linux-kernel - [PATCH] KVM: guest-memfd: fix unused-function warning

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Date:   Wed, 29 Nov 2023 16:32:40 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Isaku Yamahata <isaku.yamahata@...el.com>,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Sean Christopherson <seanjc@...gle.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: guest-memfd: fix unused-function warning

From: Arnd Bergmann <arnd@...db.de>

With migration disabled, one function becomes unused:

virt/kvm/guest_memfd.c:262:12: error: 'kvm_gmem_migrate_folio' defined but not used [-Werror=unused-function]
  262 | static int kvm_gmem_migrate_folio(struct address_space *mapping,
      |            ^~~~~~~~~~~~~~~~~~~~~~

Replace the #ifdef around the reference with a corresponding PTR_IF() check
that lets the compiler know how it is otherwise used.

Fixes: a7800aa80ea4 ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 virt/kvm/guest_memfd.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 16d58806e913..1a0355b95379 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -301,9 +301,8 @@ static int kvm_gmem_error_folio(struct address_space *mapping,
 
 static const struct address_space_operations kvm_gmem_aops = {
 	.dirty_folio = noop_dirty_folio,
-#ifdef CONFIG_MIGRATION
-	.migrate_folio	= kvm_gmem_migrate_folio,
-#endif
+	.migrate_folio = PTR_IF(IS_ENABLED(CONFIG_MIGRATION),
+				kvm_gmem_migrate_folio),
 	.error_remove_folio = kvm_gmem_error_folio,
 };
 
-- 
2.39.2