drivers/md/dm-memcache.c

   1 /*
   2  * Copyright (C) 2006-2008 Red Hat, Inc. All rights reserved.
   3  *
   4  * Module Author: Heinz Mauelshagen <heinzm@redhat.com>
   5  *
   6  * Device-mapper memory object handling:
   7  *
   8  * o allocate/free total_pages in a per client page pool.
   9  *
  10  * o allocate/free memory objects with chunks (1..n) of
  11  *   pages_per_chunk pages hanging off.
  12  *
  13  * This file is released under the GPL.
  14  */
  15
  16 #define DM_MEM_CACHE_VERSION    "0.2"
  17
  18 #include "dm.h"
  19 #include "dm-memcache.h"
  20 #include <linux/dm-io.h>
  21 #include <linux/slab.h>
  22 #include <linux/module.h>
  23
  24 struct dm_mem_cache_client {
  25         spinlock_t lock;
  26         mempool_t *objs_pool;
  27         struct page_list *free_list;
  28         unsigned objects;
  29         unsigned chunks;
  30         unsigned pages_per_chunk;
  31         unsigned free_pages;
  32         unsigned total_pages;
  33 };
  34
  35 /*
  36  * Free pages and page_list elements of client.
  37  */
  38 static void free_cache_pages(struct page_list *list)
  39 {
  40         while (list) {
  41                 struct page_list *pl = list;
  42
  43                 list = pl->next;
  44                 BUG_ON(!pl->page);
  45                 __free_page(pl->page);
  46                 kfree(pl);
  47         }
  48 }
  49
  50 /*
  51  * Alloc number of pages and page_list elements as required by client.
  52  */
  53 static struct page_list *alloc_cache_pages(unsigned pages)
  54 {
  55         struct page_list *pl, *ret = NULL;
  56         struct page *page;
  57
  58         while (pages--) {
  59                 page = alloc_page(GFP_NOIO);
  60                 if (!page)
  61                         goto err;
  62
  63                 pl = kmalloc(sizeof(*pl), GFP_NOIO);
  64                 if (!pl) {
  65                         __free_page(page);
  66                         goto err;
  67                 }
  68
  69                 pl->page = page;
  70                 pl->next = ret;
  71                 ret = pl;
  72         }
  73
  74         return ret;
  75
  76 err:
  77         free_cache_pages(ret);
  78         return NULL;
  79 }
  80
  81 /*
  82  * Allocate page_list elements from the pool to chunks of the memory object.
  83  */
  84 static void alloc_chunks(struct dm_mem_cache_client *cl,
  85                          struct dm_mem_cache_object *obj)
  86 {
  87         unsigned chunks = cl->chunks;
  88         unsigned long flags;
  89
  90         local_irq_save(flags);
  91         local_irq_disable();
  92         while (chunks--) {
  93                 unsigned p = cl->pages_per_chunk;
  94
  95                 obj[chunks].pl = NULL;
  96
  97                 while (p--) {
  98                         struct page_list *pl;
  99
 100                         /* Take next element from free list */
 101                         spin_lock(&cl->lock);
 102                         pl = cl->free_list;
 103                         BUG_ON(!pl);
 104                         cl->free_list = pl->next;
 105                         spin_unlock(&cl->lock);
 106
 107                         pl->next = obj[chunks].pl;
 108                         obj[chunks].pl = pl;
 109                 }
 110         }
 111
 112         local_irq_restore(flags);
 113 }
 114
 115 /*
 116  * Free page_list elements putting them back onto free list
 117  */
 118 static void free_chunks(struct dm_mem_cache_client *cl,
 119                         struct dm_mem_cache_object *obj)
 120 {
 121         unsigned chunks = cl->chunks;
 122         unsigned long flags;
 123         struct page_list *next, *pl;
 124
 125         local_irq_save(flags);
 126         local_irq_disable();
 127         while (chunks--) {
 128                 for (pl = obj[chunks].pl; pl; pl = next) {
 129                         next = pl->next;
 130
 131                         spin_lock(&cl->lock);
 132                         pl->next = cl->free_list;
 133                         cl->free_list = pl;
 134                         cl->free_pages++;
 135                         spin_unlock(&cl->lock);
 136                 }
 137         }
 138
 139         local_irq_restore(flags);
 140 }
 141
 142 /*
 143  * Create/destroy dm memory cache client resources.
 144  */
 145 struct dm_mem_cache_client *
 146 dm_mem_cache_client_create(unsigned objects, unsigned chunks,
 147                            unsigned pages_per_chunk)
 148 {
 149         unsigned total_pages = objects * chunks * pages_per_chunk;
 150         struct dm_mem_cache_client *client;
 151
 152         BUG_ON(!total_pages);
 153         client = kzalloc(sizeof(*client), GFP_KERNEL);
 154         if (!client)
 155                 return ERR_PTR(-ENOMEM);
 156
 157         client->objs_pool = mempool_create_kmalloc_pool(objects,
 158                                 chunks * sizeof(struct dm_mem_cache_object));
 159         if (!client->objs_pool)
 160                 goto err;
 161
 162         client->free_list = alloc_cache_pages(total_pages);
 163         if (!client->free_list)
 164                 goto err1;
 165
 166         spin_lock_init(&client->lock);
 167         client->objects = objects;
 168         client->chunks = chunks;
 169         client->pages_per_chunk = pages_per_chunk;
 170         client->free_pages = client->total_pages = total_pages;
 171         return client;
 172
 173 err1:
 174         mempool_destroy(client->objs_pool);
 175 err:
 176         kfree(client);
 177         return ERR_PTR(-ENOMEM);
 178 }
 179 EXPORT_SYMBOL(dm_mem_cache_client_create);
 180
 181 void dm_mem_cache_client_destroy(struct dm_mem_cache_client *cl)
 182 {
 183         BUG_ON(cl->free_pages != cl->total_pages);
 184         free_cache_pages(cl->free_list);
 185         mempool_destroy(cl->objs_pool);
 186         kfree(cl);
 187 }
 188 EXPORT_SYMBOL(dm_mem_cache_client_destroy);
 189
 190 /*
 191  * Grow a clients cache by an amount of pages.
 192  *
 193  * Don't call from interrupt context!
 194  */
 195 int dm_mem_cache_grow(struct dm_mem_cache_client *cl, unsigned objects)
 196 {
 197         unsigned pages = objects * cl->chunks * cl->pages_per_chunk;
 198         struct page_list *pl, *last;
 199
 200         BUG_ON(!pages);
 201         pl = alloc_cache_pages(pages);
 202         if (!pl)
 203                 return -ENOMEM;
 204
 205         last = pl;
 206         while (last->next)
 207                 last = last->next;
 208
 209         spin_lock_irq(&cl->lock);
 210         last->next = cl->free_list;
 211         cl->free_list = pl;
 212         cl->free_pages += pages;
 213         cl->total_pages += pages;
 214         cl->objects += objects;
 215         spin_unlock_irq(&cl->lock);
 216
 217         mempool_resize(cl->objs_pool, cl->objects, GFP_NOIO);
 218         return 0;
 219 }
 220 EXPORT_SYMBOL(dm_mem_cache_grow);
 221
 222 /* Shrink a clients cache by an amount of pages */
 223 int dm_mem_cache_shrink(struct dm_mem_cache_client *cl, unsigned objects)
 224 {
 225         int r;
 226         unsigned pages = objects * cl->chunks * cl->pages_per_chunk, p = pages;
 227         unsigned long flags;
 228         struct page_list *last = NULL, *pl, *pos;
 229
 230         BUG_ON(!pages);
 231
 232         spin_lock_irqsave(&cl->lock, flags);
 233         pl = pos = cl->free_list;
 234         while (p-- && pos->next) {
 235                 last = pos;
 236                 pos = pos->next;
 237         }
 238
 239         if (++p)
 240                 r = -ENOMEM;
 241         else {
 242                 r = 0;
 243                 cl->free_list = pos;
 244                 cl->free_pages -= pages;
 245                 cl->total_pages -= pages;
 246                 cl->objects -= objects;
 247                 last->next = NULL;
 248         }
 249         spin_unlock_irqrestore(&cl->lock, flags);
 250
 251         if (!r) {
 252                 free_cache_pages(pl);
 253                 mempool_resize(cl->objs_pool, cl->objects, GFP_NOIO);
 254         }
 255
 256         return r;
 257 }
 258 EXPORT_SYMBOL(dm_mem_cache_shrink);
 259
 260 /*
 261  * Allocate/free a memory object
 262  *
 263  * Can be called from interrupt context
 264  */
 265 struct dm_mem_cache_object *dm_mem_cache_alloc(struct dm_mem_cache_client *cl)
 266 {
 267         int r = 0;
 268         unsigned pages = cl->chunks * cl->pages_per_chunk;
 269         unsigned long flags;
 270         struct dm_mem_cache_object *obj;
 271
 272         obj = mempool_alloc(cl->objs_pool, GFP_NOIO);
 273         if (!obj)
 274                 return ERR_PTR(-ENOMEM);
 275
 276         spin_lock_irqsave(&cl->lock, flags);
 277         if (pages > cl->free_pages)
 278                 r = -ENOMEM;
 279         else
 280                 cl->free_pages -= pages;
 281         spin_unlock_irqrestore(&cl->lock, flags);
 282
 283         if (r) {
 284                 mempool_free(obj, cl->objs_pool);
 285                 return ERR_PTR(r);
 286         }
 287
 288         alloc_chunks(cl, obj);
 289         return obj;
 290 }
 291 EXPORT_SYMBOL(dm_mem_cache_alloc);
 292
 293 void dm_mem_cache_free(struct dm_mem_cache_client *cl,
 294                        struct dm_mem_cache_object *obj)
 295 {
 296         free_chunks(cl, obj);
 297         mempool_free(obj, cl->objs_pool);
 298 }
 299 EXPORT_SYMBOL(dm_mem_cache_free);
 300
 301 MODULE_DESCRIPTION(DM_NAME " dm memory cache");
 302 MODULE_AUTHOR("Heinz Mauelshagen <heinzm@redhat.com>");
 303 MODULE_LICENSE("GPL");