[PATCH 9/16] Make proc_flust_task to flush entries from multiple proc trees

[Pavel Emelianov <xemul@openvz.org>]

Since a task will appear in more than one proc tree we need to shrink many
trees. For this case we pass the struct pid to proc_flush_task() and shrink
the mounts of all the namespaces this pid belongs to.

The NULL passed to it means that only global mount is to be flushed.

Signed-off-by: Pavel Emelianov <xemul@openvz.org>

---

 fs/proc/base.c          |   25 ++++++++++++++++++++++---
 include/linux/proc_fs.h |    6 ++++--
 kernel/exit.c           |   18 +++++++++++++++++-
 3 files changed, 43 insertions(+), 6 deletions(-)

diff -upr linux-2.6.22-rc4-mm2.orig/fs/proc/base.c linux-2.6.22-rc4-mm2-2/fs/proc/base.c
--- linux-2.6.22-rc4-mm2.orig/fs/proc/base.c	2007-06-14 12:14:29.000000000 +0400
+++ linux-2.6.22-rc4-mm2-2/fs/proc/base.c	2007-07-04 19:00:38.000000000 +0400
@@ -75,6 +75,7 @@
 #include <linux/nsproxy.h>
 #include <linux/oom.h>
 #include <linux/elf.h>
+#include <linux/pid_namespace.h>
 #include "internal.h"
 
 /* NOTE:
@@ -2183,7 +2184,7 @@ static const struct inode_operations pro
  *       that no dcache entries will exist at process exit time it
  *       just makes it very unlikely that any will persist.
  */
-void proc_flush_task(struct task_struct *task)
+static void proc_flush_task_mnt(struct task_struct *task, struct vfsmount *mnt)
 {
 	struct dentry *dentry, *leader, *dir;
 	char buf[PROC_NUMBUF];
@@ -2191,7 +2192,7 @@ void proc_flush_task(struct task_struct 
 
 	name.name = buf;
 	name.len = snprintf(buf, sizeof(buf), "%d", task->pid);
-	dentry = d_hash_and_lookup(proc_mnt->mnt_root, &name);
+	dentry = d_hash_and_lookup(mnt->mnt_root, &name);
 	if (dentry) {
 		shrink_dcache_parent(dentry);
 		d_drop(dentry);
@@ -2203,7 +2204,7 @@ void proc_flush_task(struct task_struct 
 
 	name.name = buf;
 	name.len = snprintf(buf, sizeof(buf), "%d", task->tgid);
-	leader = d_hash_and_lookup(proc_mnt->mnt_root, &name);
+	leader = d_hash_and_lookup(mnt->mnt_root, &name);
 	if (!leader)
 		goto out;
 
@@ -2229,6 +2230,24 @@ out:
 	return;
 }
 
+/*
+ * when flushing dentries from proc one need to flush them from global
+ * proc (proc_mnt) and from all the namespaces' procs this task was seen
+ * in. this call is supposed to make all this job.
+ */
+
+void proc_flush_task(struct task_struct *task, struct pid *pid)
+{
+	int i;
+
+	proc_flush_task_mnt(task, proc_mnt);
+	if (pid == NULL)
+		return;
+
+	for (i = 1; i <= pid->level; i++)
+		proc_flush_task_mnt(task, pid->numbers[i].ns->proc_mnt);
+}
+
 static struct dentry *proc_pid_instantiate(struct inode *dir,
 					   struct dentry * dentry,
 					   struct task_struct *task, const void *ptr)
diff -upr linux-2.6.22-rc4-mm2.orig/include/linux/proc_fs.h linux-2.6.22-rc4-mm2-2/include/linux/proc_fs.h
--- linux-2.6.22-rc4-mm2.orig/include/linux/proc_fs.h	2007-06-14 12:14:29.000000000 +0400
+++ linux-2.6.22-rc4-mm2-2/include/linux/proc_fs.h	2007-07-04 19:00:38.000000000 +0400
@@ -111,7 +111,7 @@ extern void proc_misc_init(void);
 
 struct mm_struct;
 
-void proc_flush_task(struct task_struct *task);
+void proc_flush_task(struct task_struct *task, struct pid *pid);
 struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, struct nameidata *);
 int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir);
 unsigned long task_vsize(struct mm_struct *);
@@ -223,7 +227,9 @@ static inline void proc_net_remove(const
 #define proc_net_create(name, mode, info)	({ (void)(mode), NULL; })
 static inline void proc_net_remove(const char *name) {}
 
-static inline void proc_flush_task(struct task_struct *task) { }
+static inline void proc_flush_task(struct task_struct *task, struct pid *pid)
+{
+}
 
 static inline struct proc_dir_entry *create_proc_entry(const char *name,
 	mode_t mode, struct proc_dir_entry *parent) { return NULL; }
diff -upr linux-2.6.22-rc4-mm2.orig/kernel/exit.c linux-2.6.22-rc4-mm2-2/kernel/exit.c
--- linux-2.6.22-rc4-mm2.orig/kernel/exit.c	2007-07-04 19:00:38.000000000 +0400
+++ linux-2.6.22-rc4-mm2-2/kernel/exit.c	2007-07-04 19:00:38.000000000 +0400
@@ -154,6 +154,7 @@ static void delayed_put_task_struct(stru
 
 void release_task(struct task_struct * p)
 {
+	struct pid *pid;
 	struct task_struct *leader;
 	int zap_leader;
 repeat:
@@ -161,6 +162,20 @@ repeat:
 	write_lock_irq(&tasklist_lock);
 	ptrace_unlink(p);
 	BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
+	/*
+	 * we have to keep this pid till proc_flush_task() to make
+	 * it possible to flush all dentries holding it. pid will
+	 * be put ibidem
+	 *
+	 * however if the pid belogs to init namespace only, we can
+	 * optimize this out
+	 */
+	pid = task_pid(p);
+	if (!pid_ns_accessible(&init_pid_ns, pid))
+		get_pid(pid);
+	else
+		pid = NULL;
+
 	__exit_signal(p);
 
 	/*
@@ -185,7 +200,8 @@ repeat:
 	}
 
 	write_unlock_irq(&tasklist_lock);
-	proc_flush_task(p);
+	proc_flush_task(p, pid);
+	put_pid(pid);
 	release_thread(p);
 	call_rcu(&p->rcu, delayed_put_task_struct);