Re: [RFC] [PATCHv3 2/9] reiser4: block_alloc: add a "forward" parameter to reiser4_blocknr_hint to allocate blocks only in forward direction.

[Edward Shishkin <edward.shishkin@gmail.com>]

On 10/23/2014 09:24 AM, Ivan Shapovalov wrote:
> On Tuesday 21 October 2014 at 17:50:23, Edward Shishkin wrote:	
>> On 08/17/2014 11:52 PM, Ivan Shapovalov wrote:
>>> Signed-off-by: Ivan Shapovalov<intelfx100@gmail.com>
>>> ---
>>>    fs/reiser4/block_alloc.h         | 5 +++--
>>>    fs/reiser4/plugin/space/bitmap.c | 3 ++-
>>>    2 files changed, 5 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/fs/reiser4/block_alloc.h b/fs/reiser4/block_alloc.h
>>> index bfc6be9..08b3941 100644
>>> --- a/fs/reiser4/block_alloc.h
>>> +++ b/fs/reiser4/block_alloc.h
>>> @@ -51,9 +51,10 @@ struct reiser4_blocknr_hint {
>>>    	/* block allocator assumes that blocks, which will be mapped to disk,
>>>    	   are in this specified block_stage */
>>>    	block_stage_t block_stage;
>>> -	/* If direction = 1 allocate blocks in backward direction from the end
>>> -	 * of disk to the beginning of disk.  */
>>> +	/* Allocate blocks only in backward direction starting from blk. */
>>>    	unsigned int backward:1;
>>> +	/* Allocate blocks only in forward direction starting from blk. */
>>> +	unsigned int forward:1;
>>
>> I suggest to call this bitfield "monotonic_forward"
> Isn't it an opposite of "backward"? Should we rename both?


No, it isn't. And this is the reason of the rename.
monotonic_forward is to skip the second pass in alloc_blocks_forward()


>
> BTW, in plugin/space/bitmap.c:1141 (around that line)
> in function alloc_blocks_forward()
> shouldn't the second scan be done with bitmap_alloc_backward(), as per the
> comment?


I think that those comment means a jump in backward direction
(to the start) and one more pass with bitmap_alloc_forward().
Such a "compound, non-monotonic" forward...

Edward.