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>

1 files changed, 0 insertions, 2 deletions

diff --git a/include/linux/slab.h b/include/linux/slab.h
index e14b4c338b8..1ffe0a959cd 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -21,7 +21,6 @@ typedef struct kmem_cache kmem_cache_t __deprecated;
  * The ones marked DEBUG are only valid if CONFIG_SLAB_DEBUG is set.
  */
 #define SLAB_DEBUG_FREE         0x00000100UL    /* DEBUG: Perform (expensive) checks on free */
-#define SLAB_DEBUG_INITIAL      0x00000200UL    /* DEBUG: Call constructor (as verifier) */
 #define SLAB_RED_ZONE           0x00000400UL    /* DEBUG: Red zone objs in a cache */
 #define SLAB_POISON             0x00000800UL    /* DEBUG: Poison objects */
 #define SLAB_HWCACHE_ALIGN      0x00002000UL    /* Align objs on cache lines */
@@ -36,7 +35,6 @@ typedef struct kmem_cache kmem_cache_t __deprecated;
 /* Flags passed to a constructor functions */
 #define SLAB_CTOR_CONSTRUCTOR   0x001UL         /* If not set, then deconstructor */
 #define SLAB_CTOR_ATOMIC        0x002UL         /* Tell constructor it can't sleep */
-#define SLAB_CTOR_VERIFY        0x004UL         /* Tell constructor it's a verify call */
 
 /*
  * struct kmem_cache related prototypes