mm/memcontrol.c

   1 /* memcontrol.c - Memory Controller
   2  *
   3  * Copyright IBM Corporation, 2007
   4  * Author Balbir Singh <balbir@linux.vnet.ibm.com>
   5  *
   6  * Copyright 2007 OpenVZ SWsoft Inc
   7  * Author: Pavel Emelianov <xemul@openvz.org>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  */
  19
  20 #include <linux/res_counter.h>
  21 #include <linux/memcontrol.h>
  22 #include <linux/cgroup.h>
  23 #include <linux/mm.h>
  24 #include <linux/page-flags.h>
  25 #include <linux/backing-dev.h>
  26 #include <linux/bit_spinlock.h>
  27 #include <linux/rcupdate.h>
  28 #include <linux/swap.h>
  29 #include <linux/spinlock.h>
  30 #include <linux/fs.h>
  31
  32 #include <asm/uaccess.h>
  33
  34 struct cgroup_subsys mem_cgroup_subsys;
  35 static const int MEM_CGROUP_RECLAIM_RETRIES = 5;
  36
  37 /*
  38  * The memory controller data structure. The memory controller controls both
  39  * page cache and RSS per cgroup. We would eventually like to provide
  40  * statistics based on the statistics developed by Rik Van Riel for clock-pro,
  41  * to help the administrator determine what knobs to tune.
  42  *
  43  * TODO: Add a water mark for the memory controller. Reclaim will begin when
  44  * we hit the water mark. May be even add a low water mark, such that
  45  * no reclaim occurs from a cgroup at it's low water mark, this is
  46  * a feature that will be implemented much later in the future.
  47  */
  48 struct mem_cgroup {
  49         struct cgroup_subsys_state css;
  50         /*
  51          * the counter to account for memory usage
  52          */
  53         struct res_counter res;
  54         /*
  55          * Per cgroup active and inactive list, similar to the
  56          * per zone LRU lists.
  57          * TODO: Consider making these lists per zone
  58          */
  59         struct list_head active_list;
  60         struct list_head inactive_list;
  61         /*
  62          * spin_lock to protect the per cgroup LRU
  63          */
  64         spinlock_t lru_lock;
  65         unsigned long control_type;     /* control RSS or RSS+Pagecache */
  66 };
  67
  68 /*
  69  * We use the lower bit of the page->page_cgroup pointer as a bit spin
  70  * lock. We need to ensure that page->page_cgroup is atleast two
  71  * byte aligned (based on comments from Nick Piggin)
  72  */
  73 #define PAGE_CGROUP_LOCK_BIT    0x0
  74 #define PAGE_CGROUP_LOCK                (1 << PAGE_CGROUP_LOCK_BIT)
  75
  76 /*
  77  * A page_cgroup page is associated with every page descriptor. The
  78  * page_cgroup helps us identify information about the cgroup
  79  */
  80 struct page_cgroup {
  81         struct list_head lru;           /* per cgroup LRU list */
  82         struct page *page;
  83         struct mem_cgroup *mem_cgroup;
  84         atomic_t ref_cnt;               /* Helpful when pages move b/w  */
  85                                         /* mapped and cached states     */
  86         int      flags;
  87 };
  88 #define PAGE_CGROUP_FLAG_CACHE  (0x1)   /* charged as cache */
  89
  90 enum {
  91         MEM_CGROUP_TYPE_UNSPEC = 0,
  92         MEM_CGROUP_TYPE_MAPPED,
  93         MEM_CGROUP_TYPE_CACHED,
  94         MEM_CGROUP_TYPE_ALL,
  95         MEM_CGROUP_TYPE_MAX,
  96 };
  97
  98 enum charge_type {
  99         MEM_CGROUP_CHARGE_TYPE_CACHE = 0,
 100         MEM_CGROUP_CHARGE_TYPE_MAPPED,
 101 };
 102
 103 static struct mem_cgroup init_mem_cgroup;
 104
 105 static inline
 106 struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont)
 107 {
 108         return container_of(cgroup_subsys_state(cont,
 109                                 mem_cgroup_subsys_id), struct mem_cgroup,
 110                                 css);
 111 }
 112
 113 static inline
 114 struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
 115 {
 116         return container_of(task_subsys_state(p, mem_cgroup_subsys_id),
 117                                 struct mem_cgroup, css);
 118 }
 119
 120 void mm_init_cgroup(struct mm_struct *mm, struct task_struct *p)
 121 {
 122         struct mem_cgroup *mem;
 123
 124         mem = mem_cgroup_from_task(p);
 125         css_get(&mem->css);
 126         mm->mem_cgroup = mem;
 127 }
 128
 129 void mm_free_cgroup(struct mm_struct *mm)
 130 {
 131         css_put(&mm->mem_cgroup->css);
 132 }
 133
 134 static inline int page_cgroup_locked(struct page *page)
 135 {
 136         return bit_spin_is_locked(PAGE_CGROUP_LOCK_BIT,
 137                                         &page->page_cgroup);
 138 }
 139
 140 void page_assign_page_cgroup(struct page *page, struct page_cgroup *pc)
 141 {
 142         int locked;
 143
 144         /*
 145          * While resetting the page_cgroup we might not hold the
 146          * page_cgroup lock. free_hot_cold_page() is an example
 147          * of such a scenario
 148          */
 149         if (pc)
 150                 VM_BUG_ON(!page_cgroup_locked(page));
 151         locked = (page->page_cgroup & PAGE_CGROUP_LOCK);
 152         page->page_cgroup = ((unsigned long)pc | locked);
 153 }
 154
 155 struct page_cgroup *page_get_page_cgroup(struct page *page)
 156 {
 157         return (struct page_cgroup *)
 158                 (page->page_cgroup & ~PAGE_CGROUP_LOCK);
 159 }
 160
 161 static void __always_inline lock_page_cgroup(struct page *page)
 162 {
 163         bit_spin_lock(PAGE_CGROUP_LOCK_BIT, &page->page_cgroup);
 164         VM_BUG_ON(!page_cgroup_locked(page));
 165 }
 166
 167 static void __always_inline unlock_page_cgroup(struct page *page)
 168 {
 169         bit_spin_unlock(PAGE_CGROUP_LOCK_BIT, &page->page_cgroup);
 170 }
 171
 172 /*
 173  * Tie new page_cgroup to struct page under lock_page_cgroup()
 174  * This can fail if the page has been tied to a page_cgroup.
 175  * If success, returns 0.
 176  */
 177 static inline int
 178 page_cgroup_assign_new_page_cgroup(struct page *page, struct page_cgroup *pc)
 179 {
 180         int ret = 0;
 181
 182         lock_page_cgroup(page);
 183         if (!page_get_page_cgroup(page))
 184                 page_assign_page_cgroup(page, pc);
 185         else /* A page is tied to other pc. */
 186                 ret = 1;
 187         unlock_page_cgroup(page);
 188         return ret;
 189 }
 190
 191 /*
 192  * Clear page->page_cgroup member under lock_page_cgroup().
 193  * If given "pc" value is different from one page->page_cgroup,
 194  * page->cgroup is not cleared.
 195  * Returns a value of page->page_cgroup at lock taken.
 196  * A can can detect failure of clearing by following
 197  *  clear_page_cgroup(page, pc) == pc
 198  */
 199
 200 static inline struct page_cgroup *
 201 clear_page_cgroup(struct page *page, struct page_cgroup *pc)
 202 {
 203         struct page_cgroup *ret;
 204         /* lock and clear */
 205         lock_page_cgroup(page);
 206         ret = page_get_page_cgroup(page);
 207         if (likely(ret == pc))
 208                 page_assign_page_cgroup(page, NULL);
 209         unlock_page_cgroup(page);
 210         return ret;
 211 }
 212
 213
 214 static void __mem_cgroup_move_lists(struct page_cgroup *pc, bool active)
 215 {
 216         if (active)
 217                 list_move(&pc->lru, &pc->mem_cgroup->active_list);
 218         else
 219                 list_move(&pc->lru, &pc->mem_cgroup->inactive_list);
 220 }
 221
 222 int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
 223 {
 224         int ret;
 225
 226         task_lock(task);
 227         ret = task->mm && mm_cgroup(task->mm) == mem;
 228         task_unlock(task);
 229         return ret;
 230 }
 231
 232 /*
 233  * This routine assumes that the appropriate zone's lru lock is already held
 234  */
 235 void mem_cgroup_move_lists(struct page_cgroup *pc, bool active)
 236 {
 237         struct mem_cgroup *mem;
 238         if (!pc)
 239                 return;
 240
 241         mem = pc->mem_cgroup;
 242
 243         spin_lock(&mem->lru_lock);
 244         __mem_cgroup_move_lists(pc, active);
 245         spin_unlock(&mem->lru_lock);
 246 }
 247
 248 unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
 249                                         struct list_head *dst,
 250                                         unsigned long *scanned, int order,
 251                                         int mode, struct zone *z,
 252                                         struct mem_cgroup *mem_cont,
 253                                         int active)
 254 {
 255         unsigned long nr_taken = 0;
 256         struct page *page;
 257         unsigned long scan;
 258         LIST_HEAD(pc_list);
 259         struct list_head *src;
 260         struct page_cgroup *pc, *tmp;
 261
 262         if (active)
 263                 src = &mem_cont->active_list;
 264         else
 265                 src = &mem_cont->inactive_list;
 266
 267         spin_lock(&mem_cont->lru_lock);
 268         scan = 0;
 269         list_for_each_entry_safe_reverse(pc, tmp, src, lru) {
 270                 if (scan >= nr_to_scan)
 271                         break;
 272                 page = pc->page;
 273                 VM_BUG_ON(!pc);
 274
 275                 if (unlikely(!PageLRU(page)))
 276                         continue;
 277
 278                 if (PageActive(page) && !active) {
 279                         __mem_cgroup_move_lists(pc, true);
 280                         continue;
 281                 }
 282                 if (!PageActive(page) && active) {
 283                         __mem_cgroup_move_lists(pc, false);
 284                         continue;
 285                 }
 286
 287                 /*
 288                  * Reclaim, per zone
 289                  * TODO: make the active/inactive lists per zone
 290                  */
 291                 if (page_zone(page) != z)
 292                         continue;
 293
 294                 scan++;
 295                 list_move(&pc->lru, &pc_list);
 296
 297                 if (__isolate_lru_page(page, mode) == 0) {
 298                         list_move(&page->lru, dst);
 299                         nr_taken++;
 300                 }
 301         }
 302
 303         list_splice(&pc_list, src);
 304         spin_unlock(&mem_cont->lru_lock);
 305
 306         *scanned = scan;
 307         return nr_taken;
 308 }
 309
 310 /*
 311  * Charge the memory controller for page usage.
 312  * Return
 313  * 0 if the charge was successful
 314  * < 0 if the cgroup is over its limit
 315  */
 316 static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
 317                                 gfp_t gfp_mask, enum charge_type ctype)
 318 {
 319         struct mem_cgroup *mem;
 320         struct page_cgroup *pc;
 321         unsigned long flags;
 322         unsigned long nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
 323
 324         /*
 325          * Should page_cgroup's go to their own slab?
 326          * One could optimize the performance of the charging routine
 327          * by saving a bit in the page_flags and using it as a lock
 328          * to see if the cgroup page already has a page_cgroup associated
 329          * with it
 330          */
 331 retry:
 332         lock_page_cgroup(page);
 333         pc = page_get_page_cgroup(page);
 334         /*
 335          * The page_cgroup exists and the page has already been accounted
 336          */
 337         if (pc) {
 338                 if (unlikely(!atomic_inc_not_zero(&pc->ref_cnt))) {
 339                         /* this page is under being uncharged ? */
 340                         unlock_page_cgroup(page);
 341                         cpu_relax();
 342                         goto retry;
 343                 } else {
 344                         unlock_page_cgroup(page);
 345                         goto done;
 346                 }
 347         }
 348         unlock_page_cgroup(page);
 349
 350         pc = kzalloc(sizeof(struct page_cgroup), gfp_mask);
 351         if (pc == NULL)
 352                 goto err;
 353
 354         /*
 355          * We always charge the cgroup the mm_struct belongs to.
 356          * The mm_struct's mem_cgroup changes on task migration if the
 357          * thread group leader migrates. It's possible that mm is not
 358          * set, if so charge the init_mm (happens for pagecache usage).
 359          */
 360         if (!mm)
 361                 mm = &init_mm;
 362
 363         rcu_read_lock();
 364         mem = rcu_dereference(mm->mem_cgroup);
 365         /*
 366          * For every charge from the cgroup, increment reference
 367          * count
 368          */
 369         css_get(&mem->css);
 370         rcu_read_unlock();
 371
 372         /*
 373          * If we created the page_cgroup, we should free it on exceeding
 374          * the cgroup limit.
 375          */
 376         while (res_counter_charge(&mem->res, PAGE_SIZE)) {
 377                 if (!(gfp_mask & __GFP_WAIT))
 378                         goto out;
 379
 380                 if (try_to_free_mem_cgroup_pages(mem, gfp_mask))
 381                         continue;
 382
 383                 /*
 384                  * try_to_free_mem_cgroup_pages() might not give us a full
 385                  * picture of reclaim. Some pages are reclaimed and might be
 386                  * moved to swap cache or just unmapped from the cgroup.
 387                  * Check the limit again to see if the reclaim reduced the
 388                  * current usage of the cgroup before giving up
 389                  */
 390                 if (res_counter_check_under_limit(&mem->res))
 391                         continue;
 392
 393                 if (!nr_retries--) {
 394                         mem_cgroup_out_of_memory(mem, gfp_mask);
 395                         goto out;
 396                 }
 397                 congestion_wait(WRITE, HZ/10);
 398         }
 399
 400         atomic_set(&pc->ref_cnt, 1);
 401         pc->mem_cgroup = mem;
 402         pc->page = page;
 403         pc->flags = 0;
 404         if (ctype == MEM_CGROUP_CHARGE_TYPE_CACHE)
 405                 pc->flags |= PAGE_CGROUP_FLAG_CACHE;
 406
 407         if (page_cgroup_assign_new_page_cgroup(page, pc)) {
 408                 /*
 409                  * Another charge has been added to this page already.
 410                  * We take lock_page_cgroup(page) again and read
 411                  * page->cgroup, increment refcnt.... just retry is OK.
 412                  */
 413                 res_counter_uncharge(&mem->res, PAGE_SIZE);
 414                 css_put(&mem->css);
 415                 kfree(pc);
 416                 goto retry;
 417         }
 418
 419         spin_lock_irqsave(&mem->lru_lock, flags);
 420         list_add(&pc->lru, &mem->active_list);
 421         spin_unlock_irqrestore(&mem->lru_lock, flags);
 422
 423 done:
 424         return 0;
 425 out:
 426         css_put(&mem->css);
 427         kfree(pc);
 428 err:
 429         return -ENOMEM;
 430 }
 431
 432 int mem_cgroup_charge(struct page *page, struct mm_struct *mm,
 433                         gfp_t gfp_mask)
 434 {
 435         return mem_cgroup_charge_common(page, mm, gfp_mask,
 436                         MEM_CGROUP_CHARGE_TYPE_MAPPED);
 437 }
 438
 439 /*
 440  * See if the cached pages should be charged at all?
 441  */
 442 int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
 443                                 gfp_t gfp_mask)
 444 {
 445         int ret = 0;
 446         struct mem_cgroup *mem;
 447         if (!mm)
 448                 mm = &init_mm;
 449
 450         rcu_read_lock();
 451         mem = rcu_dereference(mm->mem_cgroup);
 452         css_get(&mem->css);
 453         rcu_read_unlock();
 454         if (mem->control_type == MEM_CGROUP_TYPE_ALL)
 455                 ret = mem_cgroup_charge_common(page, mm, gfp_mask,
 456                                 MEM_CGROUP_CHARGE_TYPE_CACHE);
 457         css_put(&mem->css);
 458         return ret;
 459 }
 460
 461 /*
 462  * Uncharging is always a welcome operation, we never complain, simply
 463  * uncharge.
 464  */
 465 void mem_cgroup_uncharge(struct page_cgroup *pc)
 466 {
 467         struct mem_cgroup *mem;
 468         struct page *page;
 469         unsigned long flags;
 470
 471         /*
 472          * This can handle cases when a page is not charged at all and we
 473          * are switching between handling the control_type.
 474          */
 475         if (!pc)
 476                 return;
 477
 478         if (atomic_dec_and_test(&pc->ref_cnt)) {
 479                 page = pc->page;
 480                 /*
 481                  * get page->cgroup and clear it under lock.
 482                  * force_empty can drop page->cgroup without checking refcnt.
 483                  */
 484                 if (clear_page_cgroup(page, pc) == pc) {
 485                         mem = pc->mem_cgroup;
 486                         css_put(&mem->css);
 487                         res_counter_uncharge(&mem->res, PAGE_SIZE);
 488                         spin_lock_irqsave(&mem->lru_lock, flags);
 489                         list_del_init(&pc->lru);
 490                         spin_unlock_irqrestore(&mem->lru_lock, flags);
 491                         kfree(pc);
 492                 }
 493         }
 494 }
 495 /*
 496  * Returns non-zero if a page (under migration) has valid page_cgroup member.
 497  * Refcnt of page_cgroup is incremented.
 498  */
 499
 500 int mem_cgroup_prepare_migration(struct page *page)
 501 {
 502         struct page_cgroup *pc;
 503         int ret = 0;
 504         lock_page_cgroup(page);
 505         pc = page_get_page_cgroup(page);
 506         if (pc && atomic_inc_not_zero(&pc->ref_cnt))
 507                 ret = 1;
 508         unlock_page_cgroup(page);
 509         return ret;
 510 }
 511
 512 void mem_cgroup_end_migration(struct page *page)
 513 {
 514         struct page_cgroup *pc = page_get_page_cgroup(page);
 515         mem_cgroup_uncharge(pc);
 516 }
 517 /*
 518  * We know both *page* and *newpage* are now not-on-LRU and Pg_locked.
 519  * And no race with uncharge() routines because page_cgroup for *page*
 520  * has extra one reference by mem_cgroup_prepare_migration.
 521  */
 522
 523 void mem_cgroup_page_migration(struct page *page, struct page *newpage)
 524 {
 525         struct page_cgroup *pc;
 526 retry:
 527         pc = page_get_page_cgroup(page);
 528         if (!pc)
 529                 return;
 530         if (clear_page_cgroup(page, pc) != pc)
 531                 goto retry;
 532         pc->page = newpage;
 533         lock_page_cgroup(newpage);
 534         page_assign_page_cgroup(newpage, pc);
 535         unlock_page_cgroup(newpage);
 536         return;
 537 }
 538
 539 /*
 540  * This routine traverse page_cgroup in given list and drop them all.
 541  * This routine ignores page_cgroup->ref_cnt.
 542  * *And* this routine doesn't reclaim page itself, just removes page_cgroup.
 543  */
 544 #define FORCE_UNCHARGE_BATCH    (128)
 545 static void
 546 mem_cgroup_force_empty_list(struct mem_cgroup *mem, struct list_head *list)
 547 {
 548         struct page_cgroup *pc;
 549         struct page *page;
 550         int count;
 551         unsigned long flags;
 552
 553 retry:
 554         count = FORCE_UNCHARGE_BATCH;
 555         spin_lock_irqsave(&mem->lru_lock, flags);
 556
 557         while (--count && !list_empty(list)) {
 558                 pc = list_entry(list->prev, struct page_cgroup, lru);
 559                 page = pc->page;
 560                 /* Avoid race with charge */
 561                 atomic_set(&pc->ref_cnt, 0);
 562                 if (clear_page_cgroup(page, pc) == pc) {
 563                         css_put(&mem->css);
 564                         res_counter_uncharge(&mem->res, PAGE_SIZE);
 565                         list_del_init(&pc->lru);
 566                         kfree(pc);
 567                 } else  /* being uncharged ? ...do relax */
 568                         break;
 569         }
 570         spin_unlock_irqrestore(&mem->lru_lock, flags);
 571         if (!list_empty(list)) {
 572                 cond_resched();
 573                 goto retry;
 574         }
 575         return;
 576 }
 577
 578 /*
 579  * make mem_cgroup's charge to be 0 if there is no task.
 580  * This enables deleting this mem_cgroup.
 581  */
 582
 583 int mem_cgroup_force_empty(struct mem_cgroup *mem)
 584 {
 585         int ret = -EBUSY;
 586         css_get(&mem->css);
 587         /*
 588          * page reclaim code (kswapd etc..) will move pages between
 589 `        * active_list <-> inactive_list while we don't take a lock.
 590          * So, we have to do loop here until all lists are empty.
 591          */
 592         while (!(list_empty(&mem->active_list) &&
 593                  list_empty(&mem->inactive_list))) {
 594                 if (atomic_read(&mem->css.cgroup->count) > 0)
 595                         goto out;
 596                 /* drop all page_cgroup in active_list */
 597                 mem_cgroup_force_empty_list(mem, &mem->active_list);
 598                 /* drop all page_cgroup in inactive_list */
 599                 mem_cgroup_force_empty_list(mem, &mem->inactive_list);
 600         }
 601         ret = 0;
 602 out:
 603         css_put(&mem->css);
 604         return ret;
 605 }
 606
 607
 608
 609 int mem_cgroup_write_strategy(char *buf, unsigned long long *tmp)
 610 {
 611         *tmp = memparse(buf, &buf);
 612         if (*buf != '\0')
 613                 return -EINVAL;
 614
 615         /*
 616          * Round up the value to the closest page size
 617          */
 618         *tmp = ((*tmp + PAGE_SIZE - 1) >> PAGE_SHIFT) << PAGE_SHIFT;
 619         return 0;
 620 }
 621
 622 static ssize_t mem_cgroup_read(struct cgroup *cont,
 623                         struct cftype *cft, struct file *file,
 624                         char __user *userbuf, size_t nbytes, loff_t *ppos)
 625 {
 626         return res_counter_read(&mem_cgroup_from_cont(cont)->res,
 627                                 cft->private, userbuf, nbytes, ppos,
 628                                 NULL);
 629 }
 630
 631 static ssize_t mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
 632                                 struct file *file, const char __user *userbuf,
 633                                 size_t nbytes, loff_t *ppos)
 634 {
 635         return res_counter_write(&mem_cgroup_from_cont(cont)->res,
 636                                 cft->private, userbuf, nbytes, ppos,
 637                                 mem_cgroup_write_strategy);
 638 }
 639
 640 static ssize_t mem_control_type_write(struct cgroup *cont,
 641                         struct cftype *cft, struct file *file,
 642                         const char __user *userbuf,
 643                         size_t nbytes, loff_t *pos)
 644 {
 645         int ret;
 646         char *buf, *end;
 647         unsigned long tmp;
 648         struct mem_cgroup *mem;
 649
 650         mem = mem_cgroup_from_cont(cont);
 651         buf = kmalloc(nbytes + 1, GFP_KERNEL);
 652         ret = -ENOMEM;
 653         if (buf == NULL)
 654                 goto out;
 655
 656         buf[nbytes] = 0;
 657         ret = -EFAULT;
 658         if (copy_from_user(buf, userbuf, nbytes))
 659                 goto out_free;
 660
 661         ret = -EINVAL;
 662         tmp = simple_strtoul(buf, &end, 10);
 663         if (*end != '\0')
 664                 goto out_free;
 665
 666         if (tmp <= MEM_CGROUP_TYPE_UNSPEC || tmp >= MEM_CGROUP_TYPE_MAX)
 667                 goto out_free;
 668
 669         mem->control_type = tmp;
 670         ret = nbytes;
 671 out_free:
 672         kfree(buf);
 673 out:
 674         return ret;
 675 }
 676
 677 static ssize_t mem_control_type_read(struct cgroup *cont,
 678                                 struct cftype *cft,
 679                                 struct file *file, char __user *userbuf,
 680                                 size_t nbytes, loff_t *ppos)
 681 {
 682         unsigned long val;
 683         char buf[64], *s;
 684         struct mem_cgroup *mem;
 685
 686         mem = mem_cgroup_from_cont(cont);
 687         s = buf;
 688         val = mem->control_type;
 689         s += sprintf(s, "%lu\n", val);
 690         return simple_read_from_buffer((void __user *)userbuf, nbytes,
 691                         ppos, buf, s - buf);
 692 }
 693
 694
 695 static ssize_t mem_force_empty_write(struct cgroup *cont,
 696                                 struct cftype *cft, struct file *file,
 697                                 const char __user *userbuf,
 698                                 size_t nbytes, loff_t *ppos)
 699 {
 700         struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
 701         int ret;
 702         ret = mem_cgroup_force_empty(mem);
 703         if (!ret)
 704                 ret = nbytes;
 705         return ret;
 706 }
 707
 708 /*
 709  * Note: This should be removed if cgroup supports write-only file.
 710  */
 711
 712 static ssize_t mem_force_empty_read(struct cgroup *cont,
 713                                 struct cftype *cft,
 714                                 struct file *file, char __user *userbuf,
 715                                 size_t nbytes, loff_t *ppos)
 716 {
 717         return -EINVAL;
 718 }
 719
 720
 721 static struct cftype mem_cgroup_files[] = {
 722         {
 723                 .name = "usage_in_bytes",
 724                 .private = RES_USAGE,
 725                 .read = mem_cgroup_read,
 726         },
 727         {
 728                 .name = "limit_in_bytes",
 729                 .private = RES_LIMIT,
 730                 .write = mem_cgroup_write,
 731                 .read = mem_cgroup_read,
 732         },
 733         {
 734                 .name = "failcnt",
 735                 .private = RES_FAILCNT,
 736                 .read = mem_cgroup_read,
 737         },
 738         {
 739                 .name = "control_type",
 740                 .write = mem_control_type_write,
 741                 .read = mem_control_type_read,
 742         },
 743         {
 744                 .name = "force_empty",
 745                 .write = mem_force_empty_write,
 746                 .read = mem_force_empty_read,
 747         },
 748 };
 749
 750 static struct mem_cgroup init_mem_cgroup;
 751
 752 static struct cgroup_subsys_state *
 753 mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
 754 {
 755         struct mem_cgroup *mem;
 756
 757         if (unlikely((cont->parent) == NULL)) {
 758                 mem = &init_mem_cgroup;
 759                 init_mm.mem_cgroup = mem;
 760         } else
 761                 mem = kzalloc(sizeof(struct mem_cgroup), GFP_KERNEL);
 762
 763         if (mem == NULL)
 764                 return NULL;
 765
 766         res_counter_init(&mem->res);
 767         INIT_LIST_HEAD(&mem->active_list);
 768         INIT_LIST_HEAD(&mem->inactive_list);
 769         spin_lock_init(&mem->lru_lock);
 770         mem->control_type = MEM_CGROUP_TYPE_ALL;
 771         return &mem->css;
 772 }
 773
 774 static void mem_cgroup_destroy(struct cgroup_subsys *ss,
 775                                 struct cgroup *cont)
 776 {
 777         kfree(mem_cgroup_from_cont(cont));
 778 }
 779
 780 static int mem_cgroup_populate(struct cgroup_subsys *ss,
 781                                 struct cgroup *cont)
 782 {
 783         return cgroup_add_files(cont, ss, mem_cgroup_files,
 784                                         ARRAY_SIZE(mem_cgroup_files));
 785 }
 786
 787 static void mem_cgroup_move_task(struct cgroup_subsys *ss,
 788                                 struct cgroup *cont,
 789                                 struct cgroup *old_cont,
 790                                 struct task_struct *p)
 791 {
 792         struct mm_struct *mm;
 793         struct mem_cgroup *mem, *old_mem;
 794
 795         mm = get_task_mm(p);
 796         if (mm == NULL)
 797                 return;
 798
 799         mem = mem_cgroup_from_cont(cont);
 800         old_mem = mem_cgroup_from_cont(old_cont);
 801
 802         if (mem == old_mem)
 803                 goto out;
 804
 805         /*
 806          * Only thread group leaders are allowed to migrate, the mm_struct is
 807          * in effect owned by the leader
 808          */
 809         if (p->tgid != p->pid)
 810                 goto out;
 811
 812         css_get(&mem->css);
 813         rcu_assign_pointer(mm->mem_cgroup, mem);
 814         css_put(&old_mem->css);
 815
 816 out:
 817         mmput(mm);
 818         return;
 819 }
 820
 821 struct cgroup_subsys mem_cgroup_subsys = {
 822         .name = "memory",
 823         .subsys_id = mem_cgroup_subsys_id,
 824         .create = mem_cgroup_create,
 825         .destroy = mem_cgroup_destroy,
 826         .populate = mem_cgroup_populate,
 827         .attach = mem_cgroup_move_task,
 828         .early_init = 1,
 829 };