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SubjectFAILED: Patch "bounds: support non-power-of-two CONFIG_NR_CPUS" failed to apply to 4.19-stable tree
Date
The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From f2d5dcb48f7ba9e3ff249d58fc1fa963d374e66a Mon Sep 17 00:00:00 2001
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Date: Tue, 10 Oct 2023 15:55:49 +0100
Subject: [PATCH] bounds: support non-power-of-two CONFIG_NR_CPUS

ilog2() rounds down, so for example when PowerPC 85xx sets CONFIG_NR_CPUS
to 24, we will only allocate 4 bits to store the number of CPUs instead of
5. Use bits_per() instead, which rounds up. Found by code inspection.
The effect of this would probably be a misaccounting when doing NUMA
balancing, so to a user, it would only be a performance penalty. The
effects may be more wide-spread; it's hard to tell.

Link: https://lkml.kernel.org/r/20231010145549.1244748-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Fixes: 90572890d202 ("mm: numa: Change page last {nid,pid} into {cpu,pid}")
Reviewed-by: Rik van Riel <riel@surriel.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
kernel/bounds.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bounds.c b/kernel/bounds.c
index b529182e8b04f..c5a9fcd2d6228 100644
--- a/kernel/bounds.c
+++ b/kernel/bounds.c
@@ -19,7 +19,7 @@ int main(void)
DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS);
DEFINE(MAX_NR_ZONES, __MAX_NR_ZONES);
#ifdef CONFIG_SMP
- DEFINE(NR_CPUS_BITS, ilog2(CONFIG_NR_CPUS));
+ DEFINE(NR_CPUS_BITS, bits_per(CONFIG_NR_CPUS));
#endif
DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t));
#ifdef CONFIG_LRU_GEN
--
2.43.0




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