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 Tue,  4 Feb 2020 21:08:54 +0300 (MSK)
Date: Tue, 4 Feb 2020 21:08:53 +0300
From: Nikita Pettik <korablev@tarantool.org>
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Subject: Re: [Tarantool-patches] [PATCH v3 1/2] b-tree: return NULL on
 matras_alloc fail
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To: Konstantin Osipov <kostja.osipov@gmail.com>, Ilya Kosarev <i.kosarev@tarantool.org>, tarantool-patches@dev.tarantool.org, v.shpilevoy@tarantool.org

On 04 Feb 20:25, Konstantin Osipov wrote:
> * Nikita Pettik <korablev@tarantool.org> [20/02/04 20:21]:
> > > > On 20 Jan 21:13, Ilya Kosarev wrote:
> > > > > In bps_tree_create_leaf we use matras_alloc in case
> > > > > bps_tree_garbage_pop didn't work out. However it also might not
> > > > > succeed. Then we need to return NULL instead of dereferencing NULL
> > > > > pointer.
> > > 
> > > I don't understand the attempt to fix it.
> > > 
> > > The reason the allocations are not checked - most likely -because
> > > BPS should refuse to even begin an operation if there is not
> > > enough memory in matras.
> > 
> > According to the code it doesn't look so. Matras allocation checked
> > on fails, except two ones in bps_tree_create_inner() and
> > bps_tree_create_leaf().
> 
> Because reserve_blocks() should reserve enough blocks or fail, and
> it is called before create_inner/create_leaf in all execution paths?

Consider following path:

memtx_tree_index_replace
|
->memtx_tree_insert (bps_tree_insert)
  |
  ->bps_tree_insert_first_elem
    |
    ->bps_tree_create_leaf
      |
      -> matras_alloc

In this case reserve_blocks() is not called. AFAIU path is likely to
be reachable. Am I missing smth?
 
> -- 
> Konstantin Osipov, Moscow, Russia