| 1 | /* |
| 2 | * Generic pidhash and scalable, time-bounded PID allocator |
| 3 | * |
| 4 | * (C) 2002-2003 Nadia Yvette Chambers, IBM |
| 5 | * (C) 2004 Nadia Yvette Chambers, Oracle |
| 6 | * (C) 2002-2004 Ingo Molnar, Red Hat |
| 7 | * |
| 8 | * pid-structures are backing objects for tasks sharing a given ID to chain |
| 9 | * against. There is very little to them aside from hashing them and |
| 10 | * parking tasks using given ID's on a list. |
| 11 | * |
| 12 | * The hash is always changed with the tasklist_lock write-acquired, |
| 13 | * and the hash is only accessed with the tasklist_lock at least |
| 14 | * read-acquired, so there's no additional SMP locking needed here. |
| 15 | * |
| 16 | * We have a list of bitmap pages, which bitmaps represent the PID space. |
| 17 | * Allocating and freeing PIDs is completely lockless. The worst-case |
| 18 | * allocation scenario when all but one out of 1 million PIDs possible are |
| 19 | * allocated already: the scanning of 32 list entries and at most PAGE_SIZE |
| 20 | * bytes. The typical fastpath is a single successful setbit. Freeing is O(1). |
| 21 | * |
| 22 | * Pid namespaces: |
| 23 | * (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc. |
| 24 | * (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM |
| 25 | * Many thanks to Oleg Nesterov for comments and help |
| 26 | * |
| 27 | */ |
| 28 | |
| 29 | #include <linux/mm.h> |
| 30 | #include <linux/export.h> |
| 31 | #include <linux/slab.h> |
| 32 | #include <linux/init.h> |
| 33 | #include <linux/rculist.h> |
| 34 | #include <linux/bootmem.h> |
| 35 | #include <linux/hash.h> |
| 36 | #include <linux/pid_namespace.h> |
| 37 | #include <linux/init_task.h> |
| 38 | #include <linux/syscalls.h> |
| 39 | #include <linux/proc_ns.h> |
| 40 | #include <linux/proc_fs.h> |
| 41 | |
| 42 | #define pid_hashfn(nr, ns) \ |
| 43 | hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift) |
| 44 | static struct hlist_head *pid_hash; |
| 45 | static unsigned int pidhash_shift = 4; |
| 46 | struct pid init_struct_pid = INIT_STRUCT_PID; |
| 47 | |
| 48 | int pid_max = PID_MAX_DEFAULT; |
| 49 | |
| 50 | #define RESERVED_PIDS 300 |
| 51 | |
| 52 | int pid_max_min = RESERVED_PIDS + 1; |
| 53 | int pid_max_max = PID_MAX_LIMIT; |
| 54 | |
| 55 | static inline int mk_pid(struct pid_namespace *pid_ns, |
| 56 | struct pidmap *map, int off) |
| 57 | { |
| 58 | return (map - pid_ns->pidmap)*BITS_PER_PAGE + off; |
| 59 | } |
| 60 | |
| 61 | #define find_next_offset(map, off) \ |
| 62 | find_next_zero_bit((map)->page, BITS_PER_PAGE, off) |
| 63 | |
| 64 | /* |
| 65 | * PID-map pages start out as NULL, they get allocated upon |
| 66 | * first use and are never deallocated. This way a low pid_max |
| 67 | * value does not cause lots of bitmaps to be allocated, but |
| 68 | * the scheme scales to up to 4 million PIDs, runtime. |
| 69 | */ |
| 70 | struct pid_namespace init_pid_ns = { |
| 71 | .kref = { |
| 72 | .refcount = ATOMIC_INIT(2), |
| 73 | }, |
| 74 | .pidmap = { |
| 75 | [ 0 ... PIDMAP_ENTRIES-1] = { ATOMIC_INIT(BITS_PER_PAGE), NULL } |
| 76 | }, |
| 77 | .last_pid = 0, |
| 78 | .level = 0, |
| 79 | .child_reaper = &init_task, |
| 80 | .user_ns = &init_user_ns, |
| 81 | .proc_inum = PROC_PID_INIT_INO, |
| 82 | }; |
| 83 | EXPORT_SYMBOL_GPL(init_pid_ns); |
| 84 | |
| 85 | /* |
| 86 | * Note: disable interrupts while the pidmap_lock is held as an |
| 87 | * interrupt might come in and do read_lock(&tasklist_lock). |
| 88 | * |
| 89 | * If we don't disable interrupts there is a nasty deadlock between |
| 90 | * detach_pid()->free_pid() and another cpu that does |
| 91 | * spin_lock(&pidmap_lock) followed by an interrupt routine that does |
| 92 | * read_lock(&tasklist_lock); |
| 93 | * |
| 94 | * After we clean up the tasklist_lock and know there are no |
| 95 | * irq handlers that take it we can leave the interrupts enabled. |
| 96 | * For now it is easier to be safe than to prove it can't happen. |
| 97 | */ |
| 98 | |
| 99 | static __cacheline_aligned_in_smp DEFINE_SPINLOCK(pidmap_lock); |
| 100 | |
| 101 | static void free_pidmap(struct upid *upid) |
| 102 | { |
| 103 | int nr = upid->nr; |
| 104 | struct pidmap *map = upid->ns->pidmap + nr / BITS_PER_PAGE; |
| 105 | int offset = nr & BITS_PER_PAGE_MASK; |
| 106 | |
| 107 | clear_bit(offset, map->page); |
| 108 | atomic_inc(&map->nr_free); |
| 109 | } |
| 110 | |
| 111 | /* |
| 112 | * If we started walking pids at 'base', is 'a' seen before 'b'? |
| 113 | */ |
| 114 | static int pid_before(int base, int a, int b) |
| 115 | { |
| 116 | /* |
| 117 | * This is the same as saying |
| 118 | * |
| 119 | * (a - base + MAXUINT) % MAXUINT < (b - base + MAXUINT) % MAXUINT |
| 120 | * and that mapping orders 'a' and 'b' with respect to 'base'. |
| 121 | */ |
| 122 | return (unsigned)(a - base) < (unsigned)(b - base); |
| 123 | } |
| 124 | |
| 125 | /* |
| 126 | * We might be racing with someone else trying to set pid_ns->last_pid |
| 127 | * at the pid allocation time (there's also a sysctl for this, but racing |
| 128 | * with this one is OK, see comment in kernel/pid_namespace.c about it). |
| 129 | * We want the winner to have the "later" value, because if the |
| 130 | * "earlier" value prevails, then a pid may get reused immediately. |
| 131 | * |
| 132 | * Since pids rollover, it is not sufficient to just pick the bigger |
| 133 | * value. We have to consider where we started counting from. |
| 134 | * |
| 135 | * 'base' is the value of pid_ns->last_pid that we observed when |
| 136 | * we started looking for a pid. |
| 137 | * |
| 138 | * 'pid' is the pid that we eventually found. |
| 139 | */ |
| 140 | static void set_last_pid(struct pid_namespace *pid_ns, int base, int pid) |
| 141 | { |
| 142 | int prev; |
| 143 | int last_write = base; |
| 144 | do { |
| 145 | prev = last_write; |
| 146 | last_write = cmpxchg(&pid_ns->last_pid, prev, pid); |
| 147 | } while ((prev != last_write) && (pid_before(base, last_write, pid))); |
| 148 | } |
| 149 | |
| 150 | static int alloc_pidmap(struct pid_namespace *pid_ns) |
| 151 | { |
| 152 | int i, offset, max_scan, pid, last = pid_ns->last_pid; |
| 153 | struct pidmap *map; |
| 154 | |
| 155 | pid = last + 1; |
| 156 | if (pid >= pid_max) |
| 157 | pid = RESERVED_PIDS; |
| 158 | offset = pid & BITS_PER_PAGE_MASK; |
| 159 | map = &pid_ns->pidmap[pid/BITS_PER_PAGE]; |
| 160 | /* |
| 161 | * If last_pid points into the middle of the map->page we |
| 162 | * want to scan this bitmap block twice, the second time |
| 163 | * we start with offset == 0 (or RESERVED_PIDS). |
| 164 | */ |
| 165 | max_scan = DIV_ROUND_UP(pid_max, BITS_PER_PAGE) - !offset; |
| 166 | for (i = 0; i <= max_scan; ++i) { |
| 167 | if (unlikely(!map->page)) { |
| 168 | void *page = kzalloc(PAGE_SIZE, GFP_KERNEL); |
| 169 | /* |
| 170 | * Free the page if someone raced with us |
| 171 | * installing it: |
| 172 | */ |
| 173 | spin_lock_irq(&pidmap_lock); |
| 174 | if (!map->page) { |
| 175 | map->page = page; |
| 176 | page = NULL; |
| 177 | } |
| 178 | spin_unlock_irq(&pidmap_lock); |
| 179 | kfree(page); |
| 180 | if (unlikely(!map->page)) |
| 181 | break; |
| 182 | } |
| 183 | if (likely(atomic_read(&map->nr_free))) { |
| 184 | for ( ; ; ) { |
| 185 | if (!test_and_set_bit(offset, map->page)) { |
| 186 | atomic_dec(&map->nr_free); |
| 187 | set_last_pid(pid_ns, last, pid); |
| 188 | return pid; |
| 189 | } |
| 190 | offset = find_next_offset(map, offset); |
| 191 | if (offset >= BITS_PER_PAGE) |
| 192 | break; |
| 193 | pid = mk_pid(pid_ns, map, offset); |
| 194 | if (pid >= pid_max) |
| 195 | break; |
| 196 | } |
| 197 | } |
| 198 | if (map < &pid_ns->pidmap[(pid_max-1)/BITS_PER_PAGE]) { |
| 199 | ++map; |
| 200 | offset = 0; |
| 201 | } else { |
| 202 | map = &pid_ns->pidmap[0]; |
| 203 | offset = RESERVED_PIDS; |
| 204 | if (unlikely(last == offset)) |
| 205 | break; |
| 206 | } |
| 207 | pid = mk_pid(pid_ns, map, offset); |
| 208 | } |
| 209 | return -1; |
| 210 | } |
| 211 | |
| 212 | int next_pidmap(struct pid_namespace *pid_ns, unsigned int last) |
| 213 | { |
| 214 | int offset; |
| 215 | struct pidmap *map, *end; |
| 216 | |
| 217 | if (last >= PID_MAX_LIMIT) |
| 218 | return -1; |
| 219 | |
| 220 | offset = (last + 1) & BITS_PER_PAGE_MASK; |
| 221 | map = &pid_ns->pidmap[(last + 1)/BITS_PER_PAGE]; |
| 222 | end = &pid_ns->pidmap[PIDMAP_ENTRIES]; |
| 223 | for (; map < end; map++, offset = 0) { |
| 224 | if (unlikely(!map->page)) |
| 225 | continue; |
| 226 | offset = find_next_bit((map)->page, BITS_PER_PAGE, offset); |
| 227 | if (offset < BITS_PER_PAGE) |
| 228 | return mk_pid(pid_ns, map, offset); |
| 229 | } |
| 230 | return -1; |
| 231 | } |
| 232 | |
| 233 | void put_pid(struct pid *pid) |
| 234 | { |
| 235 | struct pid_namespace *ns; |
| 236 | |
| 237 | if (!pid) |
| 238 | return; |
| 239 | |
| 240 | ns = pid->numbers[pid->level].ns; |
| 241 | if ((atomic_read(&pid->count) == 1) || |
| 242 | atomic_dec_and_test(&pid->count)) { |
| 243 | kmem_cache_free(ns->pid_cachep, pid); |
| 244 | put_pid_ns(ns); |
| 245 | } |
| 246 | } |
| 247 | EXPORT_SYMBOL_GPL(put_pid); |
| 248 | |
| 249 | static void delayed_put_pid(struct rcu_head *rhp) |
| 250 | { |
| 251 | struct pid *pid = container_of(rhp, struct pid, rcu); |
| 252 | put_pid(pid); |
| 253 | } |
| 254 | |
| 255 | void free_pid(struct pid *pid) |
| 256 | { |
| 257 | /* We can be called with write_lock_irq(&tasklist_lock) held */ |
| 258 | int i; |
| 259 | unsigned long flags; |
| 260 | |
| 261 | spin_lock_irqsave(&pidmap_lock, flags); |
| 262 | for (i = 0; i <= pid->level; i++) { |
| 263 | struct upid *upid = pid->numbers + i; |
| 264 | struct pid_namespace *ns = upid->ns; |
| 265 | hlist_del_rcu(&upid->pid_chain); |
| 266 | switch(--ns->nr_hashed) { |
| 267 | case 2: |
| 268 | case 1: |
| 269 | /* When all that is left in the pid namespace |
| 270 | * is the reaper wake up the reaper. The reaper |
| 271 | * may be sleeping in zap_pid_ns_processes(). |
| 272 | */ |
| 273 | wake_up_process(ns->child_reaper); |
| 274 | break; |
| 275 | case 0: |
| 276 | schedule_work(&ns->proc_work); |
| 277 | break; |
| 278 | } |
| 279 | } |
| 280 | spin_unlock_irqrestore(&pidmap_lock, flags); |
| 281 | |
| 282 | for (i = 0; i <= pid->level; i++) |
| 283 | free_pidmap(pid->numbers + i); |
| 284 | |
| 285 | call_rcu(&pid->rcu, delayed_put_pid); |
| 286 | } |
| 287 | |
| 288 | struct pid *alloc_pid(struct pid_namespace *ns) |
| 289 | { |
| 290 | struct pid *pid; |
| 291 | enum pid_type type; |
| 292 | int i, nr; |
| 293 | struct pid_namespace *tmp; |
| 294 | struct upid *upid; |
| 295 | |
| 296 | pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL); |
| 297 | if (!pid) |
| 298 | goto out; |
| 299 | |
| 300 | tmp = ns; |
| 301 | pid->level = ns->level; |
| 302 | for (i = ns->level; i >= 0; i--) { |
| 303 | nr = alloc_pidmap(tmp); |
| 304 | if (nr < 0) |
| 305 | goto out_free; |
| 306 | |
| 307 | pid->numbers[i].nr = nr; |
| 308 | pid->numbers[i].ns = tmp; |
| 309 | tmp = tmp->parent; |
| 310 | } |
| 311 | |
| 312 | if (unlikely(is_child_reaper(pid))) { |
| 313 | if (pid_ns_prepare_proc(ns)) |
| 314 | goto out_free; |
| 315 | } |
| 316 | |
| 317 | get_pid_ns(ns); |
| 318 | atomic_set(&pid->count, 1); |
| 319 | for (type = 0; type < PIDTYPE_MAX; ++type) |
| 320 | INIT_HLIST_HEAD(&pid->tasks[type]); |
| 321 | |
| 322 | upid = pid->numbers + ns->level; |
| 323 | spin_lock_irq(&pidmap_lock); |
| 324 | if (!(ns->nr_hashed & PIDNS_HASH_ADDING)) |
| 325 | goto out_unlock; |
| 326 | for ( ; upid >= pid->numbers; --upid) { |
| 327 | hlist_add_head_rcu(&upid->pid_chain, |
| 328 | &pid_hash[pid_hashfn(upid->nr, upid->ns)]); |
| 329 | upid->ns->nr_hashed++; |
| 330 | } |
| 331 | spin_unlock_irq(&pidmap_lock); |
| 332 | |
| 333 | out: |
| 334 | return pid; |
| 335 | |
| 336 | out_unlock: |
| 337 | spin_unlock_irq(&pidmap_lock); |
| 338 | put_pid_ns(ns); |
| 339 | |
| 340 | out_free: |
| 341 | while (++i <= ns->level) |
| 342 | free_pidmap(pid->numbers + i); |
| 343 | |
| 344 | kmem_cache_free(ns->pid_cachep, pid); |
| 345 | pid = NULL; |
| 346 | goto out; |
| 347 | } |
| 348 | |
| 349 | void disable_pid_allocation(struct pid_namespace *ns) |
| 350 | { |
| 351 | spin_lock_irq(&pidmap_lock); |
| 352 | ns->nr_hashed &= ~PIDNS_HASH_ADDING; |
| 353 | spin_unlock_irq(&pidmap_lock); |
| 354 | } |
| 355 | |
| 356 | struct pid *find_pid_ns(int nr, struct pid_namespace *ns) |
| 357 | { |
| 358 | struct upid *pnr; |
| 359 | |
| 360 | hlist_for_each_entry_rcu(pnr, |
| 361 | &pid_hash[pid_hashfn(nr, ns)], pid_chain) |
| 362 | if (pnr->nr == nr && pnr->ns == ns) |
| 363 | return container_of(pnr, struct pid, |
| 364 | numbers[ns->level]); |
| 365 | |
| 366 | return NULL; |
| 367 | } |
| 368 | EXPORT_SYMBOL_GPL(find_pid_ns); |
| 369 | |
| 370 | struct pid *find_vpid(int nr) |
| 371 | { |
| 372 | return find_pid_ns(nr, task_active_pid_ns(current)); |
| 373 | } |
| 374 | EXPORT_SYMBOL_GPL(find_vpid); |
| 375 | |
| 376 | /* |
| 377 | * attach_pid() must be called with the tasklist_lock write-held. |
| 378 | */ |
| 379 | void attach_pid(struct task_struct *task, enum pid_type type, |
| 380 | struct pid *pid) |
| 381 | { |
| 382 | struct pid_link *link; |
| 383 | |
| 384 | link = &task->pids[type]; |
| 385 | link->pid = pid; |
| 386 | hlist_add_head_rcu(&link->node, &pid->tasks[type]); |
| 387 | } |
| 388 | |
| 389 | static void __change_pid(struct task_struct *task, enum pid_type type, |
| 390 | struct pid *new) |
| 391 | { |
| 392 | struct pid_link *link; |
| 393 | struct pid *pid; |
| 394 | int tmp; |
| 395 | |
| 396 | link = &task->pids[type]; |
| 397 | pid = link->pid; |
| 398 | |
| 399 | hlist_del_rcu(&link->node); |
| 400 | link->pid = new; |
| 401 | |
| 402 | for (tmp = PIDTYPE_MAX; --tmp >= 0; ) |
| 403 | if (!hlist_empty(&pid->tasks[tmp])) |
| 404 | return; |
| 405 | |
| 406 | free_pid(pid); |
| 407 | } |
| 408 | |
| 409 | void detach_pid(struct task_struct *task, enum pid_type type) |
| 410 | { |
| 411 | __change_pid(task, type, NULL); |
| 412 | } |
| 413 | |
| 414 | void change_pid(struct task_struct *task, enum pid_type type, |
| 415 | struct pid *pid) |
| 416 | { |
| 417 | __change_pid(task, type, pid); |
| 418 | attach_pid(task, type, pid); |
| 419 | } |
| 420 | |
| 421 | /* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */ |
| 422 | void transfer_pid(struct task_struct *old, struct task_struct *new, |
| 423 | enum pid_type type) |
| 424 | { |
| 425 | new->pids[type].pid = old->pids[type].pid; |
| 426 | hlist_replace_rcu(&old->pids[type].node, &new->pids[type].node); |
| 427 | } |
| 428 | |
| 429 | struct task_struct *pid_task(struct pid *pid, enum pid_type type) |
| 430 | { |
| 431 | struct task_struct *result = NULL; |
| 432 | if (pid) { |
| 433 | struct hlist_node *first; |
| 434 | first = rcu_dereference_check(hlist_first_rcu(&pid->tasks[type]), |
| 435 | lockdep_tasklist_lock_is_held()); |
| 436 | if (first) |
| 437 | result = hlist_entry(first, struct task_struct, pids[(type)].node); |
| 438 | } |
| 439 | return result; |
| 440 | } |
| 441 | EXPORT_SYMBOL(pid_task); |
| 442 | |
| 443 | /* |
| 444 | * Must be called under rcu_read_lock(). |
| 445 | */ |
| 446 | struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns) |
| 447 | { |
| 448 | rcu_lockdep_assert(rcu_read_lock_held(), |
| 449 | "find_task_by_pid_ns() needs rcu_read_lock()" |
| 450 | " protection"); |
| 451 | return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID); |
| 452 | } |
| 453 | EXPORT_SYMBOL_GPL(find_task_by_pid_ns); |
| 454 | |
| 455 | struct task_struct *find_task_by_vpid(pid_t vnr) |
| 456 | { |
| 457 | return find_task_by_pid_ns(vnr, task_active_pid_ns(current)); |
| 458 | } |
| 459 | |
| 460 | struct pid *get_task_pid(struct task_struct *task, enum pid_type type) |
| 461 | { |
| 462 | struct pid *pid; |
| 463 | rcu_read_lock(); |
| 464 | if (type != PIDTYPE_PID) |
| 465 | task = task->group_leader; |
| 466 | pid = get_pid(task->pids[type].pid); |
| 467 | rcu_read_unlock(); |
| 468 | return pid; |
| 469 | } |
| 470 | EXPORT_SYMBOL_GPL(get_task_pid); |
| 471 | |
| 472 | struct task_struct *get_pid_task(struct pid *pid, enum pid_type type) |
| 473 | { |
| 474 | struct task_struct *result; |
| 475 | rcu_read_lock(); |
| 476 | result = pid_task(pid, type); |
| 477 | if (result) |
| 478 | get_task_struct(result); |
| 479 | rcu_read_unlock(); |
| 480 | return result; |
| 481 | } |
| 482 | EXPORT_SYMBOL_GPL(get_pid_task); |
| 483 | |
| 484 | struct pid *find_get_pid(pid_t nr) |
| 485 | { |
| 486 | struct pid *pid; |
| 487 | |
| 488 | rcu_read_lock(); |
| 489 | pid = get_pid(find_vpid(nr)); |
| 490 | rcu_read_unlock(); |
| 491 | |
| 492 | return pid; |
| 493 | } |
| 494 | EXPORT_SYMBOL_GPL(find_get_pid); |
| 495 | |
| 496 | pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns) |
| 497 | { |
| 498 | struct upid *upid; |
| 499 | pid_t nr = 0; |
| 500 | |
| 501 | if (pid && ns->level <= pid->level) { |
| 502 | upid = &pid->numbers[ns->level]; |
| 503 | if (upid->ns == ns) |
| 504 | nr = upid->nr; |
| 505 | } |
| 506 | return nr; |
| 507 | } |
| 508 | EXPORT_SYMBOL_GPL(pid_nr_ns); |
| 509 | |
| 510 | pid_t pid_vnr(struct pid *pid) |
| 511 | { |
| 512 | return pid_nr_ns(pid, task_active_pid_ns(current)); |
| 513 | } |
| 514 | EXPORT_SYMBOL_GPL(pid_vnr); |
| 515 | |
| 516 | pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type, |
| 517 | struct pid_namespace *ns) |
| 518 | { |
| 519 | pid_t nr = 0; |
| 520 | |
| 521 | rcu_read_lock(); |
| 522 | if (!ns) |
| 523 | ns = task_active_pid_ns(current); |
| 524 | if (likely(pid_alive(task))) { |
| 525 | if (type != PIDTYPE_PID) |
| 526 | task = task->group_leader; |
| 527 | nr = pid_nr_ns(task->pids[type].pid, ns); |
| 528 | } |
| 529 | rcu_read_unlock(); |
| 530 | |
| 531 | return nr; |
| 532 | } |
| 533 | EXPORT_SYMBOL(__task_pid_nr_ns); |
| 534 | |
| 535 | pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns) |
| 536 | { |
| 537 | return pid_nr_ns(task_tgid(tsk), ns); |
| 538 | } |
| 539 | EXPORT_SYMBOL(task_tgid_nr_ns); |
| 540 | |
| 541 | struct pid_namespace *task_active_pid_ns(struct task_struct *tsk) |
| 542 | { |
| 543 | return ns_of_pid(task_pid(tsk)); |
| 544 | } |
| 545 | EXPORT_SYMBOL_GPL(task_active_pid_ns); |
| 546 | |
| 547 | /* |
| 548 | * Used by proc to find the first pid that is greater than or equal to nr. |
| 549 | * |
| 550 | * If there is a pid at nr this function is exactly the same as find_pid_ns. |
| 551 | */ |
| 552 | struct pid *find_ge_pid(int nr, struct pid_namespace *ns) |
| 553 | { |
| 554 | struct pid *pid; |
| 555 | |
| 556 | do { |
| 557 | pid = find_pid_ns(nr, ns); |
| 558 | if (pid) |
| 559 | break; |
| 560 | nr = next_pidmap(ns, nr); |
| 561 | } while (nr > 0); |
| 562 | |
| 563 | return pid; |
| 564 | } |
| 565 | |
| 566 | /* |
| 567 | * The pid hash table is scaled according to the amount of memory in the |
| 568 | * machine. From a minimum of 16 slots up to 4096 slots at one gigabyte or |
| 569 | * more. |
| 570 | */ |
| 571 | void __init pidhash_init(void) |
| 572 | { |
| 573 | unsigned int i, pidhash_size; |
| 574 | |
| 575 | pid_hash = alloc_large_system_hash("PID", sizeof(*pid_hash), 0, 18, |
| 576 | HASH_EARLY | HASH_SMALL, |
| 577 | &pidhash_shift, NULL, |
| 578 | 0, 4096); |
| 579 | pidhash_size = 1U << pidhash_shift; |
| 580 | |
| 581 | for (i = 0; i < pidhash_size; i++) |
| 582 | INIT_HLIST_HEAD(&pid_hash[i]); |
| 583 | } |
| 584 | |
| 585 | void __init pidmap_init(void) |
| 586 | { |
| 587 | /* Veryify no one has done anything silly */ |
| 588 | BUILD_BUG_ON(PID_MAX_LIMIT >= PIDNS_HASH_ADDING); |
| 589 | |
| 590 | /* bump default and minimum pid_max based on number of cpus */ |
| 591 | pid_max = min(pid_max_max, max_t(int, pid_max, |
| 592 | PIDS_PER_CPU_DEFAULT * num_possible_cpus())); |
| 593 | pid_max_min = max_t(int, pid_max_min, |
| 594 | PIDS_PER_CPU_MIN * num_possible_cpus()); |
| 595 | pr_info("pid_max: default: %u minimum: %u\n", pid_max, pid_max_min); |
| 596 | |
| 597 | init_pid_ns.pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL); |
| 598 | /* Reserve PID 0. We never call free_pidmap(0) */ |
| 599 | set_bit(0, init_pid_ns.pidmap[0].page); |
| 600 | atomic_dec(&init_pid_ns.pidmap[0].nr_free); |
| 601 | init_pid_ns.nr_hashed = PIDNS_HASH_ADDING; |
| 602 | |
| 603 | init_pid_ns.pid_cachep = KMEM_CACHE(pid, |
| 604 | SLAB_HWCACHE_ALIGN | SLAB_PANIC); |
| 605 | } |