Re: [PATCH] reiserfs: use __GFP_NOFAIL instead of yield and retry loop for allocation

[Hans Reiser <reiser@namesys.com>]

Do you guys think you could write some nice long comments on these flags
regarding what they mean and the policies for using them?

I gotta tell you, lots of people end up just guessing as best as they can.

Hans

Andrew Morton wrote:

>Pekka J Enberg <penberg@cs.Helsinki.FI> wrote:
>  
>
>>Hi,
>>
>>Pekka J Enberg <penberg@cs.Helsinki.FI> wrote:
>>    
>>
>>>> -      retry:
>>>> -	jl = kzalloc(sizeof(struct reiserfs_journal_list), GFP_NOFS);
>>>> -	if (!jl) {
>>>> -		yield();
>>>> -		goto retry;
>>>> -	}
>>>> +	jl = kzalloc(sizeof(struct reiserfs_journal_list),
>>>> +		     GFP_NOFS | __GFP_NOFAIL);
>>>>        
>>>>
>>On Thu, 12 Jan 2006, Andrew Morton wrote:
>>    
>>
>>>yup, that's what __GFP_NOFAIL is for: to consolidate and identify all those
>>>places which want to lock up when we're short of memory...  They all need
>>>fixing, really.
>>>      
>>>
>>Out of curiosity, are there any potential problems with combining GFP_NOFS 
>>and __GFP_NOFAIL? Can we really guarantee to give out memory if we're not 
>>allowed to page out?
>>
>>    
>>
>
>GFP_NOFS increases the risk (relative to GFP_KERNEL) because page reclaim
>can do less things than GFP_KERNEL to free memory.
>
>GFP_NOFS allocations can still perform swapspace writes, however.  GFP_NOIO
>cannot even do that.
>
>
>  
>