linux-kernel - [PATCHv3] powerpc: mm: radix_tlb: rearrange the if-else block

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Date:   Fri, 28 Jan 2022 14:17:13 +0100
From:   Anders Roxell <anders.roxell@...aro.org>
To:     nathan@...nel.org, ndesaulniers@...gle.com, mpe@...erman.id.au
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, christophe.leroy@...roup.eu,
        Anders Roxell <anders.roxell@...aro.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: [PATCHv3] powerpc: mm: radix_tlb: rearrange the if-else block

Clang warns:

arch/powerpc/mm/book3s64/radix_tlb.c:1191:23: error: variable 'hstart' is uninitialized when used here [-Werror,-Wuninitialized]
                                __tlbiel_va_range(hstart, hend, pid,
                                                  ^~~~~~
arch/powerpc/mm/book3s64/radix_tlb.c:1175:23: note: initialize the variable 'hstart' to silence this warning
                unsigned long hstart, hend;
                                    ^
                                     = 0
arch/powerpc/mm/book3s64/radix_tlb.c:1191:31: error: variable 'hend' is uninitialized when used here [-Werror,-Wuninitialized]
                                __tlbiel_va_range(hstart, hend, pid,
                                                          ^~~~
arch/powerpc/mm/book3s64/radix_tlb.c:1175:29: note: initialize the variable 'hend' to silence this warning
                unsigned long hstart, hend;
                                          ^
                                           = 0
2 errors generated.

Rework the 'if (IS_ENABLE(CONFIG_TRANSPARENT_HUGEPAGE))' so hstart/hend
always gets initialized, this will silence the warnings. That will also
simplify the 'else' path. Clang is getting confused with these warnings,
but the warnings is a false-positive.

Suggested-by: Arnd Bergmann <arnd@...db.de>
Suggested-by: Nathan Chancellor <nathan@...nel.org>
Reviewed-by: Christophe Leroy <christophe.leroy@...roup.eu>
Signed-off-by: Anders Roxell <anders.roxell@...aro.org>
---
 arch/powerpc/mm/book3s64/radix_tlb.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/mm/book3s64/radix_tlb.c b/arch/powerpc/mm/book3s64/radix_tlb.c
index 7724af19ed7e..5172d5cec2c0 100644
--- a/arch/powerpc/mm/book3s64/radix_tlb.c
+++ b/arch/powerpc/mm/book3s64/radix_tlb.c
@@ -1171,15 +1171,12 @@ static inline void __radix__flush_tlb_range(struct mm_struct *mm,
 			}
 		}
 	} else {
-		bool hflush = false;
+		bool hflush;
 		unsigned long hstart, hend;
 
-		if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
-			hstart = (start + PMD_SIZE - 1) & PMD_MASK;
-			hend = end & PMD_MASK;
-			if (hstart < hend)
-				hflush = true;
-		}
+		hstart = (start + PMD_SIZE - 1) & PMD_MASK;
+		hend = end & PMD_MASK;
+		hflush = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && hstart < hend;
 
 		if (type == FLUSH_TYPE_LOCAL) {
 			asm volatile("ptesync": : :"memory");
-- 
2.34.1