[PATCH] maple_tree: fix alloc node fail issue

[Jiazi Li]

On Mon, Jun 24, 2024 at 11:38:34AM -0400, Liam R. Howlett wrote:
> 
> * Jiazi Li <jqqlijiazi at gmail.com> [240624 08:01]:
> > In the following code, the second call to the mas_node_count will
> > return -ENOMEM:
> > 
> > 	mas_node_count(&maple_tree, 31);
> > 	mas_node_count(&maple_tree, 62);
> 
> This implies mas_node_count() takes a maple tree, but it takes a maple
> state.
> 
> > 
> > This is because get a node with node_count is MAPLE_ALLOC_SLOTS in
> > while loop of mas_alloc_nodes. And this will result in max_req
> > is zero in next loop.
> 
> This description could use some work on clarity.
> 
> Please provide a testcase that reproduces the issue that will go into
> tools/testing/radix-tree/maple.c  It looks like it should go around line
> 460.
> 
> 
Ok, thanks for your suggestion.
> > Signed-off-by: Jiazi Li <jiazi.li at transsion.com>
> 
> Your Signed-off-by does not match the from address.
> 
Sorry, I will use from address to signed-off in the future.
> Please add a Fixes tag.
> 
Ok.
> > ---
> >  lib/maple_tree.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> > index aa3a5df15b8e..82c236972115 100644
> > --- a/lib/maple_tree.c
> > +++ b/lib/maple_tree.c
> > @@ -1272,7 +1272,9 @@ static inline void mas_alloc_nodes(struct ma_state *mas, gfp_t gfp)
> >  
> >  		node->node_count += count;
> >  		allocated += count;
> > -		node = node->slot[0];
> > +		do {
> > +			node = node->slot[0];
> > +		} while (unlikely(node->node_count == MAPLE_ALLOC_SLOTS));
> 
> Please change this to an 'if' statement as it would be more clear what's
> going on.
> 
I think change this to an 'if', the new node we get may still be full.
For example, the following code:
	mas_alloc_node(&mas, 61);
	mas_alloc_node(&mas, 92);//will failed
> >  		requested -= count;
> >  	}
> >  	mas->alloc->total = allocated;
> > -- 
> > 2.17.1
> >