+ mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time-fix-3.patch added to -mm tree

+ mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time-fix-3.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time-fix-3
has been added to the -mm tree.  Its filename is
     mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time-fix-3.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-fix-3.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time-fix-3.patch

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------------------------------------------------------
From: Vlastimil Babka <vbabka@suse.cz>
Subject: mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time-fix-3

Kernel test robot reports a false-positive compile-time assert while compiling
kernel/bpf/local_storage.c

   In file included from <command-line>:
   In function 'kmalloc_index',
       inlined from 'kmalloc_node' at include/linux/slab.h:572:20,
       inlined from 'bpf_map_kmalloc_node.isra.0.part.0' at include/linux/bpf.h:1319:9:
>> >> include/linux/compiler_types.h:328:38: error: call to '__compiletime_assert_183' declared with attribute error: unexpected size in kmalloc_index()
     328 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
         |                                      ^
   include/linux/compiler_types.h:309:4: note: in definition of macro '__compiletime_assert'
     309 |    prefix ## suffix();    \
         |    ^~~~~~
   include/linux/compiler_types.h:328:2: note: in expansion of macro '_compiletime_assert'
     328 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
         |  ^~~~~~~~~~~~~~~~~~~
   include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
      39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
         |                                     ^~~~~~~~~~~~~~~~~~
   include/linux/slab.h:389:2: note: in expansion of macro 'BUILD_BUG_ON_MSG'
     389 |  BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()");
         |  ^~~~~~~~~~~~~~~~

This only happens with CONFIG_PROFILE_ALL_BRANCHES enabled.  Informal
conversation with gcc developers suggest that this config pushes the
optimizer to a corner case where in kmalloc_node() the 'size' is
considered a builtin-constant and thus kmalloc_index() is chosen, but
later in kmalloc_index() the notion of compile-time constant is lost and
thus the compiletime assert becomes reachable.

While there's plan to submit a proper gcc bug report with reduced
testcase, for now add CONFIG_PROFILE_ALL_BRANCHES to the list of
situations where we keep using the runtime BUG_ON() instead of
compile-time assert.

This is a 3rd fix for mmotm patch
mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time.patch

[1] https://lore.kernel.org/linux-mm/202106051442.G1VJubTz-lkp@intel.com/

Link: https://lkml.kernel.org/r/bea97388-01df-8eac-091b-a3c89b4a4a09@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: kernel test robot <lkp@intel.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
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 |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/include/linux/slab.h~mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time-fix-3
+++ a/include/linux/slab.h
@@ -389,7 +389,8 @@ static __always_inline unsigned int __km
 	if (size <=  16 * 1024 * 1024) return 24;
 	if (size <=  32 * 1024 * 1024) return 25;
 
-	if ((IS_ENABLED(CONFIG_CC_IS_GCC) || CONFIG_CLANG_VERSION >= 110000) && size_is_constant)
+	if ((IS_ENABLED(CONFIG_CC_IS_GCC) || CONFIG_CLANG_VERSION >= 110000)
+	    && !IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES) && size_is_constant)
 		BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()");
 	else
 		BUG();
_

Patches currently in -mm which might be from vbabka@suse.cz are

kunit-make-test-lock-irq-safe.patch
mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time-fix-3.patch
mm-memcg-slab-create-a-new-set-of-kmalloc-cg-n-caches-fix.patch
mm-slub-use-stackdepot-to-save-stack-trace-in-objects-fix-2.patch