On 2018/7/13 11:28, Yunlong Song wrote:
> round 1: section bitmap : 1 1 1 1 1, all valid, prefree_map: 0 0 0 0 0
> then rm data block NO.2, block NO.2 becomes invalid, prefree_map: 0 0 1 0 0
> write_checkpoint: section bitmap: 1 1 0 1 1, prefree_map: 0 0 0 0 0,
> prefree of NO.2 is cleared, and no discard issued
>
> round2: rm data block NO.0, NO.1, NO.3, NO.4
> all invalid, but prefree bit of NO.2 is set and cleared in round1, then
> prefree_map: 1 1 0 1 1
> write_checkpoint: section bitmap: 0 0 0 0 0, prefree_map: 0 0 0 1 1, no
> valid blocks of this section, so discard issued
> but this time prefree bit of NO.3 and NO.4 is skipped...
due to start = start_segno + sbi->segs_per_sec;
>
> round3:
> write_checkpoint: section bitmap: 0 0 0 0 0, prefree_map: 0 0 0 1 1 - >
> 0 0 0 0 0, no valid blocks of this section, so discard issued
> this time prefree bit of NO.3 and NO.4 is cleared, but the discard of
> this section is sent again...
Could you add this into commit log?
Thanks,
>
> On 2018/7/13 11:13, Chao Yu wrote:
>> On 2018/7/12 23:09, Yunlong Song wrote:
>>> For the case when sbi->segs_per_sec > 1, take section:segment = 5 for
>>> example, if the section prefree_map is ...previous section | current
>>> section (1 1 0 1 1) | next section..., then the start = x, end = x + 1,
>>> after start = start_segno + sbi->segs_per_sec, start = x + 5, then it
>>> will skip x + 3 and x + 4, but their bitmap is still set, which will
>>> cause duplicated f2fs_issue_discard of this same section in the next
>>> write_checkpoint, so fix it.
>> I didn't get it, if # 2 segment is not prefree state, so it still has valid
>> blocks there, so we won't issue discard due to below condition, right?
>>
>> if (!IS_CURSEC(sbi, secno) &&
>> !get_valid_blocks(sbi, start, true))
>>
>> Thanks,
>>
>>> Signed-off-by: Yunlong Song <yunlong.s...@huawei.com>
>>> ---
>>> fs/f2fs/segment.c | 19 +++++++++++++++++--
>>> 1 file changed, 17 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>> index 47b6595..fd38b61 100644
>>> --- a/fs/f2fs/segment.c
>>> +++ b/fs/f2fs/segment.c
>>> @@ -1684,8 +1684,23 @@ void f2fs_clear_prefree_segments(struct f2fs_sb_info
>>> *sbi,
>>> start = start_segno + sbi->segs_per_sec;
>>> if (start < end)
>>> goto next;
>>> - else
>>> - end = start - 1;
>>> + else {
>>> + start_segno = start;
>>> +
>>> + while (1) {
>>> + start = find_next_bit(prefree_map, start_segno,
>>> + end +
>>> 1);
>>> + if (start >= start_segno)
>>> + break;
>>> + end = find_next_zero_bit(prefree_map,
>>> start_segno,
>>> +
>>> start + 1);
>>> + for (i = start; i < end; i++)
>>> + clear_bit(i, prefree_map);
>>> + dirty_i->nr_dirty[PRE] -= end - start;
>>> + }
>>> +
>>> + end = start_segno - 1;
>>> + }
>>> }
>>> mutex_unlock(&dirty_i->seglist_lock);
>>>
>>>
>>
>> .
>>
>
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