linux-kernel - [PATCH v2] x86/mm: fix "old

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Message-Id: <20190301152924.94762-1-cai@lca.pw>
Date:   Fri,  1 Mar 2019 10:29:24 -0500
From:   Qian Cai <cai@....pw>
To:     dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org
Cc:     toshi.kani@....com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, hpa@...or.com, x86@...nel.org,
        linux-kernel@...r.kernel.org, Qian Cai <cai@....pw>
Subject: [PATCH v2] x86/mm: fix "old_pte" set but not used

The commit 3a19109efbfa ("x86/mm: Fix try_preserve_large_page() to
handle large PAT bit") fixed try_preserve_large_page() by using the
corresponding pud/pmd prot/pfn interfaces, but left a variable unused
because it no longer used pte_pfn().

Later, the commit 8679de0959e6 ("x86/mm/cpa: Split, rename and clean up
try_preserve_large_page()") renamed try_preserve_large_page() to
__should_split_large_page(), but the unused variable remains.

arch/x86/mm/pageattr.c: In function '__should_split_large_page':
arch/x86/mm/pageattr.c:741:17: warning: variable 'old_pte' set but not
used [-Wunused-but-set-variable]

Signed-off-by: Qian Cai <cai@....pw>
---

v2: improve the commit message.

 arch/x86/mm/pageattr.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 14e6119838a6..4c570612e24e 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -738,7 +738,7 @@ static int __should_split_large_page(pte_t *kpte, unsigned long address,
 {
 	unsigned long numpages, pmask, psize, lpaddr, pfn, old_pfn;
 	pgprot_t old_prot, new_prot, req_prot, chk_prot;
-	pte_t new_pte, old_pte, *tmp;
+	pte_t new_pte, *tmp;
 	enum pg_level level;
 
 	/*
@@ -781,7 +781,7 @@ static int __should_split_large_page(pte_t *kpte, unsigned long address,
 	 * Convert protection attributes to 4k-format, as cpa->mask* are set
 	 * up accordingly.
 	 */
-	old_pte = *kpte;
+
 	/* Clear PSE (aka _PAGE_PAT) and move PAT bit to correct position */
 	req_prot = pgprot_large_2_4k(old_prot);
 
-- 
2.17.2 (Apple Git-113)