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![Pavel Emelyanov](/assets/img/avatar_default.png)
Since these are expanded into call to pid_nr_ns() anyway, it's OK to move the whole routine out-of-line. This is a cheap way to save ~100 bytes from vmlinux. Together with the previous two patches, it saves half-a-kilo from the vmlinux. Un-inline other (currently inlined) functions must be done with additional performance testing. Signed-off-by: Pavel Emelyanov <xemul@openvz.org> Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: Paul Menage <menage@google.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
699 lines
17 KiB
C
699 lines
17 KiB
C
/*
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* Generic pidhash and scalable, time-bounded PID allocator
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*
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* (C) 2002-2003 William Irwin, IBM
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* (C) 2004 William Irwin, Oracle
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* (C) 2002-2004 Ingo Molnar, Red Hat
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*
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* pid-structures are backing objects for tasks sharing a given ID to chain
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* against. There is very little to them aside from hashing them and
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* parking tasks using given ID's on a list.
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*
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* The hash is always changed with the tasklist_lock write-acquired,
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* and the hash is only accessed with the tasklist_lock at least
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* read-acquired, so there's no additional SMP locking needed here.
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*
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* We have a list of bitmap pages, which bitmaps represent the PID space.
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* Allocating and freeing PIDs is completely lockless. The worst-case
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* allocation scenario when all but one out of 1 million PIDs possible are
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* allocated already: the scanning of 32 list entries and at most PAGE_SIZE
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* bytes. The typical fastpath is a single successful setbit. Freeing is O(1).
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*
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* Pid namespaces:
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* (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
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* (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
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* Many thanks to Oleg Nesterov for comments and help
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*
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*/
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/bootmem.h>
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#include <linux/hash.h>
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#include <linux/pid_namespace.h>
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#include <linux/init_task.h>
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#include <linux/syscalls.h>
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#define pid_hashfn(nr, ns) \
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hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift)
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static struct hlist_head *pid_hash;
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static int pidhash_shift;
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struct pid init_struct_pid = INIT_STRUCT_PID;
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static struct kmem_cache *pid_ns_cachep;
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int pid_max = PID_MAX_DEFAULT;
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#define RESERVED_PIDS 300
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int pid_max_min = RESERVED_PIDS + 1;
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int pid_max_max = PID_MAX_LIMIT;
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#define BITS_PER_PAGE (PAGE_SIZE*8)
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#define BITS_PER_PAGE_MASK (BITS_PER_PAGE-1)
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static inline int mk_pid(struct pid_namespace *pid_ns,
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struct pidmap *map, int off)
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{
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return (map - pid_ns->pidmap)*BITS_PER_PAGE + off;
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}
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#define find_next_offset(map, off) \
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find_next_zero_bit((map)->page, BITS_PER_PAGE, off)
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/*
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* PID-map pages start out as NULL, they get allocated upon
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* first use and are never deallocated. This way a low pid_max
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* value does not cause lots of bitmaps to be allocated, but
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* the scheme scales to up to 4 million PIDs, runtime.
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*/
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struct pid_namespace init_pid_ns = {
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.kref = {
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.refcount = ATOMIC_INIT(2),
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},
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.pidmap = {
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[ 0 ... PIDMAP_ENTRIES-1] = { ATOMIC_INIT(BITS_PER_PAGE), NULL }
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},
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.last_pid = 0,
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.level = 0,
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.child_reaper = &init_task,
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};
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EXPORT_SYMBOL_GPL(init_pid_ns);
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int is_container_init(struct task_struct *tsk)
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{
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int ret = 0;
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struct pid *pid;
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rcu_read_lock();
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pid = task_pid(tsk);
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if (pid != NULL && pid->numbers[pid->level].nr == 1)
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ret = 1;
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rcu_read_unlock();
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return ret;
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}
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EXPORT_SYMBOL(is_container_init);
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/*
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* Note: disable interrupts while the pidmap_lock is held as an
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* interrupt might come in and do read_lock(&tasklist_lock).
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*
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* If we don't disable interrupts there is a nasty deadlock between
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* detach_pid()->free_pid() and another cpu that does
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* spin_lock(&pidmap_lock) followed by an interrupt routine that does
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* read_lock(&tasklist_lock);
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*
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* After we clean up the tasklist_lock and know there are no
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* irq handlers that take it we can leave the interrupts enabled.
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* For now it is easier to be safe than to prove it can't happen.
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*/
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static __cacheline_aligned_in_smp DEFINE_SPINLOCK(pidmap_lock);
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static fastcall void free_pidmap(struct pid_namespace *pid_ns, int pid)
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{
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struct pidmap *map = pid_ns->pidmap + pid / BITS_PER_PAGE;
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int offset = pid & BITS_PER_PAGE_MASK;
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clear_bit(offset, map->page);
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atomic_inc(&map->nr_free);
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}
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static int alloc_pidmap(struct pid_namespace *pid_ns)
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{
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int i, offset, max_scan, pid, last = pid_ns->last_pid;
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struct pidmap *map;
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pid = last + 1;
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if (pid >= pid_max)
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pid = RESERVED_PIDS;
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offset = pid & BITS_PER_PAGE_MASK;
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map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
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max_scan = (pid_max + BITS_PER_PAGE - 1)/BITS_PER_PAGE - !offset;
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for (i = 0; i <= max_scan; ++i) {
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if (unlikely(!map->page)) {
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void *page = kzalloc(PAGE_SIZE, GFP_KERNEL);
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/*
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* Free the page if someone raced with us
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* installing it:
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*/
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spin_lock_irq(&pidmap_lock);
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if (map->page)
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kfree(page);
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else
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map->page = page;
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spin_unlock_irq(&pidmap_lock);
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if (unlikely(!map->page))
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break;
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}
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if (likely(atomic_read(&map->nr_free))) {
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do {
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if (!test_and_set_bit(offset, map->page)) {
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atomic_dec(&map->nr_free);
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pid_ns->last_pid = pid;
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return pid;
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}
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offset = find_next_offset(map, offset);
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pid = mk_pid(pid_ns, map, offset);
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/*
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* find_next_offset() found a bit, the pid from it
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* is in-bounds, and if we fell back to the last
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* bitmap block and the final block was the same
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* as the starting point, pid is before last_pid.
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*/
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} while (offset < BITS_PER_PAGE && pid < pid_max &&
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(i != max_scan || pid < last ||
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!((last+1) & BITS_PER_PAGE_MASK)));
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}
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if (map < &pid_ns->pidmap[(pid_max-1)/BITS_PER_PAGE]) {
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++map;
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offset = 0;
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} else {
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map = &pid_ns->pidmap[0];
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offset = RESERVED_PIDS;
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if (unlikely(last == offset))
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break;
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}
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pid = mk_pid(pid_ns, map, offset);
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}
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return -1;
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}
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static int next_pidmap(struct pid_namespace *pid_ns, int last)
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{
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int offset;
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struct pidmap *map, *end;
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offset = (last + 1) & BITS_PER_PAGE_MASK;
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map = &pid_ns->pidmap[(last + 1)/BITS_PER_PAGE];
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end = &pid_ns->pidmap[PIDMAP_ENTRIES];
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for (; map < end; map++, offset = 0) {
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if (unlikely(!map->page))
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continue;
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offset = find_next_bit((map)->page, BITS_PER_PAGE, offset);
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if (offset < BITS_PER_PAGE)
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return mk_pid(pid_ns, map, offset);
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}
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return -1;
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}
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fastcall void put_pid(struct pid *pid)
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{
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struct pid_namespace *ns;
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if (!pid)
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return;
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ns = pid->numbers[pid->level].ns;
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if ((atomic_read(&pid->count) == 1) ||
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atomic_dec_and_test(&pid->count)) {
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kmem_cache_free(ns->pid_cachep, pid);
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put_pid_ns(ns);
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}
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}
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EXPORT_SYMBOL_GPL(put_pid);
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static void delayed_put_pid(struct rcu_head *rhp)
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{
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struct pid *pid = container_of(rhp, struct pid, rcu);
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put_pid(pid);
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}
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fastcall void free_pid(struct pid *pid)
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{
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/* We can be called with write_lock_irq(&tasklist_lock) held */
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int i;
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unsigned long flags;
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spin_lock_irqsave(&pidmap_lock, flags);
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for (i = 0; i <= pid->level; i++)
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hlist_del_rcu(&pid->numbers[i].pid_chain);
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spin_unlock_irqrestore(&pidmap_lock, flags);
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for (i = 0; i <= pid->level; i++)
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free_pidmap(pid->numbers[i].ns, pid->numbers[i].nr);
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call_rcu(&pid->rcu, delayed_put_pid);
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}
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struct pid *alloc_pid(struct pid_namespace *ns)
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{
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struct pid *pid;
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enum pid_type type;
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int i, nr;
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struct pid_namespace *tmp;
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struct upid *upid;
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pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
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if (!pid)
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goto out;
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tmp = ns;
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for (i = ns->level; i >= 0; i--) {
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nr = alloc_pidmap(tmp);
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if (nr < 0)
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goto out_free;
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pid->numbers[i].nr = nr;
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pid->numbers[i].ns = tmp;
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tmp = tmp->parent;
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}
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get_pid_ns(ns);
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pid->level = ns->level;
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atomic_set(&pid->count, 1);
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for (type = 0; type < PIDTYPE_MAX; ++type)
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INIT_HLIST_HEAD(&pid->tasks[type]);
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spin_lock_irq(&pidmap_lock);
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for (i = ns->level; i >= 0; i--) {
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upid = &pid->numbers[i];
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hlist_add_head_rcu(&upid->pid_chain,
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&pid_hash[pid_hashfn(upid->nr, upid->ns)]);
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}
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spin_unlock_irq(&pidmap_lock);
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out:
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return pid;
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out_free:
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for (i++; i <= ns->level; i++)
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free_pidmap(pid->numbers[i].ns, pid->numbers[i].nr);
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kmem_cache_free(ns->pid_cachep, pid);
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pid = NULL;
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goto out;
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}
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struct pid * fastcall find_pid_ns(int nr, struct pid_namespace *ns)
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{
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struct hlist_node *elem;
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struct upid *pnr;
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hlist_for_each_entry_rcu(pnr, elem,
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&pid_hash[pid_hashfn(nr, ns)], pid_chain)
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if (pnr->nr == nr && pnr->ns == ns)
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return container_of(pnr, struct pid,
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numbers[ns->level]);
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return NULL;
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}
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EXPORT_SYMBOL_GPL(find_pid_ns);
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struct pid *find_vpid(int nr)
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{
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return find_pid_ns(nr, current->nsproxy->pid_ns);
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}
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EXPORT_SYMBOL_GPL(find_vpid);
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struct pid *find_pid(int nr)
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{
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return find_pid_ns(nr, &init_pid_ns);
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}
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EXPORT_SYMBOL_GPL(find_pid);
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/*
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* attach_pid() must be called with the tasklist_lock write-held.
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*/
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int fastcall attach_pid(struct task_struct *task, enum pid_type type,
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struct pid *pid)
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{
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struct pid_link *link;
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link = &task->pids[type];
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link->pid = pid;
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hlist_add_head_rcu(&link->node, &pid->tasks[type]);
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return 0;
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}
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void fastcall detach_pid(struct task_struct *task, enum pid_type type)
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{
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struct pid_link *link;
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struct pid *pid;
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int tmp;
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link = &task->pids[type];
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pid = link->pid;
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hlist_del_rcu(&link->node);
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link->pid = NULL;
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for (tmp = PIDTYPE_MAX; --tmp >= 0; )
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if (!hlist_empty(&pid->tasks[tmp]))
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return;
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free_pid(pid);
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}
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/* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */
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void fastcall transfer_pid(struct task_struct *old, struct task_struct *new,
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enum pid_type type)
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{
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new->pids[type].pid = old->pids[type].pid;
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hlist_replace_rcu(&old->pids[type].node, &new->pids[type].node);
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old->pids[type].pid = NULL;
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}
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struct task_struct * fastcall pid_task(struct pid *pid, enum pid_type type)
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{
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struct task_struct *result = NULL;
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if (pid) {
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struct hlist_node *first;
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first = rcu_dereference(pid->tasks[type].first);
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if (first)
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result = hlist_entry(first, struct task_struct, pids[(type)].node);
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}
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return result;
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}
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/*
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* Must be called under rcu_read_lock() or with tasklist_lock read-held.
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*/
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struct task_struct *find_task_by_pid_type_ns(int type, int nr,
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struct pid_namespace *ns)
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{
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return pid_task(find_pid_ns(nr, ns), type);
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}
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EXPORT_SYMBOL(find_task_by_pid_type_ns);
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struct task_struct *find_task_by_pid(pid_t nr)
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{
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return find_task_by_pid_type_ns(PIDTYPE_PID, nr, &init_pid_ns);
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}
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EXPORT_SYMBOL(find_task_by_pid);
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struct task_struct *find_task_by_vpid(pid_t vnr)
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{
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return find_task_by_pid_type_ns(PIDTYPE_PID, vnr,
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current->nsproxy->pid_ns);
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}
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EXPORT_SYMBOL(find_task_by_vpid);
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struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
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{
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return find_task_by_pid_type_ns(PIDTYPE_PID, nr, ns);
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}
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EXPORT_SYMBOL(find_task_by_pid_ns);
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struct pid *get_task_pid(struct task_struct *task, enum pid_type type)
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{
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struct pid *pid;
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rcu_read_lock();
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pid = get_pid(task->pids[type].pid);
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rcu_read_unlock();
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return pid;
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}
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struct task_struct *fastcall get_pid_task(struct pid *pid, enum pid_type type)
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{
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struct task_struct *result;
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rcu_read_lock();
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result = pid_task(pid, type);
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if (result)
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get_task_struct(result);
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rcu_read_unlock();
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return result;
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}
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struct pid *find_get_pid(pid_t nr)
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{
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struct pid *pid;
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rcu_read_lock();
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pid = get_pid(find_vpid(nr));
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rcu_read_unlock();
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return pid;
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}
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pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns)
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{
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struct upid *upid;
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pid_t nr = 0;
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if (pid && ns->level <= pid->level) {
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upid = &pid->numbers[ns->level];
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if (upid->ns == ns)
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nr = upid->nr;
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}
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return nr;
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}
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pid_t task_pid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
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{
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return pid_nr_ns(task_pid(tsk), ns);
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}
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EXPORT_SYMBOL(task_pid_nr_ns);
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pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
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{
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return pid_nr_ns(task_tgid(tsk), ns);
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}
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EXPORT_SYMBOL(task_tgid_nr_ns);
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pid_t task_pgrp_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
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{
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return pid_nr_ns(task_pgrp(tsk), ns);
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}
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EXPORT_SYMBOL(task_pgrp_nr_ns);
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pid_t task_session_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
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{
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return pid_nr_ns(task_session(tsk), ns);
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}
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EXPORT_SYMBOL(task_session_nr_ns);
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/*
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* Used by proc to find the first pid that is greater then or equal to nr.
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*
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* If there is a pid at nr this function is exactly the same as find_pid.
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*/
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struct pid *find_ge_pid(int nr, struct pid_namespace *ns)
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{
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struct pid *pid;
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do {
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pid = find_pid_ns(nr, ns);
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if (pid)
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break;
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nr = next_pidmap(ns, nr);
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} while (nr > 0);
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return pid;
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}
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EXPORT_SYMBOL_GPL(find_get_pid);
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struct pid_cache {
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int nr_ids;
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char name[16];
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struct kmem_cache *cachep;
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struct list_head list;
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};
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static LIST_HEAD(pid_caches_lh);
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static DEFINE_MUTEX(pid_caches_mutex);
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/*
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* creates the kmem cache to allocate pids from.
|
|
* @nr_ids: the number of numerical ids this pid will have to carry
|
|
*/
|
|
|
|
static struct kmem_cache *create_pid_cachep(int nr_ids)
|
|
{
|
|
struct pid_cache *pcache;
|
|
struct kmem_cache *cachep;
|
|
|
|
mutex_lock(&pid_caches_mutex);
|
|
list_for_each_entry (pcache, &pid_caches_lh, list)
|
|
if (pcache->nr_ids == nr_ids)
|
|
goto out;
|
|
|
|
pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
|
|
if (pcache == NULL)
|
|
goto err_alloc;
|
|
|
|
snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
|
|
cachep = kmem_cache_create(pcache->name,
|
|
sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
|
|
0, SLAB_HWCACHE_ALIGN, NULL);
|
|
if (cachep == NULL)
|
|
goto err_cachep;
|
|
|
|
pcache->nr_ids = nr_ids;
|
|
pcache->cachep = cachep;
|
|
list_add(&pcache->list, &pid_caches_lh);
|
|
out:
|
|
mutex_unlock(&pid_caches_mutex);
|
|
return pcache->cachep;
|
|
|
|
err_cachep:
|
|
kfree(pcache);
|
|
err_alloc:
|
|
mutex_unlock(&pid_caches_mutex);
|
|
return NULL;
|
|
}
|
|
|
|
static struct pid_namespace *create_pid_namespace(int level)
|
|
{
|
|
struct pid_namespace *ns;
|
|
int i;
|
|
|
|
ns = kmem_cache_alloc(pid_ns_cachep, GFP_KERNEL);
|
|
if (ns == NULL)
|
|
goto out;
|
|
|
|
ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
|
|
if (!ns->pidmap[0].page)
|
|
goto out_free;
|
|
|
|
ns->pid_cachep = create_pid_cachep(level + 1);
|
|
if (ns->pid_cachep == NULL)
|
|
goto out_free_map;
|
|
|
|
kref_init(&ns->kref);
|
|
ns->last_pid = 0;
|
|
ns->child_reaper = NULL;
|
|
ns->level = level;
|
|
|
|
set_bit(0, ns->pidmap[0].page);
|
|
atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
|
|
|
|
for (i = 1; i < PIDMAP_ENTRIES; i++) {
|
|
ns->pidmap[i].page = 0;
|
|
atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
|
|
}
|
|
|
|
return ns;
|
|
|
|
out_free_map:
|
|
kfree(ns->pidmap[0].page);
|
|
out_free:
|
|
kmem_cache_free(pid_ns_cachep, ns);
|
|
out:
|
|
return ERR_PTR(-ENOMEM);
|
|
}
|
|
|
|
static void destroy_pid_namespace(struct pid_namespace *ns)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < PIDMAP_ENTRIES; i++)
|
|
kfree(ns->pidmap[i].page);
|
|
kmem_cache_free(pid_ns_cachep, ns);
|
|
}
|
|
|
|
struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
|
|
{
|
|
struct pid_namespace *new_ns;
|
|
|
|
BUG_ON(!old_ns);
|
|
new_ns = get_pid_ns(old_ns);
|
|
if (!(flags & CLONE_NEWPID))
|
|
goto out;
|
|
|
|
new_ns = ERR_PTR(-EINVAL);
|
|
if (flags & CLONE_THREAD)
|
|
goto out_put;
|
|
|
|
new_ns = create_pid_namespace(old_ns->level + 1);
|
|
if (!IS_ERR(new_ns))
|
|
new_ns->parent = get_pid_ns(old_ns);
|
|
|
|
out_put:
|
|
put_pid_ns(old_ns);
|
|
out:
|
|
return new_ns;
|
|
}
|
|
|
|
void free_pid_ns(struct kref *kref)
|
|
{
|
|
struct pid_namespace *ns, *parent;
|
|
|
|
ns = container_of(kref, struct pid_namespace, kref);
|
|
|
|
parent = ns->parent;
|
|
destroy_pid_namespace(ns);
|
|
|
|
if (parent != NULL)
|
|
put_pid_ns(parent);
|
|
}
|
|
|
|
void zap_pid_ns_processes(struct pid_namespace *pid_ns)
|
|
{
|
|
int nr;
|
|
int rc;
|
|
|
|
/*
|
|
* The last thread in the cgroup-init thread group is terminating.
|
|
* Find remaining pid_ts in the namespace, signal and wait for them
|
|
* to exit.
|
|
*
|
|
* Note: This signals each threads in the namespace - even those that
|
|
* belong to the same thread group, To avoid this, we would have
|
|
* to walk the entire tasklist looking a processes in this
|
|
* namespace, but that could be unnecessarily expensive if the
|
|
* pid namespace has just a few processes. Or we need to
|
|
* maintain a tasklist for each pid namespace.
|
|
*
|
|
*/
|
|
read_lock(&tasklist_lock);
|
|
nr = next_pidmap(pid_ns, 1);
|
|
while (nr > 0) {
|
|
kill_proc_info(SIGKILL, SEND_SIG_PRIV, nr);
|
|
nr = next_pidmap(pid_ns, nr);
|
|
}
|
|
read_unlock(&tasklist_lock);
|
|
|
|
do {
|
|
clear_thread_flag(TIF_SIGPENDING);
|
|
rc = sys_wait4(-1, NULL, __WALL, NULL);
|
|
} while (rc != -ECHILD);
|
|
|
|
|
|
/* Child reaper for the pid namespace is going away */
|
|
pid_ns->child_reaper = NULL;
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* The pid hash table is scaled according to the amount of memory in the
|
|
* machine. From a minimum of 16 slots up to 4096 slots at one gigabyte or
|
|
* more.
|
|
*/
|
|
void __init pidhash_init(void)
|
|
{
|
|
int i, pidhash_size;
|
|
unsigned long megabytes = nr_kernel_pages >> (20 - PAGE_SHIFT);
|
|
|
|
pidhash_shift = max(4, fls(megabytes * 4));
|
|
pidhash_shift = min(12, pidhash_shift);
|
|
pidhash_size = 1 << pidhash_shift;
|
|
|
|
printk("PID hash table entries: %d (order: %d, %Zd bytes)\n",
|
|
pidhash_size, pidhash_shift,
|
|
pidhash_size * sizeof(struct hlist_head));
|
|
|
|
pid_hash = alloc_bootmem(pidhash_size * sizeof(*(pid_hash)));
|
|
if (!pid_hash)
|
|
panic("Could not alloc pidhash!\n");
|
|
for (i = 0; i < pidhash_size; i++)
|
|
INIT_HLIST_HEAD(&pid_hash[i]);
|
|
}
|
|
|
|
void __init pidmap_init(void)
|
|
{
|
|
init_pid_ns.pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
|
|
/* Reserve PID 0. We never call free_pidmap(0) */
|
|
set_bit(0, init_pid_ns.pidmap[0].page);
|
|
atomic_dec(&init_pid_ns.pidmap[0].nr_free);
|
|
|
|
init_pid_ns.pid_cachep = create_pid_cachep(1);
|
|
if (init_pid_ns.pid_cachep == NULL)
|
|
panic("Can't create pid_1 cachep\n");
|
|
|
|
pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
|
|
}
|