linux-kernel - Re: [PATCH v2 32/36] maple_tree: Clear up index and last setting in single entry tree

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Date:   Fri, 12 May 2023 11:54:27 -0400
From:   "Liam R. Howlett" <Liam.Howlett@...cle.com>
To:     Peng Zhang <zhangpeng.00@...edance.com>
Cc:     maple-tree@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 32/36] maple_tree: Clear up index and last setting in
 single entry tree

* Peng Zhang <zhangpeng.00@...edance.com> [230509 08:39]:
> 
> 
> 在 2023/5/6 01:42, Liam R. Howlett 写道:
> > When there is a single entry tree (range of 0-0 pointing to an entry),
> > then ensure the limit is either 0-0 or 1-oo, depending on where the user
> > walks.  Ensure the correct node setting as well; either MAS_ROOT or
> > MAS_NONE.
> > 
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> > ---
> >   lib/maple_tree.c | 21 +++++++++++----------
> >   1 file changed, 11 insertions(+), 10 deletions(-)
> > 
> > diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> > index f060c71965c0d..914399519cf54 100644
> > --- a/lib/maple_tree.c
> > +++ b/lib/maple_tree.c
> > @@ -5022,24 +5022,25 @@ void *mas_walk(struct ma_state *mas)
> >   {
> >   	void *entry;
> > +	if (mas_is_none(mas) || mas_is_paused(mas))
> if (mas_is_none(mas) || mas_is_paused(mas) || mas_is_ptr(mas))
> > +		mas->node = MAS_START;
> 
> Hi, Liam
> There is an issue that it cannot pass the user space test program
> with this patchset.
> I tested it based on 47cba14ce6fc4(linux-next/master).
> 
> The reason is that mas_walk() does not handle the state that mas is
> root. The root cause is that mas_start() only handles the start state,
> and returns NULL for the root state. When encountering the root state,
> we can reset to start so that it is handled in mas_start().

Thanks.  I'll have a look and adjust v3.

> 
> log:
> BUG at check_state_handling:3076 (1)
> maple_tree(0x55d6a9838ca0) flags 1, height 0 root 0x1234500
> 0: 0x1234500
> Pass: 453406336 Run:453406337
> maple: ../../../lib/test_maple_tree.c:3076: check_state_handling: Assertion
> `0' failed.
> Aborted (core dumped)
> >   retry:
> >   	entry = mas_state_walk(mas);
> > -	if (mas_is_start(mas))
> > +	if (mas_is_start(mas)) {
> >   		goto retry;
> > -
> > -	if (mas_is_ptr(mas)) {
> > +	} else if (mas_is_none(mas)) {
> > +		mas->index = 0;
> > +		mas->last = ULONG_MAX;
> > +	} else if (mas_is_ptr(mas)) {
> >   		if (!mas->index) {
> >   			mas->last = 0;
> > -		} else {
> > -			mas->index = 1;
> > -			mas->last = ULONG_MAX;
> > +			return entry;
> >   		}
> > -		return entry;
> > -	}
> > -	if (mas_is_none(mas)) {
> > -		mas->index = 0;
> > +		mas->index = 1;
> >   		mas->last = ULONG_MAX;
> > +		mas->node = MAS_NONE;
> > +		return NULL;
> >   	}
> >   	return entry;