Serge E. Hallyn wrote:
> Quoting Oren Laadan ([email protected]):
>> The task address space (task->mm) may be shared between processes if
>> CLONE_VM is used, and particularly among threads. Accordingly, treat
>> 'task->mm' as a shared object: during checkpoint check against the
>> objhash and only dump the contents if seen for the first time. During
>> restart, likewise, only restore if it's a new instance, otherwise use
>> the one already registered in the objhash.
>>
>> Signed-off-by: Oren Laadan <[email protected]>
>
> Cool.
>
> Acked-by: Serge Hallyn <[email protected]>
>
> Although:
>
>> + /* if the mm's objref is in the objhash, use that instance */
>> + mm = cr_obj_get_by_ref(ctx, hh->objref, CR_OBJ_MM);
>> + if (IS_ERR(mm)) {
>> + ret = PTR_ERR(mm);
>> + goto out;
>> + }
>>
>> + if (mm) {
>> + if (mm != current->mm) {
>
> In what twisted world could mm == current->mm at restart?
Tasks are re-created in user space, and so are threads. So threads will
already have their 'mm' set correctly.
Oren.
>
>> + ret = exec_mmap(mm);
>> + if (ret < 0)
>> + goto out;
>> + atomic_inc(&mm->mm_users);
>> + }
>> + ret = 0;
>> + goto out;
>> + }
>> +
>> + /* otherwise, add our mm to the objhash for future generations */
>> mm = current->mm;
>> + ret = cr_obj_add_ref(ctx, mm, hh->objref, CR_OBJ_MM, 0);
>> + if (ret < 0)
>> + goto out;
>>
>> /* point of no return -- destruct current mm */
>> down_write(&mm->mmap_sem);
>> diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
>> index 043535c..1bfe284 100644
>> --- a/include/linux/checkpoint.h
>> +++ b/include/linux/checkpoint.h
>> @@ -77,6 +77,7 @@ extern void cr_ctx_put(struct cr_ctx *ctx);
>> enum {
>> CR_OBJ_FILE = 1,
>> CR_OBJ_INODE,
>> + CR_OBJ_MM,
>> CR_OBJ_MAX
>> };
>>
>> --
>> 1.5.4.3
>
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