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![Arnd Bergmann](/assets/img/avatar_default.png)
Most users of IS_ERR_VALUE() in the kernel are wrong, as they pass an 'int' into a function that takes an 'unsigned long' argument. This happens to work because the type is sign-extended on 64-bit architectures before it gets converted into an unsigned type. However, anything that passes an 'unsigned short' or 'unsigned int' argument into IS_ERR_VALUE() is guaranteed to be broken, as are 8-bit integers and types that are wider than 'unsigned long'. Andrzej Hajda has already fixed a lot of the worst abusers that were causing actual bugs, but it would be nice to prevent any users that are not passing 'unsigned long' arguments. This patch changes all users of IS_ERR_VALUE() that I could find on 32-bit ARM randconfig builds and x86 allmodconfig. For the moment, this doesn't change the definition of IS_ERR_VALUE() because there are probably still architecture specific users elsewhere. Almost all the warnings I got are for files that are better off using 'if (err)' or 'if (err < 0)'. The only legitimate user I could find that we get a warning for is the (32-bit only) freescale fman driver, so I did not remove the IS_ERR_VALUE() there but changed the type to 'unsigned long'. For 9pfs, I just worked around one user whose calling conventions are so obscure that I did not dare change the behavior. I was using this definition for testing: #define IS_ERR_VALUE(x) ((unsigned long*)NULL == (typeof (x)*)NULL && \ unlikely((unsigned long long)(x) >= (unsigned long long)(typeof(x))-MAX_ERRNO)) which ends up making all 16-bit or wider types work correctly with the most plausible interpretation of what IS_ERR_VALUE() was supposed to return according to its users, but also causes a compile-time warning for any users that do not pass an 'unsigned long' argument. I suggested this approach earlier this year, but back then we ended up deciding to just fix the users that are obviously broken. After the initial warning that caused me to get involved in the discussion (fs/gfs2/dir.c) showed up again in the mainline kernel, Linus asked me to send the whole thing again. [ Updated the 9p parts as per Al Viro - Linus ] Signed-off-by: Arnd Bergmann <arnd@arndb.de> Cc: Andrzej Hajda <a.hajda@samsung.com> Cc: Andrew Morton <akpm@linux-foundation.org> Link: https://lkml.org/lkml/2016/1/7/363 Link: https://lkml.org/lkml/2016/5/27/486 Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> # For nvmem part Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
608 lines
15 KiB
C
608 lines
15 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 Nadia Yvette Chambers, IBM
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* (C) 2004 Nadia Yvette Chambers, 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/export.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/rculist.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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#include <linux/proc_ns.h>
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#include <linux/proc_fs.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 unsigned int pidhash_shift = 4;
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struct pid init_struct_pid = INIT_STRUCT_PID;
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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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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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.nr_hashed = PIDNS_HASH_ADDING,
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.level = 0,
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.child_reaper = &init_task,
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.user_ns = &init_user_ns,
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.ns.inum = PROC_PID_INIT_INO,
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#ifdef CONFIG_PID_NS
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.ns.ops = &pidns_operations,
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#endif
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};
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EXPORT_SYMBOL_GPL(init_pid_ns);
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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 void free_pidmap(struct upid *upid)
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{
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int nr = upid->nr;
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struct pidmap *map = upid->ns->pidmap + nr / BITS_PER_PAGE;
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int offset = nr & 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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/*
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* If we started walking pids at 'base', is 'a' seen before 'b'?
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*/
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static int pid_before(int base, int a, int b)
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{
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/*
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* This is the same as saying
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*
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* (a - base + MAXUINT) % MAXUINT < (b - base + MAXUINT) % MAXUINT
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* and that mapping orders 'a' and 'b' with respect to 'base'.
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*/
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return (unsigned)(a - base) < (unsigned)(b - base);
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}
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/*
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* We might be racing with someone else trying to set pid_ns->last_pid
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* at the pid allocation time (there's also a sysctl for this, but racing
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* with this one is OK, see comment in kernel/pid_namespace.c about it).
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* We want the winner to have the "later" value, because if the
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* "earlier" value prevails, then a pid may get reused immediately.
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*
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* Since pids rollover, it is not sufficient to just pick the bigger
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* value. We have to consider where we started counting from.
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*
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* 'base' is the value of pid_ns->last_pid that we observed when
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* we started looking for a pid.
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*
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* 'pid' is the pid that we eventually found.
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*/
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static void set_last_pid(struct pid_namespace *pid_ns, int base, int pid)
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{
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int prev;
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int last_write = base;
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do {
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prev = last_write;
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last_write = cmpxchg(&pid_ns->last_pid, prev, pid);
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} while ((prev != last_write) && (pid_before(base, last_write, pid)));
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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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/*
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* If last_pid points into the middle of the map->page we
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* want to scan this bitmap block twice, the second time
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* we start with offset == 0 (or RESERVED_PIDS).
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*/
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max_scan = DIV_ROUND_UP(pid_max, 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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map->page = page;
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page = NULL;
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}
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spin_unlock_irq(&pidmap_lock);
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kfree(page);
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if (unlikely(!map->page))
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return -ENOMEM;
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}
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if (likely(atomic_read(&map->nr_free))) {
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for ( ; ; ) {
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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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set_last_pid(pid_ns, last, 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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if (offset >= BITS_PER_PAGE)
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break;
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pid = mk_pid(pid_ns, map, offset);
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if (pid >= pid_max)
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break;
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}
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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 -EAGAIN;
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}
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int next_pidmap(struct pid_namespace *pid_ns, unsigned int last)
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{
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int offset;
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struct pidmap *map, *end;
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if (last >= PID_MAX_LIMIT)
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return -1;
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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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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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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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struct upid *upid = pid->numbers + i;
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struct pid_namespace *ns = upid->ns;
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hlist_del_rcu(&upid->pid_chain);
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switch(--ns->nr_hashed) {
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case 2:
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case 1:
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/* When all that is left in the pid namespace
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* is the reaper wake up the reaper. The reaper
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* may be sleeping in zap_pid_ns_processes().
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*/
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wake_up_process(ns->child_reaper);
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break;
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case PIDNS_HASH_ADDING:
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/* Handle a fork failure of the first process */
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WARN_ON(ns->child_reaper);
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ns->nr_hashed = 0;
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/* fall through */
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case 0:
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schedule_work(&ns->proc_work);
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break;
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}
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}
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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);
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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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int retval = -ENOMEM;
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pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
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if (!pid)
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return ERR_PTR(retval);
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tmp = ns;
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pid->level = ns->level;
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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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retval = nr;
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goto out_free;
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}
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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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if (unlikely(is_child_reaper(pid))) {
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if (pid_ns_prepare_proc(ns))
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goto out_free;
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}
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get_pid_ns(ns);
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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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upid = pid->numbers + ns->level;
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spin_lock_irq(&pidmap_lock);
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if (!(ns->nr_hashed & PIDNS_HASH_ADDING))
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goto out_unlock;
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for ( ; upid >= pid->numbers; --upid) {
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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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upid->ns->nr_hashed++;
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}
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spin_unlock_irq(&pidmap_lock);
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return pid;
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out_unlock:
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spin_unlock_irq(&pidmap_lock);
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put_pid_ns(ns);
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out_free:
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while (++i <= ns->level)
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free_pidmap(pid->numbers + i);
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kmem_cache_free(ns->pid_cachep, pid);
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return ERR_PTR(retval);
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}
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void disable_pid_allocation(struct pid_namespace *ns)
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{
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spin_lock_irq(&pidmap_lock);
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ns->nr_hashed &= ~PIDNS_HASH_ADDING;
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spin_unlock_irq(&pidmap_lock);
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}
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struct pid *find_pid_ns(int nr, struct pid_namespace *ns)
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{
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struct upid *pnr;
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hlist_for_each_entry_rcu(pnr,
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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, task_active_pid_ns(current));
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}
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EXPORT_SYMBOL_GPL(find_vpid);
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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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void attach_pid(struct task_struct *task, enum pid_type type)
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{
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struct pid_link *link = &task->pids[type];
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hlist_add_head_rcu(&link->node, &link->pid->tasks[type]);
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}
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static void __change_pid(struct task_struct *task, enum pid_type type,
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struct pid *new)
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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 = new;
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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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void detach_pid(struct task_struct *task, enum pid_type type)
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{
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__change_pid(task, type, NULL);
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}
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void change_pid(struct task_struct *task, enum pid_type type,
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struct pid *pid)
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{
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__change_pid(task, type, pid);
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attach_pid(task, type);
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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 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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}
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struct task_struct *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_check(hlist_first_rcu(&pid->tasks[type]),
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lockdep_tasklist_lock_is_held());
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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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EXPORT_SYMBOL(pid_task);
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/*
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* Must be called under rcu_read_lock().
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*/
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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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RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
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"find_task_by_pid_ns() needs rcu_read_lock() protection");
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return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
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}
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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_ns(vnr, task_active_pid_ns(current));
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}
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struct pid *get_task_pid(struct task_struct *task, enum pid_type type)
|
|
{
|
|
struct pid *pid;
|
|
rcu_read_lock();
|
|
if (type != PIDTYPE_PID)
|
|
task = task->group_leader;
|
|
pid = get_pid(rcu_dereference(task->pids[type].pid));
|
|
rcu_read_unlock();
|
|
return pid;
|
|
}
|
|
EXPORT_SYMBOL_GPL(get_task_pid);
|
|
|
|
struct task_struct *get_pid_task(struct pid *pid, enum pid_type type)
|
|
{
|
|
struct task_struct *result;
|
|
rcu_read_lock();
|
|
result = pid_task(pid, type);
|
|
if (result)
|
|
get_task_struct(result);
|
|
rcu_read_unlock();
|
|
return result;
|
|
}
|
|
EXPORT_SYMBOL_GPL(get_pid_task);
|
|
|
|
struct pid *find_get_pid(pid_t nr)
|
|
{
|
|
struct pid *pid;
|
|
|
|
rcu_read_lock();
|
|
pid = get_pid(find_vpid(nr));
|
|
rcu_read_unlock();
|
|
|
|
return pid;
|
|
}
|
|
EXPORT_SYMBOL_GPL(find_get_pid);
|
|
|
|
pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns)
|
|
{
|
|
struct upid *upid;
|
|
pid_t nr = 0;
|
|
|
|
if (pid && ns->level <= pid->level) {
|
|
upid = &pid->numbers[ns->level];
|
|
if (upid->ns == ns)
|
|
nr = upid->nr;
|
|
}
|
|
return nr;
|
|
}
|
|
EXPORT_SYMBOL_GPL(pid_nr_ns);
|
|
|
|
pid_t pid_vnr(struct pid *pid)
|
|
{
|
|
return pid_nr_ns(pid, task_active_pid_ns(current));
|
|
}
|
|
EXPORT_SYMBOL_GPL(pid_vnr);
|
|
|
|
pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
|
|
struct pid_namespace *ns)
|
|
{
|
|
pid_t nr = 0;
|
|
|
|
rcu_read_lock();
|
|
if (!ns)
|
|
ns = task_active_pid_ns(current);
|
|
if (likely(pid_alive(task))) {
|
|
if (type != PIDTYPE_PID)
|
|
task = task->group_leader;
|
|
nr = pid_nr_ns(rcu_dereference(task->pids[type].pid), ns);
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
return nr;
|
|
}
|
|
EXPORT_SYMBOL(__task_pid_nr_ns);
|
|
|
|
pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
|
|
{
|
|
return pid_nr_ns(task_tgid(tsk), ns);
|
|
}
|
|
EXPORT_SYMBOL(task_tgid_nr_ns);
|
|
|
|
struct pid_namespace *task_active_pid_ns(struct task_struct *tsk)
|
|
{
|
|
return ns_of_pid(task_pid(tsk));
|
|
}
|
|
EXPORT_SYMBOL_GPL(task_active_pid_ns);
|
|
|
|
/*
|
|
* Used by proc to find the first pid that is greater than or equal to nr.
|
|
*
|
|
* If there is a pid at nr this function is exactly the same as find_pid_ns.
|
|
*/
|
|
struct pid *find_ge_pid(int nr, struct pid_namespace *ns)
|
|
{
|
|
struct pid *pid;
|
|
|
|
do {
|
|
pid = find_pid_ns(nr, ns);
|
|
if (pid)
|
|
break;
|
|
nr = next_pidmap(ns, nr);
|
|
} while (nr > 0);
|
|
|
|
return pid;
|
|
}
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
unsigned int i, pidhash_size;
|
|
|
|
pid_hash = alloc_large_system_hash("PID", sizeof(*pid_hash), 0, 18,
|
|
HASH_EARLY | HASH_SMALL,
|
|
&pidhash_shift, NULL,
|
|
0, 4096);
|
|
pidhash_size = 1U << pidhash_shift;
|
|
|
|
for (i = 0; i < pidhash_size; i++)
|
|
INIT_HLIST_HEAD(&pid_hash[i]);
|
|
}
|
|
|
|
void __init pidmap_init(void)
|
|
{
|
|
/* Verify no one has done anything silly: */
|
|
BUILD_BUG_ON(PID_MAX_LIMIT >= PIDNS_HASH_ADDING);
|
|
|
|
/* bump default and minimum pid_max based on number of cpus */
|
|
pid_max = min(pid_max_max, max_t(int, pid_max,
|
|
PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
|
|
pid_max_min = max_t(int, pid_max_min,
|
|
PIDS_PER_CPU_MIN * num_possible_cpus());
|
|
pr_info("pid_max: default: %u minimum: %u\n", pid_max, pid_max_min);
|
|
|
|
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 = KMEM_CACHE(pid,
|
|
SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT);
|
|
}
|