[PATCH] Define struct pspace

Define a per-container pid space object.  And create one instance of this
object, init_pspace, to define the entire pid space.  Subsequent patches
will provide/use interfaces to create/destroy pid spaces.

Its a subset/rework of Eric Biederman's patch
http://lkml.org/lkml/2006/2/6/285 .

Signed-off-by: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Kirill Korotaev <dev@sw.ru>
Cc: Andrey Savochkin <saw@sw.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 40 insertions, 24 deletions

diff --git a/fs/proc/proc_misc.c b/fs/proc/proc_misc.c
index 66bc425f2f3d..8d88e58ed5cc 100644
--- a/fs/proc/proc_misc.c
+++ b/fs/proc/proc_misc.c
@@ -45,6 +45,7 @@
 #include <linux/sysrq.h>
 #include <linux/vmalloc.h>
 #include <linux/crash_dump.h>
+#include <linux/pspace.h>
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
 #include <asm/io.h>
@@ -91,7 +92,7 @@ static int loadavg_read_proc(char *page, char **start, off_t off,
                 LOAD_INT(a), LOAD_FRAC(a),
                 LOAD_INT(b), LOAD_FRAC(b),
                 LOAD_INT(c), LOAD_FRAC(c),
-                nr_running(), nr_threads, last_pid);
+                nr_running(), nr_threads, init_pspace.last_pid);
         return proc_calc_metrics(page, start, off, count, eof, len);
 }
 
diff --git a/include/linux/pspace.h b/include/linux/pspace.h
index a8a064b0ad18..91d48b8b2d99 100644
--- a/include/linux/pspace.h
+++ b/include/linux/pspace.h
@@ -13,4 +13,11 @@ struct pidmap {
 
 #define PIDMAP_ENTRIES         ((PID_MAX_LIMIT + 8*PAGE_SIZE - 1)/PAGE_SIZE/8)
 
+struct pspace {
+       struct pidmap pidmap[PIDMAP_ENTRIES];
+       int last_pid;
+};
+
+extern struct pspace init_pspace;
+
 #endif /* _LINUX_PSPACE_H */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index dd6c2164e4a4..3b7c99265ace 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -118,7 +118,6 @@ extern unsigned long avenrun[];		/* Load averages */
 
 extern unsigned long total_forks;
 extern int nr_threads;
-extern int last_pid;
 DECLARE_PER_CPU(unsigned long, process_counts);
 extern int nr_processes(void);
 extern unsigned long nr_running(void);
diff --git a/kernel/pid.c b/kernel/pid.c
index 8234bd08a3cb..89107b7481af 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -34,7 +34,6 @@ static int pidhash_shift;
 static kmem_cache_t *pid_cachep;
 
 int pid_max = PID_MAX_DEFAULT;
-int last_pid;
 
 #define RESERVED_PIDS           300
 
@@ -43,7 +42,12 @@ int pid_max_max = PID_MAX_LIMIT;
 
 #define BITS_PER_PAGE           (PAGE_SIZE*8)
 #define BITS_PER_PAGE_MASK      (BITS_PER_PAGE-1)
-#define mk_pid(map, off)        (((map) - pidmap_array)*BITS_PER_PAGE + (off))
+
+static inline int mk_pid(struct pspace *pspace, struct pidmap *map, int off)
+{
+        return (map - pspace->pidmap)*BITS_PER_PAGE + off;
+}
+
 #define find_next_offset(map, off)                                      \
                 find_next_zero_bit((map)->page, BITS_PER_PAGE, off)
 
@@ -53,8 +57,12 @@ int pid_max_max = PID_MAX_LIMIT;
  * value does not cause lots of bitmaps to be allocated, but
  * the scheme scales to up to 4 million PIDs, runtime.
  */
-static struct pidmap pidmap_array[PIDMAP_ENTRIES] =
-         { [ 0 ... PIDMAP_ENTRIES-1 ] = { ATOMIC_INIT(BITS_PER_PAGE), NULL } };
+struct pspace init_pspace = {
+        .pidmap = {
+                [ 0 ... PIDMAP_ENTRIES-1] = { ATOMIC_INIT(BITS_PER_PAGE), NULL }
+        },
+        .last_pid = 0
+};
 
 /*
  * Note: disable interrupts while the pidmap_lock is held as an
@@ -69,40 +77,41 @@ static struct pidmap pidmap_array[PIDMAP_ENTRIES] =
  * irq handlers that take it we can leave the interrupts enabled.
  * For now it is easier to be safe than to prove it can't happen.
  */
+
 static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(pidmap_lock);
 
-static fastcall void free_pidmap(int pid)
+static fastcall void free_pidmap(struct pspace *pspace, int pid)
 {
-        struct pidmap *map = pidmap_array + pid / BITS_PER_PAGE;
+        struct pidmap *map = pspace->pidmap + pid / BITS_PER_PAGE;
         int offset = pid & BITS_PER_PAGE_MASK;
 
         clear_bit(offset, map->page);
         atomic_inc(&map->nr_free);
 }
 
-static int alloc_pidmap(void)
+static int alloc_pidmap(struct pspace *pspace)
 {
-        int i, offset, max_scan, pid, last = last_pid;
+        int i, offset, max_scan, pid, last = pspace->last_pid;
         struct pidmap *map;
 
         pid = last + 1;
         if (pid >= pid_max)
                 pid = RESERVED_PIDS;
         offset = pid & BITS_PER_PAGE_MASK;
-        map = &pidmap_array[pid/BITS_PER_PAGE];
+        map = &pspace->pidmap[pid/BITS_PER_PAGE];
         max_scan = (pid_max + BITS_PER_PAGE - 1)/BITS_PER_PAGE - !offset;
         for (i = 0; i <= max_scan; ++i) {
                 if (unlikely(!map->page)) {
-                        unsigned long page = get_zeroed_page(GFP_KERNEL);
+                        void *page = kzalloc(PAGE_SIZE, GFP_KERNEL);
                         /*
                          * Free the page if someone raced with us
                          * installing it:
                          */
                         spin_lock_irq(&pidmap_lock);
                         if (map->page)
-                                free_page(page);
+                                kfree(page);
                         else
-                                map->page = (void *)page;
+                                map->page = page;
                         spin_unlock_irq(&pidmap_lock);
                         if (unlikely(!map->page))
                                 break;
@@ -111,11 +120,11 @@ static int alloc_pidmap(void)
                         do {
                                 if (!test_and_set_bit(offset, map->page)) {
                                         atomic_dec(&map->nr_free);
-                                        last_pid = pid;
+                                        pspace->last_pid = pid;
                                         return pid;
                                 }
                                 offset = find_next_offset(map, offset);
-                                pid = mk_pid(map, offset);
+                                pid = mk_pid(pspace, map, offset);
                         /*
                          * find_next_offset() found a bit, the pid from it
                          * is in-bounds, and if we fell back to the last
@@ -126,16 +135,16 @@ static int alloc_pidmap(void)
                                         (i != max_scan || pid < last ||
                                             !((last+1) & BITS_PER_PAGE_MASK)));
                 }
-                if (map < &pidmap_array[(pid_max-1)/BITS_PER_PAGE]) {
+                if (map < &pspace->pidmap[(pid_max-1)/BITS_PER_PAGE]) {
                         ++map;
                         offset = 0;
                 } else {
-                        map = &pidmap_array[0];
+                        map = &pspace->pidmap[0];
                         offset = RESERVED_PIDS;
                         if (unlikely(last == offset))
                                 break;
                 }
-                pid = mk_pid(map, offset);
+                pid = mk_pid(pspace, map, offset);
         }
         return -1;
 }
@@ -182,7 +191,7 @@ fastcall void free_pid(struct pid *pid)
         hlist_del_rcu(&pid->pid_chain);
         spin_unlock_irqrestore(&pidmap_lock, flags);
 
-        free_pidmap(pid->nr);
+        free_pidmap(&init_pspace, pid->nr);
         call_rcu(&pid->rcu, delayed_put_pid);
 }
 
@@ -196,7 +205,7 @@ struct pid *alloc_pid(void)
         if (!pid)
                 goto out;
 
-        nr = alloc_pidmap();
+        nr = alloc_pidmap(&init_pspace);
         if (nr < 0)
                 goto out_free;
 
@@ -363,10 +372,10 @@ void __init pidhash_init(void)
 
 void __init pidmap_init(void)
 {
-        pidmap_array->page = (void *)get_zeroed_page(GFP_KERNEL);
+        init_pspace.pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
         /* Reserve PID 0. We never call free_pidmap(0) */
-        set_bit(0, pidmap_array->page);
-        atomic_dec(&pidmap_array->nr_free);
+        set_bit(0, init_pspace.pidmap[0].page);
+        atomic_dec(&init_pspace.pidmap[0].nr_free);
 
         pid_cachep = kmem_cache_create("pid", sizeof(struct pid),
                                         __alignof__(struct pid),