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Tue, 24 Jun 2025 12:16:08 +0800 From: "Huang, Ying" To: Shivank Garg Cc: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [RFC PATCH v8 5/7] KVM: guest_memfd: Add slab-allocated inode cache In-Reply-To: <20250618112935.7629-6-shivankg@amd.com> (Shivank Garg's message of "Wed, 18 Jun 2025 11:29:33 +0000") References: <20250618112935.7629-1-shivankg@amd.com> <20250618112935.7629-6-shivankg@amd.com> Date: Tue, 24 Jun 2025 12:16:06 +0800 Message-ID: <87ecv9ojuh.fsf@DESKTOP-5N7EMDA> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Shivank Garg writes: > 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 > --- > virt/kvm/guest_memfd.c | 51 ++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 51 insertions(+) > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index 159df462d193..5a1ce6f5e287 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) > @@ -426,10 +460,26 @@ 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); > +} > + > +static void kvm_gmem_init_inodecache(void) > +{ > + kvm_gmem_inode_cachep = kmem_cache_create("kvm_gmem_inode_cache", > + sizeof(struct kvm_gmem_inode_info), > + 0, SLAB_ACCOUNT, > + kvm_gmem_init_inode); Check the return value? And, I'm not a big fan of (logically) one line function encapsulation. > +} > + > int kvm_gmem_init(struct module *module) > { > kvm_gmem_fops.owner = module; > > + kvm_gmem_init_inodecache(); > return kvm_gmem_init_mount(); kmem_cache_destroy(kvm_gmem_inode_cachep) if kvm_gmem_init_mount() return with error? > } > > @@ -437,6 +487,7 @@ 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, --- Best Regards, Huang, Ying