RE: [patch] hugetlb strict commit accounting

["Chen, Kenneth W" <kenneth.w.chen@intel.com>]

Chen, Kenneth W wrote on Thursday, March 09, 2006 4:02 AM
> David Gibson wrote on Thursday, March 09, 2006 3:27 AM
> > Again, there are no changes to the fault handler.  Including the
> > promised changes which would mean my instantiation serialization path
> > isn't necessary ;-).
> 
> This is the major portion that I omitted in the first patch and is the
> real kicker that fulfills the promise of guaranteed available hugetlb
> page for shared mapping.

Take a look at the following snippets of earlier patch:  in
hugetlb_reserve_pages(), region_chg() calculates an estimate how many
pages is needed, then calls to hugetlb_acct_memory() to make sure there
are enough pages available, then another call to region_add to confirm
the reservation.  It looks OK to me.


+int hugetlb_acct_memory(long delta)
+{
+	atomic_add(delta, &resv_huge_pages);
+	if (delta > 0 && atomic_read(&resv_huge_pages) >
+			VMACCTPG(hugetlb_total_pages())) {
+		atomic_add(-delta, &resv_huge_pages);
+		return -ENOMEM;
+	}
+	return 0;
+}
+
+static int hugetlb_reserve_pages(struct inode *inode, int from, int to)
+{
+	int ret, chg;
+
+	chg = region_chg(&inode->i_mapping->private_list, from, to);
+	if (chg < 0)
+		return chg;
+	ret = hugetlb_acct_memory(chg);
+	if (ret < 0)
+		return ret;
+	region_add(&inode->i_mapping->private_list, from, to);
+	return 0;
 }