[PATCH RFC 6/8] mm, slab: remove remaining compile-time checks for CONFIG_SLUB_TINY

["Vlastimil Babka (SUSE)" <vbabka@kernel.org>]

Remove several minor aspect of CONFIG_SLUB_TINY to allow it to be fully
a boot-time decision:

- remove check in cache_has_sheaves(), with no change to functionality
  but only on code elimination

- remove SLAB_SUPPORTS_SYSFS dependency on !CONFIG_SLUB_TINY, thus
  /sys/kernel/slab will exist as long as CONFIG_SYSFS is enabled
  (for now leave SLAB_SUPPORTS_SYSFS around, can be cleaned up later)

- remove the control of __fastpath_inline so it's just a wrapper of
  __always_inline. Leave it also around for documenting the intent, can
  be revisited later.

- remove a comment for SLAB_NO_MERGE as we don't want new checks for
  CONFIG_SLUB_TINY

This leaves the only usage of CONFIG_SLUB_TINY in slab code to set the
value of slab_tiny_enabled around.

net/core/skbuff.c keeps using it to control SLAB_NO_MERGE but that can
be dealt with independently after the config is deprecated.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 include/linux/slab.h | 2 +-
 mm/slab.h            | 7 +++----
 mm/slub.c            | 4 ----
 3 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 930dd64b9ad6..ad645967a3ee 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -188,7 +188,7 @@ enum _slab_flag_bits {
  * - general caches created and used by a subsystem, only when a
  *   (subsystem-specific) debug option is enabled
  * - performance critical caches, should be very rare and consulted with slab
- *   maintainers, and not used together with CONFIG_SLUB_TINY
+ *   maintainers
  */
 #define SLAB_NO_MERGE		__SLAB_FLAG_BIT(_SLAB_NO_MERGE)
 
diff --git a/mm/slab.h b/mm/slab.h
index 23017a5d10d1..065de2b92586 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -296,16 +296,15 @@ struct kmem_cache {
 /*
  * Every cache has !NULL s->cpu_sheaves but they may point to the
  * bootstrap_sheaf temporarily during init, or permanently for the boot caches
- * and caches with debugging enabled, or all caches with CONFIG_SLUB_TINY. This
+ * and caches with debugging enabled (or all caches with slab_tiny). This
  * helper distinguishes whether cache has real non-bootstrap sheaves.
  */
 static inline bool cache_has_sheaves(struct kmem_cache *s)
 {
-	/* Test CONFIG_SLUB_TINY for code elimination purposes */
-	return !IS_ENABLED(CONFIG_SLUB_TINY) && s->sheaf_capacity;
+	return s->sheaf_capacity;
 }
 
-#if defined(CONFIG_SYSFS) && !defined(CONFIG_SLUB_TINY)
+#ifdef CONFIG_SYSFS
 #define SLAB_SUPPORTS_SYSFS 1
 void sysfs_slab_unlink(struct kmem_cache *s);
 void sysfs_slab_release(struct kmem_cache *s);
diff --git a/mm/slub.c b/mm/slub.c
index c6a0422e055d..4814f025fde5 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -196,11 +196,7 @@ enum slab_flags {
 	SL_pfmemalloc = PG_active,	/* Historical reasons for this bit */
 };
 
-#ifndef CONFIG_SLUB_TINY
 #define __fastpath_inline __always_inline
-#else
-#define __fastpath_inline
-#endif
 
 DEFINE_STATIC_KEY_MAYBE(CONFIG_SLUB_DEBUG_ON, slub_debug_enabled);
 

-- 
2.55.0