Re: [PATCH v2 07/10] maple_tree: Add comments and some minor cleanups to mas_wr_append()

[Peng Zhang]

在 2023/5/18 03:33, Liam R. Howlett 写道:
> * Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx> [230517 04:59]:
> > Add comment for mas_wr_append(), move mas_update_gap() into
> > mas_wr_append(), and other cleanups to make mas_wr_modify() cleaner.
> >
> > Signed-off-by: Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx>
> > ---
> >   lib/maple_tree.c | 33 ++++++++++++++++++++-------------
> >   1 file changed, 20 insertions(+), 13 deletions(-)
> >
> > diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> > index 3b9d227f3d7d..bbe4c6f2858c 100644
> > --- a/lib/maple_tree.c
> > +++ b/lib/maple_tree.c
> > @@ -4308,6 +4308,12 @@ static inline unsigned char mas_wr_new_end(struct ma_wr_state *wr_mas)
> >   	return new_end;
> >   }
> >   
> > +/*
> > + * mas_wr_append: Attempt to append
> > + * @wr_mas: the maple write state
> > + *
> > + * Return: True if appended, false otherwise
> > + */
> >   static inline bool mas_wr_append(struct ma_wr_state *wr_mas)
> >   {
> >   	unsigned char end = wr_mas->node_end;
> > @@ -4315,7 +4321,11 @@ static inline bool mas_wr_append(struct ma_wr_state *wr_mas)
> >   	struct ma_state *mas = wr_mas->mas;
> >   	unsigned char node_pivots = mt_pivots[wr_mas->type];
> >   
> > +	if (!(mas->offset == wr_mas->node_end))
> > +		return false;
> > +
> >   	if ((mas->index != wr_mas->r_min) && (mas->last == wr_mas->r_max)) {
> > +		/* Append to end of range */
> >   		if (new_end < node_pivots)
> >   			wr_mas->pivots[new_end] = wr_mas->pivots[end];
> >   
> > @@ -4323,13 +4333,10 @@ static inline bool mas_wr_append(struct ma_wr_state *wr_mas)
> >   			ma_set_meta(wr_mas->node, maple_leaf_64, 0, new_end);
> >   
> >   		rcu_assign_pointer(wr_mas->slots[new_end], wr_mas->entry);
> > -		mas->offset = new_end;
> >   		wr_mas->pivots[end] = mas->index - 1;
> > -
> > -		return true;
> > -	}
> > -
> > -	if ((mas->index == wr_mas->r_min) && (mas->last < wr_mas->r_max)) {
> > +		mas->offset = new_end;
> > +	} else if ((mas->index == wr_mas->r_min) && (mas->last < wr_mas->r_max)) {
> > +		/* Append to start of range */
> >   		if (new_end < node_pivots)
> >   			wr_mas->pivots[new_end] = wr_mas->pivots[end];
> >   
> > @@ -4339,10 +4346,13 @@ static inline bool mas_wr_append(struct ma_wr_state *wr_mas)
> >   
> >   		wr_mas->pivots[end] = mas->last;
> >   		rcu_assign_pointer(wr_mas->slots[end], wr_mas->entry);
> > -		return true;
> > +	} else {
> > +		return false;
>
> I don't think we can get here with your changes, what do you think?  If
> so, we can move the metadata setting to the outside of the if/else.  I
> checked by adding a BUG_ON() and the test code never gets here.
>
> My thinking is, we know offset == node_end and new_end == node_end + 1..
> so we must be inserting into the last slot and only adding one entry.
Yes, I'll address this in v3. Thanks.
> >   	}
> >   
> > -	return false;
> > +	if (!wr_mas->content || !wr_mas->entry)
> > +		mas_update_gap(mas);
> > +	return  true;
> >   }
> >   
> >   /*
> > @@ -4382,12 +4392,9 @@ static inline void mas_wr_modify(struct ma_wr_state *wr_mas)
> >   	if (new_end >= mt_slots[wr_mas->type])
> >   		goto slow_path;
> >   
> > -	if (wr_mas->entry && (wr_mas->node_end < mt_slots[wr_mas->type] - 1) &&
> > -	    (mas->offset == wr_mas->node_end) && mas_wr_append(wr_mas)) {
> > -		if (!wr_mas->content || !wr_mas->entry)
> > -			mas_update_gap(mas);
> > +	/* Attempt to append */
> > +	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))
> >   		return;
> > --
> > 2.20.1