[PATCH] maple_tree: should get pivots boundary by type

[PATCH] maple_tree: should get pivots boundary by type

[Wei Yang]

We should get pivots boundary by type.

Fixes: 54a611b60590 (Maple Tree: add new data structure)
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
CC: Liam R. Howlett <Liam.Howlett@Oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>

---
* 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

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

[Wei Yang]

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 <richard.weiyang@gmail.com>
>CC: Liam R. Howlett <Liam.Howlett@Oracle.com>
>Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
>
>---
>* 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

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

[Andrew Morton]

On Sat, 12 Nov 2022 23:43:08 +0000 Wei Yang <richard.weiyang@gmail.com> 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
> 

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

[Liam R. Howlett]

* Andrew Morton <akpm@linux-foundation.org> [230123 16:43]:
> On Sat, 12 Nov 2022 23:43:08 +0000 Wei Yang <richard.weiyang@gmail.com> 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
> >