Hi Oleg,
On 06/29/2018 01:21 AM, Oleg Nesterov wrote:
> I have to admit that after a quick glance I can't understand this patch
> at all... I'll try to read it again tomorrow, but could you at least explain
> how find_node_in_range/build_probe_list can work if off_type==REF_CTR_OFFSET?
>
> On 06/28, Ravi Bangoria wrote:
>>
>> -find_node_in_range(struct inode *inode, loff_t min, loff_t max)
>> +find_node_in_range(struct inode *inode, int off_type, loff_t min, loff_t max)
>> {
>> struct rb_node *n = uprobes_tree.rb_node;
>>
>> while (n) {
>> struct uprobe *u = rb_entry(n, struct uprobe, rb_node);
>> + loff_t offset = uprobe_get_offset(u, off_type);
>>
>> if (inode < u->inode) {
>> n = n->rb_left;
>> } else if (inode > u->inode) {
>> n = n->rb_right;
>> } else {
>> - if (max < u->offset)
>> + if (max < offset)
>> n = n->rb_left;
>> - else if (min > u->offset)
>> + else if (min > offset)
>> n = n->rb_right;
>> else
>> break;
>
> To simplify, lets forget about uprobe->inode (which acts as a key too). So uprobes_tree
> is a binary tree sorted by uprobe->offset key and that is why the binary search works.
>
> But it is not sorted by uprobe->ref_ctr_offset. So for example n->rb_left can have the
> n->ref_ctr_offset key that is greater than the n's ref_ctr_offset. So how we can use the
> binary search if REF_CTR_OFFSET?
>
> I must have missed something, I assume you tested this patch and it works somehow...
>
Right, I've misinterpreted that code. Will check it.
Thanks for explaining,
Ravi
