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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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