Re: [PATCH 04/13] libmultipath: Add bio handling

[John Garry <john.g.garry@oracle.com>]

On 02/03/2026 12:39, Nilay Shroff wrote:
>> static struct mpath_device *mpath_find_path(struct mpath_head 
>> *mpath_head)
>>   {
>>       enum mpath_iopolicy_e iopolicy =
>> @@ -243,6 +243,66 @@ static struct mpath_device 
>> *mpath_find_path(struct mpath_head *mpath_head)
>>       }
>>   }
>> +static bool mpath_available_path(struct mpath_head *mpath_head)
>> +{
>> +    struct mpath_device *mpath_device;
>> +
>> +    if (!test_bit(MPATH_HEAD_DISK_LIVE, &mpath_head->flags))
>> +        return false;
>> +
>> +    list_for_each_entry_srcu(mpath_device, &mpath_head->dev_list, 
>> siblings,
>> +                 srcu_read_lock_held(&mpath_head->srcu)) {
>> +        bool available = false;
>> +
>> +        if (!mpath_head->mpdt->available_path(mpath_device,
>> +                &available))
>> +            continue;
>> +        if (available)
>> +            return true;
>> +    }
>> +
>> +    return false;
>> +}
> 
> IMO, we may further simplify the callback ->available_path() to return 
> true or false instead of passing the result in a separate @available 
> argument.

I have to admit that I am not keen on this abstraction at all, as it is 
purely generated to fit the current code.

Anyway, from checking mainline nvme_available_path(), we skip checking 
the ctrl state if the ctrl failfast flag is set (which means 
mpath_head->mpdt->available_path returns false). But I suppose the 
callback could check both the ctrl flags and state (and just return a 
single boolean), like:

if (failfast flag set)
	return false;
if (ctrl live, resetting, connecting)
	return true;
return false;

Thanks,
John