2022-11-13 00:03:27

by Wei Yang

Subject: [PATCH] maple_tree: should get pivots boundary by type

We should get pivots boundary by type.

Fixes: 54a611b60590 (Maple Tree: add new data structure)
Signed-off-by: Wei Yang <[email protected]>
CC: Liam R. Howlett <[email protected]>
Reviewed-by: Liam R. Howlett <[email protected]>

---
* kernel build looks good
---
lib/maple_tree.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 73e2e6434e2f..2123d1930a9b 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -669,12 +669,13 @@ static inline unsigned long mte_pivot(const struct maple_enode *mn,
unsigned char piv)
{
struct maple_node *node = mte_to_node(mn);
+ enum maple_type type = mte_node_type(mn);

- if (piv >= mt_pivots[piv]) {
+ if (piv >= mt_pivots[type]) {
WARN_ON(1);
return 0;
}
- switch (mte_node_type(mn)) {
+ switch (type) {
case maple_arange_64:
return node->ma64.pivot[piv];
case maple_range_64:
--
2.33.1

2022-12-25 07:02:19

by Wei Yang

Subject: Re: [PATCH] maple_tree: should get pivots boundary by type

May I ask who would pick this?

On Sat, Nov 12, 2022 at 11:43:08PM +0000, Wei Yang wrote:
>We should get pivots boundary by type.
>
>Fixes: 54a611b60590 (Maple Tree: add new data structure)
>Signed-off-by: Wei Yang <[email protected]>
>CC: Liam R. Howlett <[email protected]>
>Reviewed-by: Liam R. Howlett <[email protected]>
>
>---
>* kernel build looks good
>---
> lib/maple_tree.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
>diff --git a/lib/maple_tree.c b/lib/maple_tree.c
>index 73e2e6434e2f..2123d1930a9b 100644
>--- a/lib/maple_tree.c
>+++ b/lib/maple_tree.c
>@@ -669,12 +669,13 @@ static inline unsigned long mte_pivot(const struct maple_enode *mn,
> unsigned char piv)
> {
> struct maple_node *node = mte_to_node(mn);
>+ enum maple_type type = mte_node_type(mn);
>
>- if (piv >= mt_pivots[piv]) {
>+ if (piv >= mt_pivots[type]) {
> WARN_ON(1);
> return 0;
> }
>- switch (mte_node_type(mn)) {
>+ switch (type) {
> case maple_arange_64:
> return node->ma64.pivot[piv];
> case maple_range_64:
>--
>2.33.1

--
Wei Yang
Help you, Help me

2023-01-23 21:43:52

by Andrew Morton

Subject: Re: [PATCH] maple_tree: should get pivots boundary by type

On Sat, 12 Nov 2022 23:43:08 +0000 Wei Yang <[email protected]> wrote:

> We should get pivots boundary by type.
>

When fixing a bug, please always fully describe the runtime effects of
that bug.

I see from earlier review that the bug could result in overindexing
mt_pivots[], but Liam says this code isn't presently used, but
mas_alloc() calls mte_pivot(), so I'm all confused.


> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -669,12 +669,13 @@ static inline unsigned long mte_pivot(const struct maple_enode *mn,
> unsigned char piv)
> {
> struct maple_node *node = mte_to_node(mn);
> + enum maple_type type = mte_node_type(mn);
>
> - if (piv >= mt_pivots[piv]) {
> + if (piv >= mt_pivots[type]) {
> WARN_ON(1);
> return 0;
> }
> - switch (mte_node_type(mn)) {
> + switch (type) {
> case maple_arange_64:
> return node->ma64.pivot[piv];
> case maple_range_64:
> --
> 2.33.1
>

2023-01-23 22:35:38

by Liam R. Howlett

Subject: Re: [PATCH] maple_tree: should get pivots boundary by type

* Andrew Morton <[email protected]> [230123 16:43]:
> On Sat, 12 Nov 2022 23:43:08 +0000 Wei Yang <[email protected]> wrote:
>
> > We should get pivots boundary by type.
> >
>
> When fixing a bug, please always fully describe the runtime effects of
> that bug.
>
> I see from earlier review that the bug could result in overindexing
> mt_pivots[], but Liam says this code isn't presently used, but
> mas_alloc() calls mte_pivot(), so I'm all confused.

Correct. The function mas_alloc() is... very much not well named. It
is called from mtree_alloc_range() which will put a temporary value into
the tree so that you may store over that value later without allocating
memory later. It's about allocating a range, not memory. Perhaps
mas_reserve() would have been better, in retrospect.

Anyways, it's not used by the mm code right now, but it's certainly a
bug.

>
>
> > --- a/lib/maple_tree.c
> > +++ b/lib/maple_tree.c
> > @@ -669,12 +669,13 @@ static inline unsigned long mte_pivot(const struct maple_enode *mn,
> > unsigned char piv)
> > {
> > struct maple_node *node = mte_to_node(mn);
> > + enum maple_type type = mte_node_type(mn);
> >
> > - if (piv >= mt_pivots[piv]) {
> > + if (piv >= mt_pivots[type]) {
> > WARN_ON(1);
> > return 0;
> > }
> > - switch (mte_node_type(mn)) {
> > + switch (type) {
> > case maple_arange_64:
> > return node->ma64.pivot[piv];
> > case maple_range_64:
> > --
> > 2.33.1
> >