[PATCH] (3/5) sane procfs/dcache interaction

 - sane dentry retention.  Namely, we don't kill /proc/<pid> dentries at the
   first opportunity (as the current tree does).  Instead we do the following:
	* ->d_delete() kills it only if process is already dead.
	* all ->lookup() in proc/base.c end with checking if process is still
	  alive and unhash if it isn't.
	* proc_pid_lookup() (lookup for /proc/<pid>) caches reference to dentry
	  in task_struct.  It's _not_ counted in ->d_count.
	* ->d_iput() resets said reference to NULL.
	* release_task() (burying a zombie) checks if there is a cached
	  reference and if there is - shrinks the subtree.
	* tasklist_lock is used for exclusion.
   That way we are guaranteed that after release_task() all dentries in
   /proc/<pid> will go away as soon as possible; OTOH, before release_task()
   we have normal retention policy - they go away under memory pressure with
   the same rules as for dentries on any other fs.

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8f0df64bb723..a65b376d99da 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -346,6 +346,7 @@ struct task_struct {
 
 /* journalling filesystem info */
 	void *journal_info;
+	struct dentry *proc_dentry;
 };
 
 extern void __put_task_struct(struct task_struct *tsk);