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SubjectRe: [PATCH v2 08/10] maple_tree: Rework mas_wr_slot_store() to be cleaner and more efficient.
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在 2023/5/18 06:48, Liam R. Howlett 写道:
> * Peng Zhang <zhangpeng.00@bytedance.com> [230517 04:59]:
>> The code of mas_wr_slot_store() is messy, make it clearer and concise,
>> and add comments. In addition, get whether the two gaps are empty to
>> avoid calling mas_update_gap() all the time.
>>
>> Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
>> ---
>> lib/maple_tree.c | 59 ++++++++++++++++++++----------------------------
>> 1 file changed, 24 insertions(+), 35 deletions(-)
>>
>> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
>> index bbe4c6f2858c..25a8b7d5d598 100644
>> --- a/lib/maple_tree.c
>> +++ b/lib/maple_tree.c
>> @@ -4200,49 +4200,38 @@ static inline bool mas_wr_node_store(struct ma_wr_state *wr_mas)
>> static inline bool mas_wr_slot_store(struct ma_wr_state *wr_mas)
>> {
>> struct ma_state *mas = wr_mas->mas;
>> - unsigned long lmax; /* Logical max. */
>> unsigned char offset = mas->offset;
>> + unsigned char offset_end = wr_mas->offset_end;
>> + unsigned long lmax = wr_mas->end_piv; /* Logical max. */
>> + bool gap = false;
>>
>> - if ((wr_mas->r_max > mas->last) && ((wr_mas->r_min != mas->index) ||
>> - (offset != wr_mas->node_end)))
>> + if (offset_end - offset != 1)
>> return false;
>>
>> - if (offset == wr_mas->node_end - 1)
>> - lmax = mas->max;
>> - else
>> - lmax = wr_mas->pivots[offset + 1];
>> -
>> - /* going to overwrite too many slots. */
>> - if (lmax < mas->last)
>> - return false;
>> -
>> - if (wr_mas->r_min == mas->index) {
>> - /* overwriting two or more ranges with one. */
>> - if (lmax == mas->last)
>> - return false;
>> -
>> - /* Overwriting all of offset and a portion of offset + 1. */
>> + if (mas->index == wr_mas->r_min && mas->last < lmax) {
>> + /* Overwriting the range and over a part of the next range. */
>> + gap |= !mt_slot_locked(mas->tree, wr_mas->slots, offset);
>> + gap |= !mt_slot_locked(mas->tree, wr_mas->slots, offset + 1);
>> rcu_assign_pointer(wr_mas->slots[offset], wr_mas->entry);
>> wr_mas->pivots[offset] = mas->last;
>> - goto done;
>> - }
>> -
>> - /* Doesn't end on the next range end. */
>> - if (lmax != mas->last)
>> + } else if (mas->index > wr_mas->r_min && mas->last == lmax) {
>> + /* Overwriting a part of the range and over the next range */
>> + gap |= !mt_slot_locked(mas->tree, wr_mas->slots, offset);
>> + gap |= !mt_slot_locked(mas->tree, wr_mas->slots, offset + 1);
>> + rcu_assign_pointer(wr_mas->slots[offset + 1], wr_mas->entry);
>> + wr_mas->pivots[offset] = mas->index - 1;
>> + mas->offset++; /* Keep mas accurate. */
>> + } else {
>> return false;
>
> Again here, I think you have already verified this will be a slot store
> by offset_end - offset == 1 and new_end == wr_mas->node_end.
>
> The checking of the slots for the gap could be moved outside the
> statements. WDYT?
Yes, I'll address this in v3. Thanks.
>
>> + }
>>
>> - /* Overwriting a portion of offset and all of offset + 1 */
>> - if ((offset + 1 < mt_pivots[wr_mas->type]) &&
>> - (wr_mas->entry || wr_mas->pivots[offset + 1]))
>> - wr_mas->pivots[offset + 1] = mas->last;
>> -
>> - rcu_assign_pointer(wr_mas->slots[offset + 1], wr_mas->entry);
>> - wr_mas->pivots[offset] = mas->index - 1;
>> - mas->offset++; /* Keep mas accurate. */
>> -
>> -done:
>> trace_ma_write(__func__, mas, 0, wr_mas->entry);
>> - mas_update_gap(mas);
>> + /*
>> + * Only update gap when the new entry is empty or there is an empty
>> + * entry in the original two ranges.
>> + */
>> + if (!wr_mas->entry || gap)
>> + mas_update_gap(mas);
>> return true;
>> }
>>
>> @@ -4396,7 +4385,7 @@ static inline void mas_wr_modify(struct ma_wr_state *wr_mas)
>> if (new_end == wr_mas->node_end + 1 && mas_wr_append(wr_mas))
>> return;
>>
>> - if ((wr_mas->offset_end - mas->offset <= 1) && mas_wr_slot_store(wr_mas))
>> + if (new_end == wr_mas->node_end && mas_wr_slot_store(wr_mas))
>> return;
>> else if (mas_wr_node_store(wr_mas))
>> return;
>> --
>> 2.20.1
>>

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