drivers/misc/vmw_vmci/vmci_resource.c

   1 /*
   2  * VMware VMCI Driver
   3  *
   4  * Copyright (C) 2012 VMware, Inc. All rights reserved.
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the
   8  * Free Software Foundation version 2 and no later version.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  12  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * for more details.
  14  */
  15
  16 #include <linux/vmw_vmci_defs.h>
  17 #include <linux/hash.h>
  18 #include <linux/types.h>
  19 #include <linux/rculist.h>
  20 #include <linux/completion.h>
  21
  22 #include "vmci_resource.h"
  23 #include "vmci_driver.h"
  24
  25
  26 #define VMCI_RESOURCE_HASH_BITS         7
  27 #define VMCI_RESOURCE_HASH_BUCKETS      (1 << VMCI_RESOURCE_HASH_BITS)
  28
  29 struct vmci_hash_table {
  30         spinlock_t lock;
  31         struct hlist_head entries[VMCI_RESOURCE_HASH_BUCKETS];
  32 };
  33
  34 static struct vmci_hash_table vmci_resource_table = {
  35         .lock = __SPIN_LOCK_UNLOCKED(vmci_resource_table.lock),
  36 };
  37
  38 static unsigned int vmci_resource_hash(struct vmci_handle handle)
  39 {
  40         return hash_32(handle.resource, VMCI_RESOURCE_HASH_BITS);
  41 }
  42
  43 /*
  44  * Gets a resource (if one exists) matching given handle from the hash table.
  45  */
  46 static struct vmci_resource *vmci_resource_lookup(struct vmci_handle handle,
  47                                                   enum vmci_resource_type type)
  48 {
  49         struct vmci_resource *r, *resource = NULL;
  50         unsigned int idx = vmci_resource_hash(handle);
  51
  52         rcu_read_lock();
  53         hlist_for_each_entry_rcu(r,
  54                                  &vmci_resource_table.entries[idx], node) {
  55                 u32 cid = r->handle.context;
  56                 u32 rid = r->handle.resource;
  57
  58                 if (r->type == type &&
  59                     rid == handle.resource &&
  60                     (cid == handle.context || cid == VMCI_INVALID_ID)) {
  61                         resource = r;
  62                         break;
  63                 }
  64         }
  65         rcu_read_unlock();
  66
  67         return resource;
  68 }
  69
  70 /*
  71  * Find an unused resource ID and return it. The first
  72  * VMCI_RESERVED_RESOURCE_ID_MAX are reserved so we start from
  73  * its value + 1.
  74  * Returns VMCI resource id on success, VMCI_INVALID_ID on failure.
  75  */
  76 static u32 vmci_resource_find_id(u32 context_id,
  77                                  enum vmci_resource_type resource_type)
  78 {
  79         static u32 resource_id = VMCI_RESERVED_RESOURCE_ID_MAX + 1;
  80         u32 old_rid = resource_id;
  81         u32 current_rid;
  82
  83         /*
  84          * Generate a unique resource ID.  Keep on trying until we wrap around
  85          * in the RID space.
  86          */
  87         do {
  88                 struct vmci_handle handle;
  89
  90                 current_rid = resource_id;
  91                 resource_id++;
  92                 if (unlikely(resource_id == VMCI_INVALID_ID)) {
  93                         /* Skip the reserved rids. */
  94                         resource_id = VMCI_RESERVED_RESOURCE_ID_MAX + 1;
  95                 }
  96
  97                 handle = vmci_make_handle(context_id, current_rid);
  98                 if (!vmci_resource_lookup(handle, resource_type))
  99                         return current_rid;
 100         } while (resource_id != old_rid);
 101
 102         return VMCI_INVALID_ID;
 103 }
 104
 105
 106 int vmci_resource_add(struct vmci_resource *resource,
 107                       enum vmci_resource_type resource_type,
 108                       struct vmci_handle handle)
 109
 110 {
 111         unsigned int idx;
 112         int result;
 113
 114         spin_lock(&vmci_resource_table.lock);
 115
 116         if (handle.resource == VMCI_INVALID_ID) {
 117                 handle.resource = vmci_resource_find_id(handle.context,
 118                         resource_type);
 119                 if (handle.resource == VMCI_INVALID_ID) {
 120                         result = VMCI_ERROR_NO_HANDLE;
 121                         goto out;
 122                 }
 123         } else if (vmci_resource_lookup(handle, resource_type)) {
 124                 result = VMCI_ERROR_ALREADY_EXISTS;
 125                 goto out;
 126         }
 127
 128         resource->handle = handle;
 129         resource->type = resource_type;
 130         INIT_HLIST_NODE(&resource->node);
 131         kref_init(&resource->kref);
 132         init_completion(&resource->done);
 133
 134         idx = vmci_resource_hash(resource->handle);
 135         hlist_add_head_rcu(&resource->node, &vmci_resource_table.entries[idx]);
 136
 137         result = VMCI_SUCCESS;
 138
 139 out:
 140         spin_unlock(&vmci_resource_table.lock);
 141         return result;
 142 }
 143
 144 void vmci_resource_remove(struct vmci_resource *resource)
 145 {
 146         struct vmci_handle handle = resource->handle;
 147         unsigned int idx = vmci_resource_hash(handle);
 148         struct vmci_resource *r;
 149
 150         /* Remove resource from hash table. */
 151         spin_lock(&vmci_resource_table.lock);
 152
 153         hlist_for_each_entry(r, &vmci_resource_table.entries[idx], node) {
 154                 if (vmci_handle_is_equal(r->handle, resource->handle)) {
 155                         hlist_del_init_rcu(&r->node);
 156                         break;
 157                 }
 158         }
 159
 160         spin_unlock(&vmci_resource_table.lock);
 161         synchronize_rcu();
 162
 163         vmci_resource_put(resource);
 164         wait_for_completion(&resource->done);
 165 }
 166
 167 struct vmci_resource *
 168 vmci_resource_by_handle(struct vmci_handle resource_handle,
 169                         enum vmci_resource_type resource_type)
 170 {
 171         struct vmci_resource *r, *resource = NULL;
 172
 173         rcu_read_lock();
 174
 175         r = vmci_resource_lookup(resource_handle, resource_type);
 176         if (r &&
 177             (resource_type == r->type ||
 178              resource_type == VMCI_RESOURCE_TYPE_ANY)) {
 179                 resource = vmci_resource_get(r);
 180         }
 181
 182         rcu_read_unlock();
 183
 184         return resource;
 185 }
 186
 187 /*
 188  * Get a reference to given resource.
 189  */
 190 struct vmci_resource *vmci_resource_get(struct vmci_resource *resource)
 191 {
 192         kref_get(&resource->kref);
 193
 194         return resource;
 195 }
 196
 197 static void vmci_release_resource(struct kref *kref)
 198 {
 199         struct vmci_resource *resource =
 200                 container_of(kref, struct vmci_resource, kref);
 201
 202         /* Verify the resource has been unlinked from hash table */
 203         WARN_ON(!hlist_unhashed(&resource->node));
 204
 205         /* Signal that container of this resource can now be destroyed */
 206         complete(&resource->done);
 207 }
 208
 209 /*
 210  * Resource's release function will get called if last reference.
 211  * If it is the last reference, then we are sure that nobody else
 212  * can increment the count again (it's gone from the resource hash
 213  * table), so there's no need for locking here.
 214  */
 215 int vmci_resource_put(struct vmci_resource *resource)
 216 {
 217         /*
 218          * We propagate the information back to caller in case it wants to know
 219          * whether entry was freed.
 220          */
 221         return kref_put(&resource->kref, vmci_release_resource) ?
 222                 VMCI_SUCCESS_ENTRY_DEAD : VMCI_SUCCESS;
 223 }
 224
 225 struct vmci_handle vmci_resource_handle(struct vmci_resource *resource)
 226 {
 227         return resource->handle;
 228 }