+ mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time.patch added to -mm tree

* + mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time.patch added to -mm tree
@ 2021-05-13 22:33 akpm
  0 siblings, 0 replies; 2+ messages in thread
From: akpm @ 2021-05-13 22:33 UTC (permalink / raw)
  To: 42.hyeyoo, cl, elver, iamjoonsoo.kim, mm-commits, penberg,
	rientjes, vbabka


The patch titled
     Subject: mm, slub: change run-time assertion in kmalloc_index() to compile-time
has been added to the -mm tree.  Its filename is
     mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time.patch

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------------------------------------------------------
From: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Subject: mm, slub: change run-time assertion in kmalloc_index() to compile-time

Currently when size is not supported by kmalloc_index, compiler will
generate a run-time BUG() while compile-time error is also possible, and
better.  So change BUG to BUILD_BUG_ON_MSG to make compile-time check
possible.

Also remove code that allocates more than 32MB because current
implementation supports only up to 32MB.

Link: https://lkml.kernel.org/r/20210511173448.GA54466@hyeyoo
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
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: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/slab.h |    7 +++++--
 mm/slab_common.c     |    7 +++----
 2 files changed, 8 insertions(+), 6 deletions(-)

--- a/include/linux/slab.h~mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time
+++ a/include/linux/slab.h
@@ -346,6 +346,9 @@ static __always_inline enum kmalloc_cach
  * 1 =  65 .. 96 bytes
  * 2 = 129 .. 192 bytes
  * n = 2^(n-1)+1 .. 2^n
+ *
+ * Note: there's no need to optimize kmalloc_index because it's evaluated
+ * in compile-time.
  */
 static __always_inline unsigned int kmalloc_index(size_t size)
 {
@@ -382,8 +385,8 @@ static __always_inline unsigned int kmal
 	if (size <=  8 * 1024 * 1024) return 23;
 	if (size <=  16 * 1024 * 1024) return 24;
 	if (size <=  32 * 1024 * 1024) return 25;
-	if (size <=  64 * 1024 * 1024) return 26;
-	BUG();
+
+	BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()");
 
 	/* Will never be reached. Needed because the compiler may complain */
 	return -1;
--- a/mm/slab_common.c~mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time
+++ a/mm/slab_common.c
@@ -755,8 +755,8 @@ struct kmem_cache *kmalloc_slab(size_t s
 
 /*
  * kmalloc_info[] is to make slub_debug=,kmalloc-xx option work at boot time.
- * kmalloc_index() supports up to 2^26=64MB, so the final entry of the table is
- * kmalloc-67108864.
+ * kmalloc_index() supports up to 2^25=32MB, so the final entry of the table is
+ * kmalloc-32M.
  */
 const struct kmalloc_info_struct kmalloc_info[] __initconst = {
 	INIT_KMALLOC_INFO(0, 0),
@@ -784,8 +784,7 @@ const struct kmalloc_info_struct kmalloc
 	INIT_KMALLOC_INFO(4194304, 4M),
 	INIT_KMALLOC_INFO(8388608, 8M),
 	INIT_KMALLOC_INFO(16777216, 16M),
-	INIT_KMALLOC_INFO(33554432, 32M),
-	INIT_KMALLOC_INFO(67108864, 64M)
+	INIT_KMALLOC_INFO(33554432, 32M)
 };
 
 /*
_

Patches currently in -mm which might be from 42.hyeyoo@gmail.com are

mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time.patch
mm-fix-typos-and-grammar-error-in-comments.patch


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