I don't feel comfortable with posting a version that we know
can crash a kernel, and even less so if we say that's it's broken...
So I prefer it inside.
Oren
Serge E. Hallyn wrote:
> 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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