Re: [PATCH V9 5/7] KVM: guest_memfd: Add slab-allocated inode cache

On 7/13/25 19:43, Shivank Garg wrote:

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 | 58 ++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 56 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index dabcc2317291..989e2b26b344 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.

@@ -392,8 +401,33 @@ 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) @@ -426,17 +460,37 @@ 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;

• 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),
  

• 				  0, SLAB_ACCOUNT,
  

• 				  kvm_gmem_init_inode);
  

Since this is new code, please use the new variant of kmem_cache_create() that takes the args parameter.

• 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;

• kmem_cache_destroy(kvm_gmem_inode_cachep);

} static int kvm_gmem_migrate_folio(struct address_space *mapping,