[Ocfs2-devel] [PATCH 1/3] ocfs2: Add ocfs2_trim_fs for SSD trim support.

[Tristan Ye <tristan.ye@oracle.com>]

Tao Ma wrote:
> On 03/08/2011 12:55 PM, Tristan Ye wrote:
>> Hi Tao,
>>
>>    Most of codes looks pretty neat to me, few comments inlined below:
>>
>> Tao Ma wrote:
>>> From: Tao Ma <boyu.mt@taobao.com>
>>>
>>> Add ocfs2_trim_fs to support trimming freed clusters in the
>>> volume. A range will be given and all the freed clusters greater
>>> than minlen will be discarded to the block layer.
>>>
>>> Signed-off-by: Tao Ma <boyu.mt@taobao.com>
>>> ---
>>>  fs/ocfs2/alloc.c |  154
>>> ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>>  fs/ocfs2/alloc.h |    1 +
>>>  2 files changed, 155 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
>>> index b27a0d8..6e1b3b5 100644
>>> --- a/fs/ocfs2/alloc.c
>>> +++ b/fs/ocfs2/alloc.c
> <snip>
>>> +static int ocfs2_trim_group(struct super_block *sb,
>>> +                struct ocfs2_group_desc *gd,
>>> +                int start, int max, int minbits)
>>> +{
>>> +    int ret = 0, count = 0, next;
>>> +    void *bitmap = gd->bg_bitmap;
>>> +
>>> +    while (start < max) {
>>> +        start = ocfs2_find_next_zero_bit(bitmap, max, start);
>>> +        if (start >= max)
>>> +            break;
>>    /* What if the 'start' stands within a hole */
>>
>>    if (ocfs2_test_bit(...)) {
>>       start = ocfs2_find_next_zero_bit(...);
>>       if ((start == -1) || (start >= max))
>>          break;
>>    }
> I just noticed that I forget to response to this. what do you define a
> hole? It is within the global bitmap, so it is either freed or
> allocated. I don't get your meaning of 'hole'. ocfs2_find_next_zero_bit
> will do as we expected.

	Here the hole means the area/range where contiguous '0' resides in the 
bitmap;-)


> 
> Regards,
> Tao