VMCI: resource object implementation.

VMCI resource tracks all used resources within the vmci code.

Signed-off-by: George Zhang <georgezhang@vmware.com>
Acked-by: Andy king <acking@vmware.com>
Acked-by: Dmitry Torokhov <dtor@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 229 insertions, 0 deletions

diff --git a/drivers/misc/vmw_vmci/vmci_resource.c b/drivers/misc/vmw_vmci/vmci_resource.c
new file mode 100644
index 000000000000..a196f84a4fd2
--- /dev/null
+++ b/drivers/misc/vmw_vmci/vmci_resource.c
@@ -0,0 +1,229 @@
+/*
+ * VMware VMCI Driver
+ *
+ * Copyright (C) 2012 VMware, Inc. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation version 2 and no later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ */
+
+#include <linux/vmw_vmci_defs.h>
+#include <linux/hash.h>
+#include <linux/types.h>
+#include <linux/rculist.h>
+
+#include "vmci_resource.h"
+#include "vmci_driver.h"
+
+
+#define VMCI_RESOURCE_HASH_BITS         7
+#define VMCI_RESOURCE_HASH_BUCKETS      (1 << VMCI_RESOURCE_HASH_BITS)
+
+struct vmci_hash_table {
+        spinlock_t lock;
+        struct hlist_head entries[VMCI_RESOURCE_HASH_BUCKETS];
+};
+
+static struct vmci_hash_table vmci_resource_table = {
+        .lock = __SPIN_LOCK_UNLOCKED(vmci_resource_table.lock),
+};
+
+static unsigned int vmci_resource_hash(struct vmci_handle handle)
+{
+        return hash_32(handle.resource, VMCI_RESOURCE_HASH_BITS);
+}
+
+/*
+ * Gets a resource (if one exists) matching given handle from the hash table.
+ */
+static struct vmci_resource *vmci_resource_lookup(struct vmci_handle handle,
+                                                  enum vmci_resource_type type)
+{
+        struct vmci_resource *r, *resource = NULL;
+        struct hlist_node *node;
+        unsigned int idx = vmci_resource_hash(handle);
+
+        rcu_read_lock();
+        hlist_for_each_entry_rcu(r, node,
+                                 &vmci_resource_table.entries[idx], node) {
+                u32 cid = r->handle.context;
+                u32 rid = r->handle.resource;
+
+                if (r->type == type &&
+                    rid == handle.resource &&
+                    (cid == handle.context || cid == VMCI_INVALID_ID)) {
+                        resource = r;
+                        break;
+                }
+        }
+        rcu_read_unlock();
+
+        return resource;
+}
+
+/*
+ * Find an unused resource ID and return it. The first
+ * VMCI_RESERVED_RESOURCE_ID_MAX are reserved so we start from
+ * its value + 1.
+ * Returns VMCI resource id on success, VMCI_INVALID_ID on failure.
+ */
+static u32 vmci_resource_find_id(u32 context_id,
+                                 enum vmci_resource_type resource_type)
+{
+        static u32 resource_id = VMCI_RESERVED_RESOURCE_ID_MAX + 1;
+        u32 old_rid = resource_id;
+        u32 current_rid;
+
+        /*
+         * Generate a unique resource ID.  Keep on trying until we wrap around
+         * in the RID space.
+         */
+        do {
+                struct vmci_handle handle;
+
+                current_rid = resource_id;
+                resource_id++;
+                if (unlikely(resource_id == VMCI_INVALID_ID)) {
+                        /* Skip the reserved rids. */
+                        resource_id = VMCI_RESERVED_RESOURCE_ID_MAX + 1;
+                }
+
+                handle = vmci_make_handle(context_id, current_rid);
+                if (!vmci_resource_lookup(handle, resource_type))
+                        return current_rid;
+        } while (resource_id != old_rid);
+
+        return VMCI_INVALID_ID;
+}
+
+
+int vmci_resource_add(struct vmci_resource *resource,
+                      enum vmci_resource_type resource_type,
+                      struct vmci_handle handle)
+
+{
+        unsigned int idx;
+        int result;
+
+        spin_lock(&vmci_resource_table.lock);
+
+        if (handle.resource == VMCI_INVALID_ID) {
+                handle.resource = vmci_resource_find_id(handle.context,
+                        resource_type);
+                if (handle.resource == VMCI_INVALID_ID) {
+                        result = VMCI_ERROR_NO_HANDLE;
+                        goto out;
+                }
+        } else if (vmci_resource_lookup(handle, resource_type)) {
+                result = VMCI_ERROR_ALREADY_EXISTS;
+                goto out;
+        }
+
+        resource->handle = handle;
+        resource->type = resource_type;
+        INIT_HLIST_NODE(&resource->node);
+        kref_init(&resource->kref);
+        init_completion(&resource->done);
+
+        idx = vmci_resource_hash(resource->handle);
+        hlist_add_head_rcu(&resource->node, &vmci_resource_table.entries[idx]);
+
+        result = VMCI_SUCCESS;
+
+out:
+        spin_unlock(&vmci_resource_table.lock);
+        return result;
+}
+
+void vmci_resource_remove(struct vmci_resource *resource)
+{
+        struct vmci_handle handle = resource->handle;
+        unsigned int idx = vmci_resource_hash(handle);
+        struct vmci_resource *r;
+        struct hlist_node *node;
+
+        /* Remove resource from hash table. */
+        spin_lock(&vmci_resource_table.lock);
+
+        hlist_for_each_entry(r, node, &vmci_resource_table.entries[idx], node) {
+                if (vmci_handle_is_equal(r->handle, resource->handle)) {
+                        hlist_del_init_rcu(&r->node);
+                        break;
+                }
+        }
+
+        spin_unlock(&vmci_resource_table.lock);
+        synchronize_rcu();
+
+        vmci_resource_put(resource);
+        wait_for_completion(&resource->done);
+}
+
+struct vmci_resource *
+vmci_resource_by_handle(struct vmci_handle resource_handle,
+                        enum vmci_resource_type resource_type)
+{
+        struct vmci_resource *r, *resource = NULL;
+
+        rcu_read_lock();
+
+        r = vmci_resource_lookup(resource_handle, resource_type);
+        if (r &&
+            (resource_type == r->type ||
+             resource_type == VMCI_RESOURCE_TYPE_ANY)) {
+                resource = vmci_resource_get(r);
+        }
+
+        rcu_read_unlock();
+
+        return resource;
+}
+
+/*
+ * Get a reference to given resource.
+ */
+struct vmci_resource *vmci_resource_get(struct vmci_resource *resource)
+{
+        kref_get(&resource->kref);
+
+        return resource;
+}
+
+static void vmci_release_resource(struct kref *kref)
+{
+        struct vmci_resource *resource =
+                container_of(kref, struct vmci_resource, kref);
+
+        /* Verify the resource has been unlinked from hash table */
+        WARN_ON(!hlist_unhashed(&resource->node));
+
+        /* Signal that container of this resource can now be destroyed */
+        complete(&resource->done);
+}
+
+/*
+ * Resource's release function will get called if last reference.
+ * If it is the last reference, then we are sure that nobody else
+ * can increment the count again (it's gone from the resource hash
+ * table), so there's no need for locking here.
+ */
+int vmci_resource_put(struct vmci_resource *resource)
+{
+        /*
+         * We propagate the information back to caller in case it wants to know
+         * whether entry was freed.
+         */
+        return kref_put(&resource->kref, vmci_release_resource) ?
+                VMCI_SUCCESS_ENTRY_DEAD : VMCI_SUCCESS;
+}
+
+struct vmci_handle vmci_resource_handle(struct vmci_resource *resource)
+{
+        return resource->handle;
+}