Quoting Oren Laadan (orenl@xxxxxxxxxxxxxxx):
> 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>
Yes this looks good to me
Acked-by: Serge Hallyn <serue@xxxxxxxxxx>
Were you going to stick this into v21 too, or queue that up as
first patch after the patchbomb?
thanks,
-serge
>
> ---
> 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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