an object has been freed
to verify that the state is the constructor state again?  The callback is
performed before each freeing of an object.

I would think that it is much easier to check the object state manually
before the free.  That also places the check near the code object
manipulation of the object.

Also the SLAB_DEBUG_INITIAL callback is only performed if the kernel was
compiled with SLAB debugging on.  If there would be code in a constructor
handling SLAB_DEBUG_INITIAL then it would have to be conditional on
SLAB_DEBUG otherwise it would just be dead code.  But there is no such code
in the kernel.  I think SLUB_DEBUG_INITIAL is too problematic to make real
use of, difficult to understand and there are easier ways to accomplish the
same effect (i.e.  add debug code before kfree).

There is a related flag SLAB_CTOR_VERIFY that is frequently checked to be
clear in fs inode caches.  Remove the pointless checks (they would even be
pointless without removeal of SLAB_DEBUG_INITIAL) from the fs constructors.

This is the last slab flag that SLUB did not support.  Remove the check for
unimplemented flags from SLUB.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 4 insertions, 32 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
index 59da5b734c8..75a32be64a2 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -162,8 +162,7 @@ void anon_vma_unlink(struct vm_area_struct *vma)
 static void anon_vma_ctor(void *data, struct kmem_cache *cachep,
 			  unsigned long flags)
 {
-	if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
-						SLAB_CTOR_CONSTRUCTOR) {
+	if (flags & SLAB_CTOR_CONSTRUCTOR) {
 		struct anon_vma *anon_vma = data;
 
 		spin_lock_init(&anon_vma->lock);
diff --git a/mm/shmem.c b/mm/shmem.c
index b2a35ebf071..f01e8deed64 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2358,8 +2358,7 @@ static void init_once(void *foo, struct kmem_cache *cachep,
 {
 	struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
 
-	if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
-	    SLAB_CTOR_CONSTRUCTOR) {
+	if (flags & SLAB_CTOR_CONSTRUCTOR) {
 		inode_init_once(&p->vfs_inode);
 #ifdef CONFIG_TMPFS_POSIX_ACL
 		p->i_acl = NULL;
diff --git a/mm/slab.c b/mm/slab.c
index 2a3cbd6e675..a877d6f3d68 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -116,8 +116,7 @@
 #include	<asm/page.h>
 
 /*
- * DEBUG	- 1 for kmem_cache_create() to honour; SLAB_DEBUG_INITIAL,
- *		  SLAB_RED_ZONE & SLAB_POISON.
+ * DEBUG	- 1 for kmem_cache_create() to honour; SLAB_RED_ZONE & SLAB_POISON.
  *		  0 for faster, smaller code (especially in the critical paths).
  *
  * STATS	- 1 to collect stats for /proc/slabinfo.
@@ -172,7 +171,7 @@
 
 /* Legal flag mask for kmem_cache_create(). */
 #if DEBUG
-# define CREATE_MASK	(SLAB_DEBUG_INITIAL | SLAB_RED_ZONE | \
+# define CREATE_MASK	(SLAB_RED_ZONE | \
 			 SLAB_POISON | SLAB_HWCACHE_ALIGN | \
 			 SLAB_CACHE_DMA | \
 			 SLAB_STORE_USER | \
@@ -2184,12 +2183,6 @@ kmem_cache_create (const char *name, size_t size, size_t align,
 
 #if DEBUG
 	WARN_ON(strchr(name, ' '));	/* It confuses parsers */
-	if ((flags & SLAB_DEBUG_INITIAL) && !ctor) {
-		/* No constructor, but inital state check requested */
-		printk(KERN_ERR "%s: No con, but init state check "
-		       "requested - %s\n", __FUNCTION__, name);
-		flags &= ~SLAB_DEBUG_INITIAL;
-	}
 #if FORCED_DEBUG
 	/*
 	 * Enable redzoning and last user accounting, except for caches with
@@ -2895,15 +2888,6 @@ static void *cache_free_debugcheck(struct kmem_cache *cachep, void *objp,
 	BUG_ON(objnr >= cachep->num);
 	BUG_ON(objp != index_to_obj(cachep, slabp, objnr));
 
-	if (cachep->flags & SLAB_DEBUG_INITIAL) {
-		/*
-		 * Need to call the slab's constructor so the caller can
-		 * perform a verify of its state (debugging).  Called without
-		 * the cache-lock held.
-		 */
-		cachep->ctor(objp + obj_offset(cachep),
-			     cachep, SLAB_CTOR_CONSTRUCTOR | SLAB_CTOR_VERIFY);
-	}
 	if (cachep->flags & SLAB_POISON && cachep->dtor) {
 		/* we want to cache poison the object,
 		 * call the destruction callback
diff --git a/mm/slub.c b/mm/slub.c
index 79940e98e5e..bd86182e595 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -97,9 +97,6 @@
  *
  * - Support PAGE_ALLOC_DEBUG. Should be easy to do.
  *
- * - SLAB_DEBUG_INITIAL is not supported but I have never seen a use of
- *   it.
- *
  * - Variable sizing of the per node arrays
  */
 
@@ -126,11 +123,6 @@
 #endif
 
 /*
- * Flags from the regular SLAB that SLUB does not support:
- */
-#define SLUB_UNIMPLEMENTED (SLAB_DEBUG_INITIAL)
-
-/*
  * Mininum number of partial slabs. These will be left on the partial
  * lists even if they are empty. kmem_cache_shrink may reclaim them.
  */
@@ -1748,8 +1740,6 @@ static int kmem_cache_open(struct kmem_cache *s, gfp_t gfpflags,
 	s->flags = flags;
 	s->align = align;
 
-	BUG_ON(flags & SLUB_UNIMPLEMENTED);
-
 	/*
 	 * The page->offset field is only 16 bit wide. This is an offset
 	 * in units of words from the beginning of an object. If the slab