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Subject[PATCH 2/7] proc: Implement support for automounts in task directories

This is a genearl mechanism that is capable of removing
any unused mounts on /proc in any directory. As we flush
the mounts when a processes dies this mechanism is tailored
for flushing mounts in the per task and per task group
directories.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
fs/proc/Makefile | 1 +
fs/proc/automount.c | 29 +++++++++++++++++++++++++++++
fs/proc/internal.h | 3 +++
include/linux/proc_fs.h | 1 +
kernel/exit.c | 1 +
5 files changed, 35 insertions(+), 0 deletions(-)
create mode 100644 fs/proc/automount.c
diff --git a/fs/proc/Makefile b/fs/proc/Makefile
index 63d9651..862a8fe 100644
--- a/fs/proc/Makefile
+++ b/fs/proc/Makefile
@@ -18,6 +18,7 @@ proc-y += meminfo.o
proc-y += stat.o
proc-y += uptime.o
proc-y += version.o
+proc-y += automount.o
proc-$(CONFIG_PROC_SYSCTL) += proc_sysctl.o
proc-$(CONFIG_NET) += proc_net.o
proc-$(CONFIG_PROC_KCORE) += kcore.o
diff --git a/fs/proc/automount.c b/fs/proc/automount.c
new file mode 100644
index 0000000..a1fabf2
--- /dev/null
+++ b/fs/proc/automount.c
@@ -0,0 +1,29 @@
+#include <linux/workqueue.h>
+#include <linux/mount.h>
+#include <linux/vfs.h>
+#include "internal.h"
+
+LIST_HEAD(proc_automounts);
+
+static void proc_expire_automounts(struct work_struct *work);
+
+static DECLARE_DELAYED_WORK(proc_automount_task, proc_expire_automounts);
+static int proc_automount_timeout = 500 * HZ;
+
+void proc_shrink_automounts(void)
+{
+ struct list_head *list = &proc_automounts;
+
+ mark_mounts_for_expiry(list);
+ mark_mounts_for_expiry(list);
+ if (list_empty(list))
+ return;
+
+ schedule_delayed_work(&proc_automount_task, proc_automount_timeout);
+}
+
+static void proc_expire_automounts(struct work_struct *work)
+{
+ proc_shrink_automounts();
+}
+
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 3e8aeb8..2a8eabb 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -93,3 +93,6 @@ struct pde_opener {
int (*release)(struct inode *, struct file *);
struct list_head lh;
};
+
+extern struct list_head proc_automounts;
+
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index b8bdb96..3505a72 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -101,6 +101,7 @@ extern spinlock_t proc_subdir_lock;

extern void proc_root_init(void);

+void proc_shrink_automounts(void);
void proc_flush_task(struct task_struct *task);
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);
diff --git a/kernel/exit.c b/kernel/exit.c
index 80137a5..8a8badb 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -161,6 +161,7 @@ void release_task(struct task_struct * p)
repeat:
tracehook_prepare_release_task(p);
atomic_dec(&p->user->processes);
+ proc_shrink_automounts();
proc_flush_task(p);
write_lock_irq(&tasklist_lock);
tracehook_finish_release_task(p);
--
1.5.3.rc6.17.g1911


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