+
+void hugetlb_change_protection(struct vm_area_struct *vma,
+ unsigned long address, unsigned long end, pgprot_t newprot)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ unsigned long start = address;
+ pte_t *ptep;
+ pte_t pte;
+
+ BUG_ON(address >= end);
+ flush_cache_range(vma, address, end);
+
+ spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
+ spin_lock(&mm->page_table_lock);
+ for (; address < end; address += HPAGE_SIZE) {
+ ptep = huge_pte_offset(mm, address);
+ if (!ptep)
+ continue;
+ if (huge_pmd_unshare(mm, &address, ptep))
+ continue;
+ if (!pte_none(*ptep)) {
+ pte = huge_ptep_get_and_clear(mm, address, ptep);
+ pte = pte_mkhuge(pte_modify(pte, newprot));
+ set_huge_pte_at(mm, address, ptep, pte);
+ lazy_mmu_prot_update(pte);
+ }
+ }
+ spin_unlock(&mm->page_table_lock);
+ spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
+
+ flush_tlb_range(vma, start, end);
+}
+
+struct file_region {
+ struct list_head link;
+ long from;
+ long to;
+};
+
+static long region_add(struct list_head *head, long f, long t)
+{
+ struct file_region *rg, *nrg, *trg;
+
+ /* Locate the region we are either in or before. */
+ list_for_each_entry(rg, head, link)
+ if (f <= rg->to)
+ break;
+
+ /* Round our left edge to the current segment if it encloses us. */
+ if (f > rg->from)
+ f = rg->from;
+
+ /* Check for and consume any regions we now overlap with. */
+ nrg = rg;
+ list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
+ if (&rg->link == head)
+ break;
+ if (rg->from > t)
+ break;
+
+ /* If this area reaches higher then extend our area to
+ * include it completely. If this is not the first area
+ * which we intend to reuse, free it. */
+ if (rg->to > t)
+ t = rg->to;
+ if (rg != nrg) {
+ list_del(&rg->link);
+ kfree(rg);
+ }
+ }
+ nrg->from = f;
+ nrg->to = t;
+ return 0;
+}
+
+static long region_chg(struct list_head *head, long f, long t)
+{
+ struct file_region *rg, *nrg;
+ long chg = 0;
+
+ /* Locate the region we are before or in. */
+ list_for_each_entry(rg, head, link)
+ if (f <= rg->to)
+ break;
+
+ /* If we are below the current region then a new region is required.
+ * Subtle, allocate a new region at the position but make it zero
+ * size such that we can guarentee to record the reservation. */
+ if (&rg->link == head || t < rg->from) {
+ nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
+ if (nrg == 0)
+ return -ENOMEM;
+ nrg->from = f;
+ nrg->to = f;
+ INIT_LIST_HEAD(&nrg->link);
+ list_add(&nrg->link, rg->link.prev);
+
+ return t - f;
+ }
+
+ /* Round our left edge to the current segment if it encloses us. */
+ if (f > rg->from)
+ f = rg->from;
+ chg = t - f;
+
+ /* Check for and consume any regions we now overlap with. */
+ list_for_each_entry(rg, rg->link.prev, link) {
+ if (&rg->link == head)
+ break;
+ if (rg->from > t)
+ return chg;
+
+ /* We overlap with this area, if it extends futher than
+ * us then we must extend ourselves. Account for its
+ * existing reservation. */
+ if (rg->to > t) {
+ chg += rg->to - t;
+ t = rg->to;
+ }
+ chg -= rg->to - rg->from;
+ }
+ return chg;
+}
+
+static long region_truncate(struct list_head *head, long end)
+{
+ struct file_region *rg, *trg;
+ long chg = 0;
+
+ /* Locate the region we are either in or before. */
+ list_for_each_entry(rg, head, link)
+ if (end <= rg->to)
+ break;
+ if (&rg->link == head)
+ return 0;
+
+ /* If we are in the middle of a region then adjust it. */
+ if (end > rg->from) {
+ chg = rg->to - end;
+ rg->to = end;
+ rg = list_entry(rg->link.next, typeof(*rg), link);
+ }
+
+ /* Drop any remaining regions. */
+ list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
+ if (&rg->link == head)
+ break;
+ chg += rg->to - rg->from;
+ list_del(&rg->link);
+ kfree(rg);
+ }
+ return chg;
+}
+
+static int hugetlb_acct_memory(long delta)
+{
+ int ret = -ENOMEM;
+
+ spin_lock(&hugetlb_lock);
+ if ((delta + resv_huge_pages) <= free_huge_pages) {
+ resv_huge_pages += delta;
+ ret = 0;
+ }
+ spin_unlock(&hugetlb_lock);
+ return ret;
+}
+
+int hugetlb_reserve_pages(struct inode *inode, long from, long to)
+{
+ long ret, chg;
+
+ chg = region_chg(&inode->i_mapping->private_list, from, to);
+ if (chg < 0)
+ return chg;
+ /*
+ * When cpuset is configured, it breaks the strict hugetlb page
+ * reservation as the accounting is done on a global variable. Such
+ * reservation is completely rubbish in the presence of cpuset because
+ * the reservation is not checked against page availability for the
+ * current cpuset. Application can still potentially OOM'ed by kernel
+ * with lack of free htlb page in cpuset that the task is in.
+ * Attempt to enforce strict accounting with cpuset is almost
+ * impossible (or too ugly) because cpuset is too fluid that
+ * task or memory node can be dynamically moved between cpusets.
+ *
+ * The change of semantics for shared hugetlb mapping with cpuset is
+ * undesirable. However, in order to preserve some of the semantics,
+ * we fall back to check against current free page availability as
+ * a best attempt and hopefully to minimize the impact of changing
+ * semantics that cpuset has.
+ */
+ if (chg > cpuset_mems_nr(free_huge_pages_node))
+ return -ENOMEM;
+
+ ret = hugetlb_acct_memory(chg);
+ if (ret < 0)
+ return ret;
+ region_add(&inode->i_mapping->private_list, from, to);
+ return 0;
+}
+
+void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
+{
+ long chg = region_truncate(&inode->i_mapping->private_list, offset);
+ hugetlb_acct_memory(freed - chg);
+}