| Message ID | 20220607093449.3100-4-urezki@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Reduce a vmalloc internal lock contention preparation work | expand |
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) <urezki@gmail.com> > --- > 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) <urezki@gmail.com> > > --- > > 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.
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) <urezki@gmail.com> > > > --- > > > 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 <bhe@redhat.com>
On Thu, Jun 9, 2022 at 3:30 PM Baoquan He <bhe@redhat.com> 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) <urezki@gmail.com> > > > > --- > > > > 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 <bhe@redhat.com> > Thanks!
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); }
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) <urezki@gmail.com> --- mm/vmalloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)