A vmap_area can travel between different places. For example
attached/detached to/from different rb-trees. In order to
prevent fancy bugs, initialize a VA's list node after it is
removed from the list, so it pairs with VA's rb_node which
is also initialized.
There is no functional change as a result of this patch.
Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
---
mm/vmalloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 745e89eb6ca1..82771e555273 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -978,7 +978,7 @@ __unlink_va(struct vmap_area *va, struct rb_root *root, bool augment)
else
rb_erase(&va->rb_node, root);
- list_del(&va->list);
+ list_del_init(&va->list);
RB_CLEAR_NODE(&va->rb_node);
}
--
2.30.2
On 06/07/22 at 11:34am, Uladzislau Rezki (Sony) wrote:
> A vmap_area can travel between different places. For example
> attached/detached to/from different rb-trees. In order to
> prevent fancy bugs, initialize a VA's list node after it is
> removed from the list, so it pairs with VA's rb_node which
> is also initialized.
>
> There is no functional change as a result of this patch.
>
> Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
> ---
> mm/vmalloc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 745e89eb6ca1..82771e555273 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -978,7 +978,7 @@ __unlink_va(struct vmap_area *va, struct rb_root *root, bool augment)
> else
> rb_erase(&va->rb_node, root);
>
> - list_del(&va->list);
> + list_del_init(&va->list);
Don't object this change, while list_del poison members, which is also
not bad?
static inline void list_del(struct list_head *entry)
{
__list_del_entry(entry);
entry->next = LIST_POISON1;
entry->prev = LIST_POISON2;
}
> RB_CLEAR_NODE(&va->rb_node);
> }
>
> --
> 2.30.2
>
>
>
> On 06/07/22 at 11:34am, Uladzislau Rezki (Sony) wrote:
> > A vmap_area can travel between different places. For example
> > attached/detached to/from different rb-trees. In order to
> > prevent fancy bugs, initialize a VA's list node after it is
> > removed from the list, so it pairs with VA's rb_node which
> > is also initialized.
> >
> > There is no functional change as a result of this patch.
> >
> > Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
> > ---
> > mm/vmalloc.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index 745e89eb6ca1..82771e555273 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -978,7 +978,7 @@ __unlink_va(struct vmap_area *va, struct rb_root *root, bool augment)
> > else
> > rb_erase(&va->rb_node, root);
> >
> > - list_del(&va->list);
> > + list_del_init(&va->list);
>
> Don't object this change, while list_del poison members, which is also
> not bad?
>
It is not bad for sure. The main aim was to be align with what the
RB_CLEAR_NODE() does, i.e. initialize VA when it is detached
and be safe with list manipulation when it is detached. For example
whether it is empty or not: list_empty(), etc.
--
Uladzislau Rezki
On 06/09/22 at 02:36pm, Uladzislau Rezki wrote:
> >
> > On 06/07/22 at 11:34am, Uladzislau Rezki (Sony) wrote:
> > > A vmap_area can travel between different places. For example
> > > attached/detached to/from different rb-trees. In order to
> > > prevent fancy bugs, initialize a VA's list node after it is
> > > removed from the list, so it pairs with VA's rb_node which
> > > is also initialized.
> > >
> > > There is no functional change as a result of this patch.
> > >
> > > Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
> > > ---
> > > mm/vmalloc.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > > index 745e89eb6ca1..82771e555273 100644
> > > --- a/mm/vmalloc.c
> > > +++ b/mm/vmalloc.c
> > > @@ -978,7 +978,7 @@ __unlink_va(struct vmap_area *va, struct rb_root *root, bool augment)
> > > else
> > > rb_erase(&va->rb_node, root);
> > >
> > > - list_del(&va->list);
> > > + list_del_init(&va->list);
> >
> > Don't object this change, while list_del poison members, which is also
> > not bad?
> >
> It is not bad for sure. The main aim was to be align with what the
> RB_CLEAR_NODE() does, i.e. initialize VA when it is detached
> and be safe with list manipulation when it is detached. For example
> whether it is empty or not: list_empty(), etc.
Agree. list_del() can't make list_empty() work, and RB_CLEAR_NODE() has
done the clearing already.
Then this change looks reasonable to me, thanks.
Reviewed-by: Baoquan He <[email protected]>
On Thu, Jun 9, 2022 at 3:30 PM Baoquan He <[email protected]> wrote:
>
> On 06/09/22 at 02:36pm, Uladzislau Rezki wrote:
> > >
> > > On 06/07/22 at 11:34am, Uladzislau Rezki (Sony) wrote:
> > > > A vmap_area can travel between different places. For example
> > > > attached/detached to/from different rb-trees. In order to
> > > > prevent fancy bugs, initialize a VA's list node after it is
> > > > removed from the list, so it pairs with VA's rb_node which
> > > > is also initialized.
> > > >
> > > > There is no functional change as a result of this patch.
> > > >
> > > > Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
> > > > ---
> > > > mm/vmalloc.c | 2 +-
> > > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > > > index 745e89eb6ca1..82771e555273 100644
> > > > --- a/mm/vmalloc.c
> > > > +++ b/mm/vmalloc.c
> > > > @@ -978,7 +978,7 @@ __unlink_va(struct vmap_area *va, struct rb_root *root, bool augment)
> > > > else
> > > > rb_erase(&va->rb_node, root);
> > > >
> > > > - list_del(&va->list);
> > > > + list_del_init(&va->list);
> > >
> > > Don't object this change, while list_del poison members, which is also
> > > not bad?
> > >
> > It is not bad for sure. The main aim was to be align with what the
> > RB_CLEAR_NODE() does, i.e. initialize VA when it is detached
> > and be safe with list manipulation when it is detached. For example
> > whether it is empty or not: list_empty(), etc.
>
> Agree. list_del() can't make list_empty() work, and RB_CLEAR_NODE() has
> done the clearing already.
>
> Then this change looks reasonable to me, thanks.
>
> Reviewed-by: Baoquan He <[email protected]>
>
Thanks!
--
Uladzislau Rezki