To ensure that a module does not unload in the middle of a checkpoint
or a restart operation, pin (module_get) all the modules during either
operation. For that, add a new memeber ->owner in ckpt_obj_ops.
Also add a counter that keeps track of how many module_gets we have
going on, to properly handle new modules that register when an
operation is underway.
This is a proof of concept, applies on top of the patch that introduces
objhash on rc7 (patch 33).
Todo:
- I put the initialization part in init_*_ctx(), but it could be moved
to ckpt_ctx_alloc() which is common to both checkpoint and restart.
- If this is ok, then additional patches should adjust those modules
that indeed register...
Signed-off-by: Oren Laadan <orenl@xxxxxxxxxxxxxxx>
---
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 2f5af3c..4ed8a8c 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -40,11 +40,13 @@ extern long do_sys_restart(pid_t pid, int fd,
#define CKPT_CTX_RESTART_BIT 1
#define CKPT_CTX_SUCCESS_BIT 2
#define CKPT_CTX_ERROR_BIT 3
+#define CKPT_CTX_PINNED_BIT 4
#define CKPT_CTX_CHECKPOINT (1 << CKPT_CTX_CHECKPOINT_BIT)
#define CKPT_CTX_RESTART (1 << CKPT_CTX_RESTART_BIT)
#define CKPT_CTX_SUCCESS (1 << CKPT_CTX_SUCCESS_BIT)
#define CKPT_CTX_ERROR (1 << CKPT_CTX_ERROR_BIT)
+#define CKPT_CTX_PINNED (1 << CKPT_CTX_PINNED_BIT)
/* ckpt_ctx: uflags */
#define CHECKPOINT_USER_FLAGS CHECKPOINT_SUBTREE
@@ -107,6 +109,9 @@ static inline int ckpt_get_error(struct ckpt_ctx *ctx)
extern void restore_notify_error(struct ckpt_ctx *ctx);
/* obj_hash */
+extern int ckpt_obj_module_get(void);
+extern void ckpt_obj_module_put(void);
+
extern void ckpt_obj_hash_free(struct ckpt_ctx *ctx);
extern int ckpt_obj_hash_alloc(struct ckpt_ctx *ctx);
@@ -284,6 +289,7 @@ extern void _ckpt_msg_complete(struct ckpt_ctx *ctx);
struct ckpt_obj_ops;
extern int register_checkpoint_obj(const struct ckpt_obj_ops *ops);
+extern void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops);
#else /* CONFIG_CHEKCPOINT */
@@ -293,6 +299,10 @@ static inline int register_checkpoint_obj(const struct ckpt_obj_ops *ops)
return 0;
}
+static inline void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops)
+{
+}
+
#endif /* CONFIG_CHECKPOINT */
#endif /* __KERNEL__ */
diff --git a/include/linux/checkpoint_types.h b/include/linux/checkpoint_types.h
index 912e06a..8035556 100644
--- a/include/linux/checkpoint_types.h
+++ b/include/linux/checkpoint_types.h
@@ -79,6 +79,7 @@ struct ckpt_obj_ops {
int (*ref_grab)(void *ptr);
int (*checkpoint)(struct ckpt_ctx *ctx, void *ptr);
void *(*restore)(struct ckpt_ctx *ctx);
+ struct module *owner;
};
diff --git a/kernel/checkpoint/checkpoint.c b/kernel/checkpoint/checkpoint.c
index f451f8f..1a08bfb 100644
--- a/kernel/checkpoint/checkpoint.c
+++ b/kernel/checkpoint/checkpoint.c
@@ -473,6 +473,7 @@ static int init_checkpoint_ctx(struct ckpt_ctx *ctx, pid_t pid)
{
struct task_struct *task;
struct nsproxy *nsproxy;
+ int ret;
/*
* No need for explicit cleanup here, because if an error
@@ -514,6 +515,12 @@ static int init_checkpoint_ctx(struct ckpt_ctx *ctx, pid_t pid)
return -EINVAL; /* cleanup by ckpt_ctx_free() */
}
+ /* pin down modules - cleanup by ckpt_ctx_free() */
+ ret = ckpt_obj_module_get();
+ if (ret < 0)
+ return ret;
+ ckpt_ctx_set_kflag(ctx, CKPT_CTX_PINNED);
+
return 0;
}
diff --git a/kernel/checkpoint/objhash.c b/kernel/checkpoint/objhash.c
index 1ee06d0..db795e3 100644
--- a/kernel/checkpoint/objhash.c
+++ b/kernel/checkpoint/objhash.c
@@ -45,17 +45,80 @@ static const struct ckpt_obj_ops *ckpt_obj_ops[CKPT_OBJ_MAX] = {
[CKPT_OBJ_IGNORE] = &ckpt_obj_ignored_ops,
};
+static int ckpt_obj_pinned_count;
+static DEFINE_SPINLOCK(ckpt_obj_pinned_lock);
+
int register_checkpoint_obj(const struct ckpt_obj_ops *ops)
{
+ int ret = -EINVAL;
+ int i;
+
if (ops->obj_type < 0 || ops->obj_type >= CKPT_OBJ_MAX)
return -EINVAL;
- if (ckpt_obj_ops[ops->obj_type] != NULL)
- return -EINVAL;
- ckpt_obj_ops[ops->obj_type] = ops;
- return 0;
+ spin_lock(&ckpt_obj_pinned_lock);
+ if (ckpt_obj_ops[ops->obj_type] == NULL) {
+ if (ops->owner) {
+ for (i = 0; i < ckpt_obj_pinned_count)
+ __module_get(owner->module);
+ }
+ ckpt_obj_ops[ops->obj_type] = ops;
+ ret = 0;
+ }
+ spin_unlock(&ckpt_obj_pinned_lock);
+ return ret;
}
EXPORT_SYMBOL(register_checkpoint_obj);
+void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops)
+{
+ if (ops->obj_type < 0 || ops->obj_type >= CKPT_OBJ_MAX)
+ return;
+ spin_lock(&ckpt_obj_pinned_lock);
+ if (ckpt_obj_ops[ops->obj_type] == ops)
+ ckpt_obj_ops[ops->obj_type] = NULL;
+ spin_unlock(&ckpt_obj_pinned_lock);
+ return ret;
+}
+EXPORT_SYMBOL(unregister_checkpoint_obj);
+
+static void _ckpt_obj_module_put(int last)
+{
+ int i;
+
+ for (i = 0; i < last; i++) {
+ if (!ckpt_obj_ops[i] || !ckpt_obj_ops[i]->owner)
+ continue;
+ module_put(ckpt_obj_ops[i]->owner);
+ }
+}
+void ckpt_obj_module_put(void)
+{
+ spin_lock(&ckpt_obj_pinned_lock);
+ _ckpt_obj_module_put(CKPT_OBJ_MAX);
+ ckpt_obj_pinned_count--;
+ spin_unlock(&ckpt_obj_pinned_lock);
+}
+
+int ckpt_obj_module_get(void)
+{
+ int i, ret = 0;
+
+ spin_lock(&ckpt_obj_pinned_lock);
+ for (i = 0; i < CKPT_OBJ_MAX; i++) {
+ if (!ckpt_obj_ops[i] || !ckpt_obj_ops[i]->owner)
+ continue;
+ ret = try_module_get(ckpt_obj_ops[i]->owner);
+ if (ret < 0)
+ break;
+ }
+ if (ret < 0)
+ _ckpt_obj_module_put(i);
+ else
+ ckpt_obj_pinned_count++;
+ spin_unlock(&ckpt_obj_pinned_lock);
+ return ret;
+}
+
#define CKPT_OBJ_HASH_NBITS 10
#define CKPT_OBJ_HASH_TOTAL (1UL << CKPT_OBJ_HASH_NBITS)
diff --git a/kernel/checkpoint/restart.c b/kernel/checkpoint/restart.c
index 437de4f..582e1f1 100644
--- a/kernel/checkpoint/restart.c
+++ b/kernel/checkpoint/restart.c
@@ -1084,6 +1084,12 @@ static int init_restart_ctx(struct ckpt_ctx *ctx, pid_t pid)
ctx->active_pid = -1; /* see restore_activate_next, get_active_pid */
+ /* pin down modules - cleanup by ckpt_ctx_free() */
+ ret = ckpt_obj_module_get();
+ if (ret < 0)
+ return ret;
+ ckpt_ctx_set_kflag(ctx, CKPT_CTX_PINNED);
+
return 0;
}
diff --git a/kernel/checkpoint/sys.c b/kernel/checkpoint/sys.c
index 5e84915..e1a1f96 100644
--- a/kernel/checkpoint/sys.c
+++ b/kernel/checkpoint/sys.c
@@ -217,6 +217,10 @@ static void ckpt_ctx_free(struct ckpt_ctx *ctx)
kfree(ctx->pids_arr);
+ /* un-pin modules */
+ if (ctx->kflags & CKPT_CTX_PINNED)
+ ckpt_obj_module_put();
+
kfree(ctx);
}
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