linux-kernel - mm: ptl is not bloated if it fits in pointer

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Message-ID: <alpine.LNX.2.00.1312160053530.3066@eggly.anvils>
Date:	Mon, 16 Dec 2013 01:04:13 -0800 (PST)
From:	Hugh Dickins <hughd@...gle.com>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: mm: ptl is not bloated if it fits in pointer

It's silly to force the 64-bit CONFIG_GENERIC_LOCKBREAK architectures
to kmalloc eight bytes for an indirect page table lock: the lock needs
to fit in the space that a pointer to it would occupy, not into an int.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
---

 kernel/bounds.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 3.13-rc4/kernel/bounds.c	2013-11-22 15:40:37.452192638 -0800
+++ linux/kernel/bounds.c	2013-12-15 14:34:36.304485959 -0800
@@ -22,6 +22,6 @@ void foo(void)
 #ifdef CONFIG_SMP
 	DEFINE(NR_CPUS_BITS, ilog2(CONFIG_NR_CPUS));
 #endif
-	DEFINE(BLOATED_SPINLOCKS, sizeof(spinlock_t) > sizeof(int));
+	DEFINE(BLOATED_SPINLOCKS, sizeof(spinlock_t) > sizeof(spinlock_t *));
 	/* End of constants */
 }
--
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