On 10/18/2025 4:11 AM, Ackerley Tng wrote: [...]
+static int kvm_gmem_init_inode(struct inode *inode, loff_t size, u64 flags) +{
- struct gmem_inode *gi = GMEM_I(inode);
- MA_STATE(mas, &gi->attributes, 0, (size >> PAGE_SHIFT) - 1);
- u64 attrs;
- int r;
- inode->i_op = &kvm_gmem_iops;
- inode->i_mapping->a_ops = &kvm_gmem_aops;
- inode->i_mode |= S_IFREG;
- inode->i_size = size;
- mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
- mapping_set_inaccessible(inode->i_mapping);
- /* Unmovable mappings are supposed to be marked unevictable as well. */
AS_UNMOVABLE has been removed and got merged into AS_INACCESSIBLE, not sure if it's better to use "Inaccessible" instead of "Unmovable"
- WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping));
- gi->flags = flags;
- mt_set_external_lock(&gi->attributes,
&inode->i_mapping->invalidate_lock);- /*
* Store default attributes for the entire gmem instance. Ensuring every* index is represented in the maple tree at all times simplifies the* conversion and merging logic.*/- attrs = gi->flags & GUEST_MEMFD_FLAG_INIT_SHARED ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE;
- /*
* Acquire the invalidation lock purely to make lockdep happy. There* should be no races at this time since the inode hasn't yet been fully* created.*/- filemap_invalidate_lock(inode->i_mapping);
- r = mas_store_gfp(&mas, xa_mk_value(attrs), GFP_KERNEL);
- filemap_invalidate_unlock(inode->i_mapping);
- return r;
+}
[...]
@@ -925,13 +986,39 @@ static struct inode *kvm_gmem_alloc_inode(struct super_block *sb)
mpol_shared_policy_init(&gi->policy, NULL);
- /*
* Memory attributes are protected the filemap invalidation lock, but
^ protected by
* the lock structure isn't available at this time. Immediately mark* maple tree as using external locking so that accessing the tree* before its fully initialized results in NULL pointer dereferences* and not more subtle bugs.*/mt_init_flags(&gi->attributes, MT_FLAGS_LOCK_EXTERN);
gi->flags = 0; return &gi->vfs_inode; }
static void kvm_gmem_destroy_inode(struct inode *inode) {
- mpol_free_shared_policy(&GMEM_I(inode)->policy);
- struct gmem_inode *gi = GMEM_I(inode);
- mpol_free_shared_policy(&gi->policy);
- /*
* Note! Checking for an empty tree is functionally necessary to avoid* explosions if the tree hasn't been initialized, i.e. if the inode is
It makes sense to skip __mt_destroy() when mtree is empty. But what explosions it could trigger if mtree is empty? It seems __mt_destroy() can handle the case if the external lock is not set.
* being destroyed before guest_memfd can set the external lock.*/if (!mtree_empty(&gi->attributes)) {
/** Acquire the invalidation lock purely to make lockdep happy,* the inode is unreachable at this point.*/filemap_invalidate_lock(inode->i_mapping);__mt_destroy(&gi->attributes);filemap_invalidate_unlock(inode->i_mapping);} }
static void kvm_gmem_free_inode(struct inode *inode)
-- 2.51.0.858.gf9c4a03a3a-goog