[PATCH kvm-next V11 5/7] KVM: guest_memfd: Add slab-allocated inode cache

Shivank Garg
2025-08-27T17:57:14Z

Add dedicated inode structure (kvm_gmem_inode_info) and slab-allocated
inode cache for guest memory backing, similar to how shmem handles inodes.

This adds the necessary allocation/destruction functions and prepares
for upcoming guest_memfd NUMA policy support changes.

Signed-off-by: Shivank Garg <shivankg@amd.com>
---
virt/kvm/guest_memfd.c | 70 ++++++++++++++++++++++++++++++++++++++++--
1 file changed, 68 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 6c66a0974055..356947d36a47 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -17,6 +17,15 @@ struct kvm_gmem {
struct list_head entry;
};

+struct kvm_gmem_inode_info {
+ struct inode vfs_inode;
+};
+
+static inline struct kvm_gmem_inode_info *KVM_GMEM_I(struct inode *inode)
+{
+ return container_of(inode, struct kvm_gmem_inode_info, vfs_inode);
+}
+
/**
* folio_file_pfn - like folio_file_page, but return a pfn.
* @folio: The folio which contains this index.
@@ -389,13 +398,46 @@ static struct file_operations kvm_gmem_fops = {
.fallocate = kvm_gmem_fallocate,
};

+static struct kmem_cache *kvm_gmem_inode_cachep;
+
+static struct inode *kvm_gmem_alloc_inode(struct super_block *sb)
+{
+ struct kvm_gmem_inode_info *info;
+
+ info = alloc_inode_sb(sb, kvm_gmem_inode_cachep, GFP_KERNEL);
+ if (!info)
+ return NULL;
+
+ return &info->vfs_inode;
+}
+
+static void kvm_gmem_destroy_inode(struct inode *inode)
+{
+}
+
+static void kvm_gmem_free_inode(struct inode *inode)
+{
+ kmem_cache_free(kvm_gmem_inode_cachep, KVM_GMEM_I(inode));
+}
+
+static const struct super_operations kvm_gmem_super_operations = {
+ .statfs = simple_statfs,
+ .alloc_inode = kvm_gmem_alloc_inode,
+ .destroy_inode = kvm_gmem_destroy_inode,
+ .free_inode = kvm_gmem_free_inode,
+};
+
static int kvm_gmem_init_fs_context(struct fs_context *fc)
{
+ struct pseudo_fs_context *ctx;
+
if (!init_pseudo(fc, GUEST_MEMFD_MAGIC))
return -ENOMEM;

fc->s_iflags |= SB_I_NOEXEC;
fc->s_iflags |= SB_I_NODEV;
+ ctx = fc->fs_private;
+ ctx->ops = &kvm_gmem_super_operations;

return 0;
}
@@ -417,17 +459,41 @@ static int kvm_gmem_init_mount(void)
return 0;
}

+static void kvm_gmem_init_inode(void *foo)
+{
+ struct kvm_gmem_inode_info *info = foo;
+
+ inode_init_once(&info->vfs_inode);
+}
+
int kvm_gmem_init(struct module *module)
{
- kvm_gmem_fops.owner = module;
+ int ret;
+ struct kmem_cache_args args = {
+ .align = 0,
+ .ctor = kvm_gmem_init_inode,
+ };

- return kvm_gmem_init_mount();
+ kvm_gmem_fops.owner = module;
+ kvm_gmem_inode_cachep = kmem_cache_create("kvm_gmem_inode_cache",
+ sizeof(struct kvm_gmem_inode_info),
+ &args, SLAB_ACCOUNT);
+ if (!kvm_gmem_inode_cachep)
+ return -ENOMEM;
+ ret = kvm_gmem_init_mount();
+ if (ret) {
+ kmem_cache_destroy(kvm_gmem_inode_cachep);
+ return ret;
+ }
+ return 0;
}

void kvm_gmem_exit(void)
{
kern_unmount(kvm_gmem_mnt);
kvm_gmem_mnt = NULL;
+ rcu_barrier();
+ kmem_cache_destroy(kvm_gmem_inode_cachep);
}

static int kvm_gmem_migrate_folio(struct address_space *mapping,
--
2.43.0