[PATCH bug-fix] drbd: compute the end before rb_insert_augmented()

From: Lai Jiangshan
Date: Tue Sep 16 2014 - 22:26:31 EST

986836503e49 ("Merge branch 'drbd-8.4_ed6' into for-3.8-drivers-drbd-8.4_ed6")
changes rb_augment_insert() to new augment API. But the new API
rb_insert_augmented() requires the tree is augmennted before called.

Quote from Documentation/rbtree.txt:
On insertion, the user must update the augmented information on the path
leading to the inserted node, then call rb_link_node() as usual and
rb_augment_inserted() instead of the usual rb_insert_color() call.
If rb_augment_inserted() rebalances the rbtree, it will callback into
a user provided function to update the augmented information on the
affected subtrees.

So we add the augment-code to drbd_insert_interval() when it travels
the tree up to down before rb_insert_augmented(). See the example in
include/linux/interval_tree_generic.h or Documentation/rbtree.txt.

drbd_insert_interval() may cancel the insertion when traveling,
in this case, the just added augment-code does nothing before cancel
since the @this node is already in the subtrees in this case.

CC: Michel Lespinasse <walken@xxxxxxxxxx>
Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
drivers/block/drbd/drbd_interval.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/block/drbd/drbd_interval.c b/drivers/block/drbd/drbd_interval.c
index 89c497c..04a14e0 100644
--- a/drivers/block/drbd/drbd_interval.c
+++ b/drivers/block/drbd/drbd_interval.c
@@ -79,6 +79,7 @@ bool
drbd_insert_interval(struct rb_root *root, struct drbd_interval *this)
struct rb_node **new = &root->rb_node, *parent = NULL;
+ sector_t this_end = this->sector + (this->size >> 9);

BUG_ON(!IS_ALIGNED(this->size, 512));

@@ -87,6 +88,8 @@ drbd_insert_interval(struct rb_root *root, struct drbd_interval *this)
rb_entry(*new, struct drbd_interval, rb);

parent = *new;
+ if (here->end < this_end)
+ here->end = this_end;
if (this->sector < here->sector)
new = &(*new)->rb_left;
else if (this->sector > here->sector)
@@ -99,6 +102,7 @@ drbd_insert_interval(struct rb_root *root, struct drbd_interval *this)
return false;

+ this->end = this_end;
rb_link_node(&this->rb, parent, new);
rb_insert_augmented(&this->rb, root, &augment_callbacks);
return true;

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/