Re: [RFC PATCH] Introduce filesystem type tracking

[Tom Spink]

2008/5/20 Matthew Wilcox <matthew@xxxxxx>:
> On Tue, May 20, 2008 at 04:18:14PM +0100, Tom Spink wrote:
>> +
>> +     mutex_lock(&type->fs_supers_lock);
>> +     if (list_empty(&type->fs_supers) && type->init) {
>> +             err = type->init();
>> +             if (err) {
>> +                     mutex_unlock(&type->fs_supers_lock);
>> +                     spin_unlock(&sb_lock);
>> +                     destroy_super(s);
>> +                     return ERR_PTR(err);
>> +             }
>> +     }
>> +
>> +     list_add(&s->s_instances, &type->fs_supers);
>> +     mutex_unlock(&type->fs_supers_lock);
>> +
>>       s->s_type = type;
>>       strlcpy(s->s_id, type->name, sizeof(s->s_id));
>>       list_add_tail(&s->s_list, &super_blocks);
>> -     list_add(&s->s_instances, &type->fs_supers);
>> +
>>       spin_unlock(&sb_lock);
>
> You can't take a mutex while holding a spinlock -- what if you had to
> sleep to acquire the mutex?
>
> I imagine you also don't want to hold a spinlock while calling the
> ->init or ->exit -- what if the fs wants to sleep in there (eg allocate
> memory with GFP_KERNEL).
>
> --
> Intel are signing my paycheques ... these opinions are still mine
> "Bill, look, we understand that you're interested in selling us this
> operating system, but compare it to ours.  We can't possibly take such
> a retrograde step."
>

Oh no!  This is bad.  I really need to devise some script to stress
test my code - and also make myself pay attention to what I'm doing.
Sorry for the noise, guys.

-- 
Tom Spink
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