bsdacct: switch from global bsd_acct_struct instance to per-pidns one

Allocate the structure on the first call to sys_acct().  After this each
namespace, that ordered the accounting, will live with this structure till
its own death.

Two notes
- routines, that close the accounting on fs umount time use
  the init_pid_ns's acct by now;
- accounting routine accounts to dying task's namespace
  (also by now).

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 71 insertions, 18 deletions

diff --git a/include/linux/acct.h b/include/linux/acct.h
index e8cae54e8d88..882dc7248766 100644
--- a/include/linux/acct.h
+++ b/include/linux/acct.h
@@ -120,17 +120,20 @@ struct acct_v3
 struct vfsmount;
 struct super_block;
 struct pacct_struct;
+struct pid_namespace;
 extern void acct_auto_close_mnt(struct vfsmount *m);
 extern void acct_auto_close(struct super_block *sb);
 extern void acct_init_pacct(struct pacct_struct *pacct);
 extern void acct_collect(long exitcode, int group_dead);
 extern void acct_process(void);
+extern void acct_exit_ns(struct pid_namespace *);
 #else
 #define acct_auto_close_mnt(x)  do { } while (0)
 #define acct_auto_close(x)      do { } while (0)
 #define acct_init_pacct(x)      do { } while (0)
 #define acct_collect(x,y)       do { } while (0)
 #define acct_process()          do { } while (0)
+#define acct_exit_ns(ns)        do { } while (0)
 #endif
 
 /*
diff --git a/kernel/acct.c b/kernel/acct.c
index 72d4760c8da8..febbbc67157e 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -93,8 +93,6 @@ struct bsd_acct_struct {
 
 static DEFINE_SPINLOCK(acct_lock);
 
-static struct bsd_acct_struct acct_globals __cacheline_aligned;
-
 /*
  * Called whenever the timer says to check the free space.
  */
@@ -176,7 +174,8 @@ out:
  *
  * NOTE: acct_lock MUST be held on entry and exit.
  */
-static void acct_file_reopen(struct bsd_acct_struct *acct, struct file *file)
+static void acct_file_reopen(struct bsd_acct_struct *acct, struct file *file,
+                struct pid_namespace *ns)
 {
         struct file *old_acct = NULL;
         struct pid_namespace *old_ns = NULL;
@@ -188,10 +187,11 @@ static void acct_file_reopen(struct bsd_acct_struct *acct, struct file *file)
                 acct->active = 0;
                 acct->needcheck = 0;
                 acct->file = NULL;
+                acct->ns = NULL;
         }
         if (file) {
                 acct->file = file;
-                acct->ns = get_pid_ns(task_active_pid_ns(current));
+                acct->ns = ns;
                 acct->needcheck = 0;
                 acct->active = 1;
                 /* It's been deleted if it was used before so this is safe */
@@ -204,7 +204,6 @@ static void acct_file_reopen(struct bsd_acct_struct *acct, struct file *file)
                 spin_unlock(&acct_lock);
                 do_acct_process(acct, old_ns, old_acct);
                 filp_close(old_acct, NULL);
-                put_pid_ns(old_ns);
                 spin_lock(&acct_lock);
         }
 }
@@ -213,6 +212,8 @@ static int acct_on(char *name)
 {
         struct file *file;
         int error;
+        struct pid_namespace *ns;
+        struct bsd_acct_struct *acct = NULL;
 
         /* Difference from BSD - they don't do O_APPEND */
         file = filp_open(name, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
@@ -229,18 +230,34 @@ static int acct_on(char *name)
                 return -EIO;
         }
 
+        ns = task_active_pid_ns(current);
+        if (ns->bacct == NULL) {
+                acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
+                if (acct == NULL) {
+                        filp_close(file, NULL);
+                        return -ENOMEM;
+                }
+        }
+
         error = security_acct(file);
         if (error) {
+                kfree(acct);
                 filp_close(file, NULL);
                 return error;
         }
 
         spin_lock(&acct_lock);
+        if (ns->bacct == NULL) {
+                ns->bacct = acct;
+                acct = NULL;
+        }
+
         mnt_pin(file->f_path.mnt);
-        acct_file_reopen(&acct_globals, file);
+        acct_file_reopen(ns->bacct, file, ns);
         spin_unlock(&acct_lock);
 
         mntput(file->f_path.mnt); /* it's pinned, now give up active reference */
+        kfree(acct);
 
         return 0;
 }
@@ -270,10 +287,16 @@ asmlinkage long sys_acct(const char __user *name)
                 error = acct_on(tmp);
                 putname(tmp);
         } else {
+                struct bsd_acct_struct *acct;
+
+                acct = task_active_pid_ns(current)->bacct;
+                if (acct == NULL)
+                        return 0;
+
                 error = security_acct(NULL);
                 if (!error) {
                         spin_lock(&acct_lock);
-                        acct_file_reopen(&acct_globals, NULL);
+                        acct_file_reopen(acct, NULL, NULL);
                         spin_unlock(&acct_lock);
                 }
         }
@@ -289,9 +312,15 @@ asmlinkage long sys_acct(const char __user *name)
  */
 void acct_auto_close_mnt(struct vfsmount *m)
 {
+        struct bsd_acct_struct *acct;
+
+        acct = init_pid_ns.bacct;
+        if (acct == NULL)
+                return;
+
         spin_lock(&acct_lock);
-        if (acct_globals.file && acct_globals.file->f_path.mnt == m)
-                acct_file_reopen(&acct_globals, NULL);
+        if (acct->file && acct->file->f_path.mnt == m)
+                acct_file_reopen(acct, NULL, NULL);
         spin_unlock(&acct_lock);
 }
 
@@ -304,10 +333,29 @@ void acct_auto_close_mnt(struct vfsmount *m)
  */
 void acct_auto_close(struct super_block *sb)
 {
+        struct bsd_acct_struct *acct;
+
+        acct = init_pid_ns.bacct;
+        if (acct == NULL)
+                return;
+
         spin_lock(&acct_lock);
-        if (acct_globals.file &&
-            acct_globals.file->f_path.mnt->mnt_sb == sb) {
-                acct_file_reopen(&acct_globals, NULL);
+        if (acct->file && acct->file->f_path.mnt->mnt_sb == sb)
+                acct_file_reopen(acct, NULL, NULL);
+        spin_unlock(&acct_lock);
+}
+
+void acct_exit_ns(struct pid_namespace *ns)
+{
+        struct bsd_acct_struct *acct;
+
+        spin_lock(&acct_lock);
+        acct = ns->bacct;
+        if (acct != NULL) {
+                if (acct->file != NULL)
+                        acct_file_reopen(acct, NULL, NULL);
+
+                kfree(acct);
         }
         spin_unlock(&acct_lock);
 }
@@ -587,25 +635,25 @@ void acct_collect(long exitcode, int group_dead)
 void acct_process(void)
 {
         struct file *file = NULL;
-        struct pid_namespace *ns;
+        struct pid_namespace *ns = task_active_pid_ns(current);
+        struct bsd_acct_struct *acct;
 
+        acct = ns->bacct;
         /*
          * accelerate the common fastpath:
          */
-        if (!acct_globals.file)
+        if (!acct || !acct->file)
                 return;
 
         spin_lock(&acct_lock);
-        file = acct_globals.file;
+        file = acct->file;
         if (unlikely(!file)) {
                 spin_unlock(&acct_lock);
                 return;
         }
         get_file(file);
-        ns = get_pid_ns(acct_globals.ns);
         spin_unlock(&acct_lock);
 
-        do_acct_process(&acct_globals, ns, file);
+        do_acct_process(acct, ns, file);
         fput(file);
-        put_pid_ns(ns);
 }
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 06331cc1c3f5..ea567b78d1aa 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -12,6 +12,7 @@
 #include <linux/pid_namespace.h>
 #include <linux/syscalls.h>
 #include <linux/err.h>
+#include <linux/acct.h>
 
 #define BITS_PER_PAGE           (PAGE_SIZE*8)
 
@@ -181,6 +182,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 
         /* Child reaper for the pid namespace is going away */
         pid_ns->child_reaper = NULL;
+        acct_exit_ns(pid_ns);
         return;
 }