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From: Yu Zhao <yuzhao@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Yu Zhao <yuzhao@google.com>
Subject: [PATCH 1/2] mm: correctly determine LAST_CPUPID_WIDTH
Date: Wed,  3 Mar 2021 00:16:08 -0700	[thread overview]
Message-ID: <20210303071609.797782-1-yuzhao@google.com> (raw)

The naming convention used in include/linux/page-flags-layout.h:
  *_SHIFT: the number of bits trying to allocate
  *_WIDTH: the number of bits successfully allocated

So when it comes to LAST_CPUPID_WIDTH, we need to check whether all
previous *_WIDTH and LAST_CPUPID_SHIFT can fit into page flags. This
means we need to use NODES_WIDTH, not NODES_SHIFT.

Signed-off-by: Yu Zhao <yuzhao@google.com>
---
 include/linux/page-flags-layout.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h
index 7d4ec26d8a3e..295c2c687d2c 100644
--- a/include/linux/page-flags-layout.h
+++ b/include/linux/page-flags-layout.h
@@ -83,7 +83,7 @@
 #define KASAN_TAG_WIDTH 0
 #endif
 
-#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT+KASAN_TAG_WIDTH \
+#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_WIDTH+LAST_CPUPID_SHIFT+KASAN_TAG_WIDTH \
 	<= BITS_PER_LONG - NR_PAGEFLAGS
 #define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
 #else
-- 
2.30.1.766.gb4fecdf3b7-goog


             reply	other threads:[~2021-03-03 12:58 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-03  7:16 Yu Zhao [this message]
2021-03-03  7:16 ` [PATCH 1/2] mm: correctly determine LAST_CPUPID_WIDTH Yu Zhao
2021-03-03  7:16 ` [PATCH 2/2] mm: clean up include/linux/page-flags-layout.h Yu Zhao
2021-03-03  7:16   ` Yu Zhao

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