>+int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args)
>+{
>+ loff_t size = args->size;
>+ u64 flags = args->flags;
>+ u64 valid_flags = 0;
>+
>+ if (flags & ~valid_flags)
>+ return -EINVAL;
>+
>+ if (size < 0 || !PAGE_ALIGNED(size))
>+ return -EINVAL;
is size == 0 a valid case?
>+int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot,
>+ unsigned int fd, loff_t offset)
>+{
>+ loff_t size = slot->npages << PAGE_SHIFT;
>+ unsigned long start, end;
>+ struct kvm_gmem *gmem;
>+ struct inode *inode;
>+ struct file *file;
>+
>+ BUILD_BUG_ON(sizeof(gfn_t) != sizeof(slot->gmem.pgoff));
>+
>+ file = fget(fd);
>+ if (!file)
>+ return -EBADF;
>+
>+ if (file->f_op != &kvm_gmem_fops)
>+ goto err;
>+
>+ gmem = file->private_data;
>+ if (gmem->kvm != kvm)
>+ goto err;
>+
>+ inode = file_inode(file);
>+
>+ if (offset < 0 || !PAGE_ALIGNED(offset))
>+ return -EINVAL;
goto err;
or hoist the check above fget().
>+
>+ if (offset + size > i_size_read(inode))
>+ goto err;
>+
>+ filemap_invalidate_lock(inode->i_mapping);
>+
>+ start = offset >> PAGE_SHIFT;
>+ end = start + slot->npages;
>+
>+ if (!xa_empty(&gmem->bindings) &&
>+ xa_find(&gmem->bindings, &start, end - 1, XA_PRESENT)) {
>+ filemap_invalidate_unlock(inode->i_mapping);
>+ goto err;
>+ }
>+
>+ /*
>+ * No synchronize_rcu() needed, any in-flight readers are guaranteed to
>+ * be see either a NULL file or this new file, no need for them to go
>+ * away.
>+ */
>+ rcu_assign_pointer(slot->gmem.file, file);
>+ slot->gmem.pgoff = start;
>+
>+ xa_store_range(&gmem->bindings, start, end - 1, slot, GFP_KERNEL);
>+ filemap_invalidate_unlock(inode->i_mapping);
>+
>+ /*
>+ * Drop the reference to the file, even on success. The file pins KVM,
>+ * not the other way 'round. Active bindings are invalidated if the
>+ * file is closed before memslots are destroyed.
>+ */
>+ fput(file);
>+ return 0;
>+
>+err:
>+ fput(file);
>+ return -EINVAL;
The cleanup, i.e., filemap_invalidate_unlock() and fput(), is common. So, I think it
may be slightly better to consolidate the common part e.g.,
int ret = -EINVAL;
...
xa_store_range(&gmem->bindings, start, end - 1, slot, GFP_KERNEL);
ret = 0;
unlock:
filemap_invalidate_unlock(inode->i_mapping);
err:
/*
* Drop the reference to the file, even on success. The file pins KVM,
* not the other way 'round. Active bindings are invalidated if the
* file is closed before memslots are destroyed.
*/
fput(file);
return ret;
