pid: remove pidhash

pidhash is no longer required as all the information can be looked up
from idr tree.  nr_hashed represented the number of pids that had been
hashed.  Since, nr_hashed and PIDNS_HASH_ADDING are no longer relevant,
it has been renamed to pid_allocated and PIDNS_ADDING respectively.

[gs051095@gmail.com: v6]
Link: http://lkml.kernel.org/r/1507760379-21662-3-git-send-email-gs051095@gmail.com
Link: http://lkml.kernel.org/r/1507583624-22146-3-git-send-email-gs051095@gmail.com
Signed-off-by: Gargi Sharma <gs051095@gmail.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Tested-by: Tony Luck <tony.luck@intel.com>	[ia64]
Cc: Julia Lawall <julia.lawall@lip6.fr>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/ia64/kernel/asm-offsets.c b/arch/ia64/kernel/asm-offsets.c
index f7693f4..f4db216 100644 (file)
--- a/arch/ia64/kernel/asm-offsets.c
+++ b/arch/ia64/kernel/asm-offsets.c
@@ -31,8 +31,8 @@ void foo(void)
        DEFINE(SIGFRAME_SIZE, sizeof (struct sigframe));
        DEFINE(UNW_FRAME_INFO_SIZE, sizeof (struct unw_frame_info));
 
-       BUILD_BUG_ON(sizeof(struct upid) != 32);
-       DEFINE(IA64_UPID_SHIFT, 5);
+       BUILD_BUG_ON(sizeof(struct upid) != 16);
+       DEFINE(IA64_UPID_SHIFT, 4);
 
        BLANK();
 

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 8062e6c..6a53262 100644 (file)
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -105,7 +105,6 @@ extern struct group_info init_groups;
        .numbers        = { {                                           \
                .nr             = 0,                                    \
                .ns             = &init_pid_ns,                         \
-               .pid_chain      = { .next = NULL, .pprev = NULL },      \
        }, }                                                            \
 }
 

diff --git a/include/linux/pid.h b/include/linux/pid.h
index dfd684c..7633d55 100644 (file)
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -51,10 +51,8 @@ enum pid_type
  */
 
 struct upid {
-       /* Try to keep pid_chain in the same cacheline as nr for find_vpid */
        int nr;
        struct pid_namespace *ns;
-       struct hlist_node pid_chain;
 };
 
 struct pid

diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 92c6aa5..49538b1 100644 (file)
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -25,7 +25,7 @@ struct pid_namespace {
        struct kref kref;
        struct idr idr;
        struct rcu_head rcu;
-       unsigned int nr_hashed;
+       unsigned int pid_allocated;
        struct task_struct *child_reaper;
        struct kmem_cache *pid_cachep;
        unsigned int level;
@@ -49,7 +49,7 @@ struct pid_namespace {
 
 extern struct pid_namespace init_pid_ns;
 
-#define PIDNS_HASH_ADDING (1U << 31)
+#define PIDNS_ADDING (1U << 31)
 
 #ifdef CONFIG_PID_NS
 static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns)

diff --git a/init/main.c b/init/main.c
index d0cbcfc..dfec380 100644 (file)
--- a/init/main.c
+++ b/init/main.c
@@ -562,7 +562,6 @@ asmlinkage __visible void __init start_kernel(void)
         * kmem_cache_init()
         */
        setup_log_buf(0);
-       pidhash_init();
        vfs_caches_init_early();
        sort_main_extable();
        trap_init();

diff --git a/kernel/fork.c b/kernel/fork.c
index 4e55eed..432eadf 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1871,7 +1871,7 @@ static __latent_entropy struct task_struct *copy_process(
                retval = -ERESTARTNOINTR;
                goto bad_fork_cancel_cgroup;
        }
-       if (unlikely(!(ns_of_pid(pid)->nr_hashed & PIDNS_HASH_ADDING))) {
+       if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
                retval = -ENOMEM;
                goto bad_fork_cancel_cgroup;
        }

diff --git a/kernel/pid.c b/kernel/pid.c
index 0ce5936..b13b624 100644 (file)
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -41,10 +41,6 @@
 #include <linux/sched/task.h>
 #include <linux/idr.h>
 
-#define pid_hashfn(nr, ns)     \
-       hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift)
-static struct hlist_head *pid_hash;
-static unsigned int pidhash_shift = 4;
 struct pid init_struct_pid = INIT_STRUCT_PID;
 
 int pid_max = PID_MAX_DEFAULT;
@@ -54,7 +50,6 @@ int pid_max = PID_MAX_DEFAULT;
 int pid_max_min = RESERVED_PIDS + 1;
 int pid_max_max = PID_MAX_LIMIT;
 
-
 /*
  * PID-map pages start out as NULL, they get allocated upon
  * first use and are never deallocated. This way a low pid_max
@@ -64,7 +59,7 @@ int pid_max_max = PID_MAX_LIMIT;
 struct pid_namespace init_pid_ns = {
        .kref = KREF_INIT(2),
        .idr = IDR_INIT,
-       .nr_hashed = PIDNS_HASH_ADDING,
+       .pid_allocated = PIDNS_ADDING,
        .level = 0,
        .child_reaper = &init_task,
        .user_ns = &init_user_ns,
@@ -123,8 +118,7 @@ void free_pid(struct pid *pid)
        for (i = 0; i <= pid->level; i++) {
                struct upid *upid = pid->numbers + i;
                struct pid_namespace *ns = upid->ns;
-               hlist_del_rcu(&upid->pid_chain);
-               switch (--ns->nr_hashed) {
+               switch (--ns->pid_allocated) {
                case 2:
                case 1:
                        /* When all that is left in the pid namespace
@@ -133,10 +127,10 @@ void free_pid(struct pid *pid)
                         */
                        wake_up_process(ns->child_reaper);
                        break;
-               case PIDNS_HASH_ADDING:
+               case PIDNS_ADDING:
                        /* Handle a fork failure of the first process */
                        WARN_ON(ns->child_reaper);
-                       ns->nr_hashed = 0;
+                       ns->pid_allocated = 0;
                        /* fall through */
                case 0:
                        schedule_work(&ns->proc_work);
@@ -212,14 +206,12 @@ struct pid *alloc_pid(struct pid_namespace *ns)
 
        upid = pid->numbers + ns->level;
        spin_lock_irq(&pidmap_lock);
-       if (!(ns->nr_hashed & PIDNS_HASH_ADDING))
+       if (!(ns->pid_allocated & PIDNS_ADDING))
                goto out_unlock;
        for ( ; upid >= pid->numbers; --upid) {
-               hlist_add_head_rcu(&upid->pid_chain,
-                               &pid_hash[pid_hashfn(upid->nr, upid->ns)]);
                /* Make the PID visible to find_pid_ns. */
                idr_replace(&upid->ns->idr, pid, upid->nr);
-               upid->ns->nr_hashed++;
+               upid->ns->pid_allocated++;
        }
        spin_unlock_irq(&pidmap_lock);
 
@@ -243,21 +235,13 @@ out_free:
 void disable_pid_allocation(struct pid_namespace *ns)
 {
        spin_lock_irq(&pidmap_lock);
-       ns->nr_hashed &= ~PIDNS_HASH_ADDING;
+       ns->pid_allocated &= ~PIDNS_ADDING;
        spin_unlock_irq(&pidmap_lock);
 }
 
 struct pid *find_pid_ns(int nr, struct pid_namespace *ns)
 {
-       struct upid *pnr;
-
-       hlist_for_each_entry_rcu(pnr,
-                       &pid_hash[pid_hashfn(nr, ns)], pid_chain)
-               if (pnr->nr == nr && pnr->ns == ns)
-                       return container_of(pnr, struct pid,
-                                       numbers[ns->level]);
-
-       return NULL;
+       return idr_find(&ns->idr, nr);
 }
 EXPORT_SYMBOL_GPL(find_pid_ns);
 
@@ -413,6 +397,7 @@ pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
                if (type != PIDTYPE_PID) {
                        if (type == __PIDTYPE_TGID)
                                type = PIDTYPE_PID;
+
                        task = task->group_leader;
                }
                nr = pid_nr_ns(rcu_dereference(task->pids[type].pid), ns);
@@ -439,23 +424,10 @@ struct pid *find_ge_pid(int nr, struct pid_namespace *ns)
        return idr_get_next(&ns->idr, &nr);
 }
 
-/*
- * 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)
-{
-       pid_hash = alloc_large_system_hash("PID", sizeof(*pid_hash), 0, 18,
-                                          HASH_EARLY | HASH_SMALL | HASH_ZERO,
-                                          &pidhash_shift, NULL,
-                                          0, 4096);
-}
-
 void __init pid_idr_init(void)
 {
        /* Verify no one has done anything silly: */
-       BUILD_BUG_ON(PID_MAX_LIMIT >= PIDNS_HASH_ADDING);
+       BUILD_BUG_ON(PID_MAX_LIMIT >= PIDNS_ADDING);
 
        /* bump default and minimum pid_max based on number of cpus */
        pid_max = min(pid_max_max, max_t(int, pid_max,

diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index ca7c8a8..0b53eef 100644 (file)
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -133,7 +133,7 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns
        ns->parent = get_pid_ns(parent_pid_ns);
        ns->user_ns = get_user_ns(user_ns);
        ns->ucounts = ucounts;
-       ns->nr_hashed = PIDNS_HASH_ADDING;
+       ns->pid_allocated = PIDNS_ADDING;
        INIT_WORK(&ns->proc_work, proc_cleanup_work);
 
        return ns;
@@ -254,7 +254,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
         * sys_wait4() above can't reap the EXIT_DEAD children but we do not
         * really care, we could reparent them to the global init. We could
         * exit and reap ->child_reaper even if it is not the last thread in
-        * this pid_ns, free_pid(nr_hashed == 0) calls proc_cleanup_work(),
+        * this pid_ns, free_pid(pid_allocated == 0) calls proc_cleanup_work(),
         * pid_ns can not go away until proc_kill_sb() drops the reference.
         *
         * But this ns can also have other tasks injected by setns()+fork().
@@ -268,7 +268,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
         */
        for (;;) {
                set_current_state(TASK_INTERRUPTIBLE);
-               if (pid_ns->nr_hashed == init_pids)
+               if (pid_ns->pid_allocated == init_pids)
                        break;
                schedule();
        }