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![Pavel Tatashin](/assets/img/avatar_default.png)
Update dcache, inode, pid, mountpoint, and mount hash tables to use HASH_ZERO, and remove initialization after allocations. In case of places where HASH_EARLY was used such as in __pv_init_lock_hash the zeroed hash table was already assumed, because memblock zeroes the memory. CPU: SPARC M6, Memory: 7T Before fix: Dentry cache hash table entries: 1073741824 Inode-cache hash table entries: 536870912 Mount-cache hash table entries: 16777216 Mountpoint-cache hash table entries: 16777216 ftrace: allocating 20414 entries in 40 pages Total time: 11.798s After fix: Dentry cache hash table entries: 1073741824 Inode-cache hash table entries: 536870912 Mount-cache hash table entries: 16777216 Mountpoint-cache hash table entries: 16777216 ftrace: allocating 20414 entries in 40 pages Total time: 3.198s CPU: Intel Xeon E5-2630, Memory: 2.2T: Before fix: Dentry cache hash table entries: 536870912 Inode-cache hash table entries: 268435456 Mount-cache hash table entries: 8388608 Mountpoint-cache hash table entries: 8388608 CPU: Physical Processor ID: 0 Total time: 3.245s After fix: Dentry cache hash table entries: 536870912 Inode-cache hash table entries: 268435456 Mount-cache hash table entries: 8388608 Mountpoint-cache hash table entries: 8388608 CPU: Physical Processor ID: 0 Total time: 3.244s Link: http://lkml.kernel.org/r/1488432825-92126-4-git-send-email-pasha.tatashin@oracle.com Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com> Reviewed-by: Babu Moger <babu.moger@oracle.com> Cc: David Miller <davem@davemloft.net> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
606 lines
15 KiB
C
606 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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#include <linux/sched/task.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 = KREF_INIT(2),
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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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disable_pid_allocation(ns);
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goto out_free;
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}
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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)
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{
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struct pid *pid;
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rcu_read_lock();
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if (type != PIDTYPE_PID)
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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 pidhash_size;
|
|
|
|
pid_hash = alloc_large_system_hash("PID", sizeof(*pid_hash), 0, 18,
|
|
HASH_EARLY | HASH_SMALL | HASH_ZERO,
|
|
&pidhash_shift, NULL,
|
|
0, 4096);
|
|
pidhash_size = 1U << pidhash_shift;
|
|
}
|
|
|
|
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);
|
|
}
|