[PATCH] proc: Rewrite the proc dentry flush on exit optimization

To keep the dcache from filling up with dead /proc entries we flush them on
process exit.  However over the years that code has gotten hairy with a
dentry_pointer and a lock in task_struct and misdocumented as a correctness
feature.

I have rewritten this code to look and see if we have a corresponding entry in
the dcache and if so flush it on process exit.  This removes the extra fields
in the task_struct and allows me to trivially handle the case of a
/proc/<tgid>/task/<pid> entry as well as the current /proc/<pid> entries.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 2 insertions, 8 deletions

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 41ecbb847f3..e127ef7e8da 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -119,7 +119,6 @@ extern struct group_info init_groups;
                 .signal = {{0}}},                                       \
         .blocked        = {{0}},                                        \
         .alloc_lock     = SPIN_LOCK_UNLOCKED,                           \
-        .proc_lock      = SPIN_LOCK_UNLOCKED,                           \
         .journal_info   = NULL,                                         \
         .cpu_timers     = INIT_CPU_TIMERS(tsk.cpu_timers),              \
         .fs_excl        = ATOMIC_INIT(0),                               \
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 9dd84884abb..d4d2081dbaf 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -99,9 +99,8 @@ extern void proc_misc_init(void);
 
 struct mm_struct;
 
+void proc_flush_task(struct task_struct *task);
 struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, struct nameidata *);
-struct dentry *proc_pid_unhash(struct task_struct *p);
-void proc_pid_flush(struct dentry *proc_dentry);
 int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir);
 unsigned long task_vsize(struct mm_struct *);
 int task_statm(struct mm_struct *, int *, int *, int *, int *);
@@ -211,8 +210,7 @@ static inline void proc_net_remove(const char *name)
 #define proc_net_create(name, mode, info)       ({ (void)(mode), NULL; })
 static inline void proc_net_remove(const char *name) {}
 
-static inline struct dentry *proc_pid_unhash(struct task_struct *p) { return NULL; }
-static inline void proc_pid_flush(struct dentry *proc_dentry) { }
+static inline void proc_flush_task(struct task_struct *task) { }
 
 static inline struct proc_dir_entry *create_proc_entry(const char *name,
         mode_t mode, struct proc_dir_entry *parent) { return NULL; }
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8d11d9310db..122a25c1b99 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -842,8 +842,6 @@ struct task_struct {
         u32 self_exec_id;
 /* Protection of (de-)allocation: mm, files, fs, tty, keyrings */
         spinlock_t alloc_lock;
-/* Protection of proc_dentry: nesting proc_lock, dcache_lock, write_lock_irq(&tasklist_lock); */
-        spinlock_t proc_lock;
 
 #ifdef CONFIG_DEBUG_MUTEXES
         /* mutex deadlock detection */
@@ -856,7 +854,6 @@ struct task_struct {
 /* VM state */
         struct reclaim_state *reclaim_state;
 
-        struct dentry *proc_dentry;
         struct backing_dev_info *backing_dev_info;
 
         struct io_context *io_context;