linux-kernel - [PATCH] mm: fix vm_fault_t cast in VM_FAULT_GET

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Message-Id: <20190327204117.35215-1-jannh@google.com>
Date:   Wed, 27 Mar 2019 21:41:17 +0100
From:   Jann Horn <jannh@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>, jannh@...gle.com
Cc:     Souptick Joarder <jrdr.linux@...il.com>,
        Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Rik van Riel <riel@...riel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH] mm: fix vm_fault_t cast in VM_FAULT_GET_HINDEX()

Symmetrically to VM_FAULT_SET_HINDEX(), we need a force-cast in
VM_FAULT_GET_HINDEX() to tell sparse that this is intentional.

Sparse complains about the current code when building a kernel with
CONFIG_MEMORY_FAILURE:

arch/x86/mm/fault.c:1058:53: warning: restricted vm_fault_t degrades to
integer

Fixes: 3d3539018d2c ("mm: create the new vm_fault_t type")
Signed-off-by: Jann Horn <jannh@...gle.com>
---
 include/linux/mm_types.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 7eade9132f02..4ef4bbe78a1d 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -671,7 +671,7 @@ enum vm_fault_reason {
 
 /* Encode hstate index for a hwpoisoned large page */
 #define VM_FAULT_SET_HINDEX(x) ((__force vm_fault_t)((x) << 16))
-#define VM_FAULT_GET_HINDEX(x) (((x) >> 16) & 0xf)
+#define VM_FAULT_GET_HINDEX(x) (((__force unsigned int)(x) >> 16) & 0xf)
 
 #define VM_FAULT_ERROR (VM_FAULT_OOM | VM_FAULT_SIGBUS |	\
 			VM_FAULT_SIGSEGV | VM_FAULT_HWPOISON |	\
-- 
2.21.0.392.gf8f6787159e-goog