[Devel] [PATCH 4/6] c/r: introduce pids objects

[Oren Laadan]

Add the interface to handle pids as proper c/r shared objects.  This
is the first step in converting the c/r code to hanlde pid as pids
objects that are namespace aware. Also remote the unused field
@root_pid from struct ckpt_ctx.

Signed-off-by: Oren Laadan <orenl at cs.columbia.edu>
---
 include/linux/checkpoint_hdr.h   |    6 +++++-
 include/linux/checkpoint_types.h |    1 -
 kernel/checkpoint/checkpoint.c   |    2 --
 kernel/checkpoint/restart.c      |    1 -
 kernel/pid.c                     |   28 ++++++++++++++++++++++++++++
 5 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index b12d586..922eff0 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -245,6 +245,8 @@ struct ckpt_hdr_objref {
 enum obj_type {
 	CKPT_OBJ_IGNORE = 0,
 #define CKPT_OBJ_IGNORE CKPT_OBJ_IGNORE
+	CKPT_OBJ_PID,
+#define CKPT_OBJ_PID CKPT_OBJ_PID
 	CKPT_OBJ_INODE,
 #define CKPT_OBJ_INODE CKPT_OBJ_INODE
 	CKPT_OBJ_FILE_TABLE,
@@ -373,7 +375,9 @@ struct ckpt_pids {
 } __attribute__((aligned(8)));
 
 /* pids */
-#define CKPT_PID_NULL  -1
+/* (negative but not valid error) */
+#define CKPT_PID_NULL  (-4096)  /* null pid pointer */
+#define CKPT_PID_ROOT  (-4097)  /* pid same as root task */
 
 /* task data */
 struct ckpt_hdr_task {
diff --git a/include/linux/checkpoint_types.h b/include/linux/checkpoint_types.h
index cf74d3e..87a569a 100644
--- a/include/linux/checkpoint_types.h
+++ b/include/linux/checkpoint_types.h
@@ -35,7 +35,6 @@ struct ckpt_ctx {
 	ktime_t ktime_begin;		/* operation start time */
 
 	int root_init;				/* [container] root init ? */
-	pid_t root_pid;				/* [container] root pid */
 	struct task_struct *root_task;		/* [container] root task */
 	struct nsproxy *root_nsproxy;		/* [container] root nsproxy */
 	struct task_struct *root_freezer;	/* [container] root task */
diff --git a/kernel/checkpoint/checkpoint.c b/kernel/checkpoint/checkpoint.c
index 01653d7..a850423 100644
--- a/kernel/checkpoint/checkpoint.c
+++ b/kernel/checkpoint/checkpoint.c
@@ -628,8 +628,6 @@ static int init_checkpoint_ctx(struct ckpt_ctx *ctx, pid_t pid)
 	 * occurs then ckpt_ctx_free() is eventually called.
 	 */
 
-	ctx->root_pid = pid;
-
 	/* root task */
 	rcu_read_lock();
 	task = find_task_by_vpid(pid);
diff --git a/kernel/checkpoint/restart.c b/kernel/checkpoint/restart.c
index 66b6625..9aaab4f 100644
--- a/kernel/checkpoint/restart.c
+++ b/kernel/checkpoint/restart.c
@@ -1178,7 +1178,6 @@ static struct task_struct *choose_root_task(struct ckpt_ctx *ctx, pid_t pid)
 	struct task_struct *task;
 
 	if (ctx->uflags & RESTART_TASKSELF) {
-		ctx->root_pid = pid;
 		ctx->root_task = current;
 		get_task_struct(current);
 		return current;
diff --git a/kernel/pid.c b/kernel/pid.c
index f08f40a..0269991 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -36,6 +36,7 @@
 #include <linux/pid_namespace.h>
 #include <linux/init_task.h>
 #include <linux/syscalls.h>
+#include <linux/checkpoint.h>
 
 #define pid_hashfn(nr, ns)	\
 	hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift)
@@ -571,6 +572,30 @@ struct pid *find_ge_pid(int nr, struct pid_namespace *ns)
 	return pid;
 }
 
+#ifdef CONFIG_CHECKPOINT
+
+/* pid-related checkpoint objects */
+
+static int obj_pid_grab(void *ptr)
+{
+	get_pid((struct pid *) ptr);
+	return 0;
+}
+
+static void obj_pid_drop(void *ptr, int lastref)
+{
+	put_pid((struct pid *) ptr);
+}
+
+static const struct ckpt_obj_ops ckpt_obj_pid_ops = {
+	.obj_name = "PID",
+	.obj_type = CKPT_OBJ_PID,
+	.ref_drop = obj_pid_drop,
+	.ref_grab = obj_pid_grab,
+};
+
+#endif /* CONFIG_CHECKPOINT */
+
 /*
  * The pid hash table is scaled according to the amount of memory in the
  * machine.  From a minimum of 16 slots up to 4096 slots at one gigabyte or
@@ -605,4 +630,7 @@ void __init pidmap_init(void)
 
 	init_pid_ns.pid_cachep = KMEM_CACHE(pid,
 			SLAB_HWCACHE_ALIGN | SLAB_PANIC);
+#ifdef CONFIG_CHECKPOINT
+	register_checkpoint_obj(&ckpt_obj_pid_ops);
+#endif
 }
-- 
1.7.1

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