* Peng Zhang <perlyzhang@xxxxxxxxx> [230427 07:20]:
>
>
> 在 2023/4/25 22:09, 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@xxxxxxxxxx>
> > ---
> > 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 20f0a10dc5608..31cbfd7b44728 100644
> > --- a/lib/maple_tree.c
> > +++ b/lib/maple_tree.c
> > @@ -5099,24 +5099,25 @@ void *mas_walk(struct ma_state *mas)
> > {
> > void *entry;
> > + if (mas_is_none(mas) || mas_is_paused(mas))
> > + mas->node = MAS_START;
> > 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 mas_root(mas);
> Why we call mas_root() to get the single entry stored in root again?
> I think it's not safe. In RCU mode, if someone modify the tree to a normal
> tree(not a single entry tree), mas_root() will return a address.
> So, this may cause a race bug. We can return entry directly.
Good catch. I will address this in v2.
> > }
> > - 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;
