linux-kernel - Re: [PATCH] maple_tree: Fix sparse reported issues

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Date:   Tue, 12 Jul 2022 15:44:09 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] maple_tree: Fix sparse reported issues

* Matthew Wilcox <willy@...radead.org> [220712 10:54]:
> On Tue, Jul 12, 2022 at 02:24:55PM +0000, Liam Howlett wrote:
> > When building with C=1, the maple tree had some rcu type mismatch &
> > locking mismatches in the destroy functions.  There were cosmetic only
> > since this happens after the nodes are removed from the tree.
> 
> ... in the current use-case.  It's a legitimate use of the API to do:
> 
> 	ma_init();
> 	ma_store();
> 	ma_destroy();
> 	ma_store();
> 
> Can you add a new test that does that?

I can add this, but a few notes on it.

The function names are mt_init(), mtree_store(), and mtree_destroy().
There is an internal/advanced __mt_destroy().  Both destroy functions
clear the flags - which I think is desirable.

> 
> > @@ -5524,13 +5526,17 @@ static void mt_destroy_walk(struct maple_enode *enode, unsigned char ma_flags,
> >  
> >  		type = mte_node_type(mas.node);
> >  		slots = ma_slots(mte_to_node(mas.node), type);
> > -		if ((offset < mt_slots[type]) && mte_node_type(slots[offset]) &&
> > -		    mte_to_node(slots[offset])) {
> > -			struct maple_enode *parent = mas.node;
> > +		if (offset >= mt_slots[type])
> > +			goto next;
> >  
> > -			mas.node = mas_slot_locked(&mas, slots, offset);
> > +		tmp = mas_slot_locked(&mas, slots, offset);
> > +		if (mte_node_type(tmp) && mte_to_node(tmp)) {
> > +
> 
> Unnecessary blank line?

ack, I'll remove that.

> 
> > +			parent = mas.node;
> > +			mas.node = tmp;
> >  			slots = mas_destroy_descend(&mas, parent, offset);
> >  		}
> > +next:
> >  		node = mas_mn(&mas);
> >  	} while (start != mas.node);
> >  
> > -- 
> > 2.35.1
> > 
> 
> -- 
> maple-tree mailing list
> maple-tree@...ts.infradead.org
> https://lists.infradead.org/mailman/listinfo/maple-tree

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