linux-kernel - linux-next: build failure after merge of the kvm-x86 tree

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Date:   Mon, 30 Oct 2023 13:48:06 +1100
From:   Stephen Rothwell <sfr@...b.auug.org.au>
To:     Sean Christopherson <seanjc@...gle.com>,
        Christian Brauner <brauner@...nel.org>
Cc:     Ackerley Tng <ackerleytng@...gle.com>,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Isaku Yamahata <isaku.yamahata@...el.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Michael Roth <michael.roth@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: linux-next: build failure after merge of the kvm-x86 tree

Hi all,

After merging the kvm-x86 tree, today's linux-next build (x86_64
allmodconfig) failed like this:

arch/x86/kvm/../../../virt/kvm/guest_memfd.c: In function 'kvm_gmem_get_file':
arch/x86/kvm/../../../virt/kvm/guest_memfd.c:280:35: error: passing argument 1 of 'get_file_rcu' from incompatible pointer type [-Werror=incompatible-pointer-types]
  280 |         if (file && !get_file_rcu(file))
      |                                   ^~~~
      |                                   |
      |                                   struct file *
In file included from include/linux/backing-dev.h:13,
                 from arch/x86/kvm/../../../virt/kvm/guest_memfd.c:2:
include/linux/fs.h:1046:47: note: expected 'struct file **' but argument is of type 'struct file *'
 1046 | struct file *get_file_rcu(struct file __rcu **f);
      |                           ~~~~~~~~~~~~~~~~~~~~^

Caused by commit

  fcbef1e5e5d2 ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory")

interacting with commit

  0ede61d8589c ("file: convert to SLAB_TYPESAFE_BY_RCU")

from the vfs-brauner tree.

I have applied the following merg resolution patch:

From: Stephen Rothwell <sfr@...b.auug.org.au>
Date: Mon, 30 Oct 2023 13:35:38 +1100
Subject: [PATCH] fix up for "KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for
 guest-specific backing memory"

interacting with "file: convert to SLAB_TYPESAFE_BY_RCU"

Signed-off-by: Stephen Rothwell <sfr@...b.auug.org.au>
---
 virt/kvm/guest_memfd.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 94bc478c26f3..7f62abe3df9e 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -276,9 +276,7 @@ static struct file *kvm_gmem_get_file(struct kvm_memory_slot *slot)
 
 	rcu_read_lock();
 
-	file = rcu_dereference(slot->gmem.file);
-	if (file && !get_file_rcu(file))
-		file = NULL;
+	file = get_file_rcu(&slot->gmem.file);
 
 	rcu_read_unlock();
 
-- 
2.40.1

-- 
Cheers,
Stephen Rothwell

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