2 * Generic hugetlb support.
3 * (C) William Irwin, April 2004
6 #include <linux/list.h>
7 #include <linux/init.h>
8 #include <linux/module.h>
10 #include <linux/sysctl.h>
11 #include <linux/highmem.h>
12 #include <linux/nodemask.h>
13 #include <linux/pagemap.h>
14 #include <linux/mempolicy.h>
15 #include <linux/cpuset.h>
16 #include <linux/mutex.h>
19 #include <asm/pgtable.h>
21 #include <linux/hugetlb.h>
24 const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
25 static unsigned long nr_huge_pages, free_huge_pages, resv_huge_pages;
26 static unsigned long surplus_huge_pages;
27 unsigned long max_huge_pages;
28 static struct list_head hugepage_freelists[MAX_NUMNODES];
29 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
30 static unsigned int free_huge_pages_node[MAX_NUMNODES];
31 static unsigned int surplus_huge_pages_node[MAX_NUMNODES];
32 static gfp_t htlb_alloc_mask = GFP_HIGHUSER;
33 unsigned long hugepages_treat_as_movable;
34 int hugetlb_dynamic_pool;
37 * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
39 static DEFINE_SPINLOCK(hugetlb_lock);
41 static void clear_huge_page(struct page *page, unsigned long addr)
46 for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
48 clear_user_highpage(page + i, addr + i * PAGE_SIZE);
52 static void copy_huge_page(struct page *dst, struct page *src,
53 unsigned long addr, struct vm_area_struct *vma)
58 for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) {
60 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
64 static void enqueue_huge_page(struct page *page)
66 int nid = page_to_nid(page);
67 list_add(&page->lru, &hugepage_freelists[nid]);
69 free_huge_pages_node[nid]++;
72 static struct page *dequeue_huge_page(struct vm_area_struct *vma,
73 unsigned long address)
76 struct page *page = NULL;
77 struct mempolicy *mpol;
78 struct zonelist *zonelist = huge_zonelist(vma, address,
79 htlb_alloc_mask, &mpol);
82 for (z = zonelist->zones; *z; z++) {
83 nid = zone_to_nid(*z);
84 if (cpuset_zone_allowed_softwall(*z, htlb_alloc_mask) &&
85 !list_empty(&hugepage_freelists[nid])) {
86 page = list_entry(hugepage_freelists[nid].next,
90 free_huge_pages_node[nid]--;
91 if (vma && vma->vm_flags & VM_MAYSHARE)
96 mpol_free(mpol); /* unref if mpol !NULL */
100 static void update_and_free_page(struct page *page)
104 nr_huge_pages_node[page_to_nid(page)]--;
105 for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
106 page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
107 1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
108 1 << PG_private | 1<< PG_writeback);
110 set_compound_page_dtor(page, NULL);
111 set_page_refcounted(page);
112 __free_pages(page, HUGETLB_PAGE_ORDER);
115 static void free_huge_page(struct page *page)
117 int nid = page_to_nid(page);
119 BUG_ON(page_count(page));
120 INIT_LIST_HEAD(&page->lru);
122 spin_lock(&hugetlb_lock);
123 if (surplus_huge_pages_node[nid]) {
124 update_and_free_page(page);
125 surplus_huge_pages--;
126 surplus_huge_pages_node[nid]--;
128 enqueue_huge_page(page);
130 spin_unlock(&hugetlb_lock);
134 * Increment or decrement surplus_huge_pages. Keep node-specific counters
135 * balanced by operating on them in a round-robin fashion.
136 * Returns 1 if an adjustment was made.
138 static int adjust_pool_surplus(int delta)
144 VM_BUG_ON(delta != -1 && delta != 1);
146 nid = next_node(nid, node_online_map);
147 if (nid == MAX_NUMNODES)
148 nid = first_node(node_online_map);
150 /* To shrink on this node, there must be a surplus page */
151 if (delta < 0 && !surplus_huge_pages_node[nid])
153 /* Surplus cannot exceed the total number of pages */
154 if (delta > 0 && surplus_huge_pages_node[nid] >=
155 nr_huge_pages_node[nid])
158 surplus_huge_pages += delta;
159 surplus_huge_pages_node[nid] += delta;
162 } while (nid != prev_nid);
168 static int alloc_fresh_huge_page(void)
175 * Copy static prev_nid to local nid, work on that, then copy it
176 * back to prev_nid afterwards: otherwise there's a window in which
177 * a racer might pass invalid nid MAX_NUMNODES to alloc_pages_node.
178 * But we don't need to use a spin_lock here: it really doesn't
179 * matter if occasionally a racer chooses the same nid as we do.
181 nid = next_node(prev_nid, node_online_map);
182 if (nid == MAX_NUMNODES)
183 nid = first_node(node_online_map);
186 page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
189 set_compound_page_dtor(page, free_huge_page);
190 spin_lock(&hugetlb_lock);
192 nr_huge_pages_node[page_to_nid(page)]++;
193 spin_unlock(&hugetlb_lock);
194 put_page(page); /* free it into the hugepage allocator */
200 static struct page *alloc_buddy_huge_page(struct vm_area_struct *vma,
201 unsigned long address)
205 /* Check if the dynamic pool is enabled */
206 if (!hugetlb_dynamic_pool)
209 page = alloc_pages(htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
212 set_compound_page_dtor(page, free_huge_page);
213 spin_lock(&hugetlb_lock);
215 nr_huge_pages_node[page_to_nid(page)]++;
216 surplus_huge_pages++;
217 surplus_huge_pages_node[page_to_nid(page)]++;
218 spin_unlock(&hugetlb_lock);
225 * Increase the hugetlb pool such that it can accomodate a reservation
228 static int gather_surplus_pages(int delta)
230 struct list_head surplus_list;
231 struct page *page, *tmp;
233 int needed, allocated;
235 needed = (resv_huge_pages + delta) - free_huge_pages;
240 INIT_LIST_HEAD(&surplus_list);
244 spin_unlock(&hugetlb_lock);
245 for (i = 0; i < needed; i++) {
246 page = alloc_buddy_huge_page(NULL, 0);
249 * We were not able to allocate enough pages to
250 * satisfy the entire reservation so we free what
251 * we've allocated so far.
253 spin_lock(&hugetlb_lock);
258 list_add(&page->lru, &surplus_list);
263 * After retaking hugetlb_lock, we need to recalculate 'needed'
264 * because either resv_huge_pages or free_huge_pages may have changed.
266 spin_lock(&hugetlb_lock);
267 needed = (resv_huge_pages + delta) - (free_huge_pages + allocated);
272 * The surplus_list now contains _at_least_ the number of extra pages
273 * needed to accomodate the reservation. Add the appropriate number
274 * of pages to the hugetlb pool and free the extras back to the buddy
280 list_for_each_entry_safe(page, tmp, &surplus_list, lru) {
281 list_del(&page->lru);
283 enqueue_huge_page(page);
285 update_and_free_page(page);
292 * When releasing a hugetlb pool reservation, any surplus pages that were
293 * allocated to satisfy the reservation must be explicitly freed if they were
296 void return_unused_surplus_pages(unsigned long unused_resv_pages)
300 unsigned long nr_pages;
302 nr_pages = min(unused_resv_pages, surplus_huge_pages);
305 nid = next_node(nid, node_online_map);
306 if (nid == MAX_NUMNODES)
307 nid = first_node(node_online_map);
309 if (!surplus_huge_pages_node[nid])
312 if (!list_empty(&hugepage_freelists[nid])) {
313 page = list_entry(hugepage_freelists[nid].next,
315 list_del(&page->lru);
316 update_and_free_page(page);
318 free_huge_pages_node[nid]--;
319 surplus_huge_pages--;
320 surplus_huge_pages_node[nid]--;
326 static struct page *alloc_huge_page(struct vm_area_struct *vma,
329 struct page *page = NULL;
330 int use_reserved_page = vma->vm_flags & VM_MAYSHARE;
332 spin_lock(&hugetlb_lock);
333 if (!use_reserved_page && (free_huge_pages <= resv_huge_pages))
336 page = dequeue_huge_page(vma, addr);
340 spin_unlock(&hugetlb_lock);
341 set_page_refcounted(page);
345 spin_unlock(&hugetlb_lock);
348 * Private mappings do not use reserved huge pages so the allocation
349 * may have failed due to an undersized hugetlb pool. Try to grab a
350 * surplus huge page from the buddy allocator.
352 if (!use_reserved_page)
353 page = alloc_buddy_huge_page(vma, addr);
358 static int __init hugetlb_init(void)
362 if (HPAGE_SHIFT == 0)
365 for (i = 0; i < MAX_NUMNODES; ++i)
366 INIT_LIST_HEAD(&hugepage_freelists[i]);
368 for (i = 0; i < max_huge_pages; ++i) {
369 if (!alloc_fresh_huge_page())
372 max_huge_pages = free_huge_pages = nr_huge_pages = i;
373 printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
376 module_init(hugetlb_init);
378 static int __init hugetlb_setup(char *s)
380 if (sscanf(s, "%lu", &max_huge_pages) <= 0)
384 __setup("hugepages=", hugetlb_setup);
386 static unsigned int cpuset_mems_nr(unsigned int *array)
391 for_each_node_mask(node, cpuset_current_mems_allowed)
398 #ifdef CONFIG_HIGHMEM
399 static void try_to_free_low(unsigned long count)
403 for (i = 0; i < MAX_NUMNODES; ++i) {
404 struct page *page, *next;
405 list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
406 if (PageHighMem(page))
408 list_del(&page->lru);
409 update_and_free_page(page);
411 free_huge_pages_node[page_to_nid(page)]--;
412 if (count >= nr_huge_pages)
418 static inline void try_to_free_low(unsigned long count)
423 #define persistent_huge_pages (nr_huge_pages - surplus_huge_pages)
424 static unsigned long set_max_huge_pages(unsigned long count)
426 unsigned long min_count, ret;
429 * Increase the pool size
430 * First take pages out of surplus state. Then make up the
431 * remaining difference by allocating fresh huge pages.
433 spin_lock(&hugetlb_lock);
434 while (surplus_huge_pages && count > persistent_huge_pages) {
435 if (!adjust_pool_surplus(-1))
439 while (count > persistent_huge_pages) {
442 * If this allocation races such that we no longer need the
443 * page, free_huge_page will handle it by freeing the page
444 * and reducing the surplus.
446 spin_unlock(&hugetlb_lock);
447 ret = alloc_fresh_huge_page();
448 spin_lock(&hugetlb_lock);
453 if (count >= persistent_huge_pages)
457 * Decrease the pool size
458 * First return free pages to the buddy allocator (being careful
459 * to keep enough around to satisfy reservations). Then place
460 * pages into surplus state as needed so the pool will shrink
461 * to the desired size as pages become free.
463 min_count = max(count, resv_huge_pages);
464 try_to_free_low(min_count);
465 while (min_count < persistent_huge_pages) {
466 struct page *page = dequeue_huge_page(NULL, 0);
469 update_and_free_page(page);
471 while (count < persistent_huge_pages) {
472 if (!adjust_pool_surplus(1))
476 ret = persistent_huge_pages;
477 spin_unlock(&hugetlb_lock);
481 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
482 struct file *file, void __user *buffer,
483 size_t *length, loff_t *ppos)
485 proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
486 max_huge_pages = set_max_huge_pages(max_huge_pages);
490 int hugetlb_treat_movable_handler(struct ctl_table *table, int write,
491 struct file *file, void __user *buffer,
492 size_t *length, loff_t *ppos)
494 proc_dointvec(table, write, file, buffer, length, ppos);
495 if (hugepages_treat_as_movable)
496 htlb_alloc_mask = GFP_HIGHUSER_MOVABLE;
498 htlb_alloc_mask = GFP_HIGHUSER;
502 #endif /* CONFIG_SYSCTL */
504 int hugetlb_report_meminfo(char *buf)
507 "HugePages_Total: %5lu\n"
508 "HugePages_Free: %5lu\n"
509 "HugePages_Rsvd: %5lu\n"
510 "HugePages_Surp: %5lu\n"
511 "Hugepagesize: %5lu kB\n",
519 int hugetlb_report_node_meminfo(int nid, char *buf)
522 "Node %d HugePages_Total: %5u\n"
523 "Node %d HugePages_Free: %5u\n",
524 nid, nr_huge_pages_node[nid],
525 nid, free_huge_pages_node[nid]);
528 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
529 unsigned long hugetlb_total_pages(void)
531 return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
535 * We cannot handle pagefaults against hugetlb pages at all. They cause
536 * handle_mm_fault() to try to instantiate regular-sized pages in the
537 * hugegpage VMA. do_page_fault() is supposed to trap this, so BUG is we get
540 static int hugetlb_vm_op_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
546 struct vm_operations_struct hugetlb_vm_ops = {
547 .fault = hugetlb_vm_op_fault,
550 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
557 pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
559 entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
561 entry = pte_mkyoung(entry);
562 entry = pte_mkhuge(entry);
567 static void set_huge_ptep_writable(struct vm_area_struct *vma,
568 unsigned long address, pte_t *ptep)
572 entry = pte_mkwrite(pte_mkdirty(*ptep));
573 if (ptep_set_access_flags(vma, address, ptep, entry, 1)) {
574 update_mmu_cache(vma, address, entry);
579 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
580 struct vm_area_struct *vma)
582 pte_t *src_pte, *dst_pte, entry;
583 struct page *ptepage;
587 cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
589 for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
590 src_pte = huge_pte_offset(src, addr);
593 dst_pte = huge_pte_alloc(dst, addr);
596 spin_lock(&dst->page_table_lock);
597 spin_lock(&src->page_table_lock);
598 if (!pte_none(*src_pte)) {
600 ptep_set_wrprotect(src, addr, src_pte);
602 ptepage = pte_page(entry);
604 set_huge_pte_at(dst, addr, dst_pte, entry);
606 spin_unlock(&src->page_table_lock);
607 spin_unlock(&dst->page_table_lock);
615 void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
618 struct mm_struct *mm = vma->vm_mm;
619 unsigned long address;
625 * A page gathering list, protected by per file i_mmap_lock. The
626 * lock is used to avoid list corruption from multiple unmapping
627 * of the same page since we are using page->lru.
629 LIST_HEAD(page_list);
631 WARN_ON(!is_vm_hugetlb_page(vma));
632 BUG_ON(start & ~HPAGE_MASK);
633 BUG_ON(end & ~HPAGE_MASK);
635 spin_lock(&mm->page_table_lock);
636 for (address = start; address < end; address += HPAGE_SIZE) {
637 ptep = huge_pte_offset(mm, address);
641 if (huge_pmd_unshare(mm, &address, ptep))
644 pte = huge_ptep_get_and_clear(mm, address, ptep);
648 page = pte_page(pte);
650 set_page_dirty(page);
651 list_add(&page->lru, &page_list);
653 spin_unlock(&mm->page_table_lock);
654 flush_tlb_range(vma, start, end);
655 list_for_each_entry_safe(page, tmp, &page_list, lru) {
656 list_del(&page->lru);
661 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
665 * It is undesirable to test vma->vm_file as it should be non-null
666 * for valid hugetlb area. However, vm_file will be NULL in the error
667 * cleanup path of do_mmap_pgoff. When hugetlbfs ->mmap method fails,
668 * do_mmap_pgoff() nullifies vma->vm_file before calling this function
669 * to clean up. Since no pte has actually been setup, it is safe to
670 * do nothing in this case.
673 spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
674 __unmap_hugepage_range(vma, start, end);
675 spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
679 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
680 unsigned long address, pte_t *ptep, pte_t pte)
682 struct page *old_page, *new_page;
685 old_page = pte_page(pte);
687 /* If no-one else is actually using this page, avoid the copy
688 * and just make the page writable */
689 avoidcopy = (page_count(old_page) == 1);
691 set_huge_ptep_writable(vma, address, ptep);
695 page_cache_get(old_page);
696 new_page = alloc_huge_page(vma, address);
699 page_cache_release(old_page);
703 spin_unlock(&mm->page_table_lock);
704 copy_huge_page(new_page, old_page, address, vma);
705 spin_lock(&mm->page_table_lock);
707 ptep = huge_pte_offset(mm, address & HPAGE_MASK);
708 if (likely(pte_same(*ptep, pte))) {
710 set_huge_pte_at(mm, address, ptep,
711 make_huge_pte(vma, new_page, 1));
712 /* Make the old page be freed below */
715 page_cache_release(new_page);
716 page_cache_release(old_page);
720 static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
721 unsigned long address, pte_t *ptep, int write_access)
723 int ret = VM_FAULT_SIGBUS;
727 struct address_space *mapping;
730 mapping = vma->vm_file->f_mapping;
731 idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
732 + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
735 * Use page lock to guard against racing truncation
736 * before we get page_table_lock.
739 page = find_lock_page(mapping, idx);
741 size = i_size_read(mapping->host) >> HPAGE_SHIFT;
744 if (hugetlb_get_quota(mapping))
746 page = alloc_huge_page(vma, address);
748 hugetlb_put_quota(mapping);
752 clear_huge_page(page, address);
754 if (vma->vm_flags & VM_SHARED) {
757 err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
760 hugetlb_put_quota(mapping);
769 spin_lock(&mm->page_table_lock);
770 size = i_size_read(mapping->host) >> HPAGE_SHIFT;
775 if (!pte_none(*ptep))
778 new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
779 && (vma->vm_flags & VM_SHARED)));
780 set_huge_pte_at(mm, address, ptep, new_pte);
782 if (write_access && !(vma->vm_flags & VM_SHARED)) {
783 /* Optimization, do the COW without a second fault */
784 ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
787 spin_unlock(&mm->page_table_lock);
793 spin_unlock(&mm->page_table_lock);
794 hugetlb_put_quota(mapping);
800 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
801 unsigned long address, int write_access)
806 static DEFINE_MUTEX(hugetlb_instantiation_mutex);
808 ptep = huge_pte_alloc(mm, address);
813 * Serialize hugepage allocation and instantiation, so that we don't
814 * get spurious allocation failures if two CPUs race to instantiate
815 * the same page in the page cache.
817 mutex_lock(&hugetlb_instantiation_mutex);
819 if (pte_none(entry)) {
820 ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
821 mutex_unlock(&hugetlb_instantiation_mutex);
827 spin_lock(&mm->page_table_lock);
828 /* Check for a racing update before calling hugetlb_cow */
829 if (likely(pte_same(entry, *ptep)))
830 if (write_access && !pte_write(entry))
831 ret = hugetlb_cow(mm, vma, address, ptep, entry);
832 spin_unlock(&mm->page_table_lock);
833 mutex_unlock(&hugetlb_instantiation_mutex);
838 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
839 struct page **pages, struct vm_area_struct **vmas,
840 unsigned long *position, int *length, int i)
842 unsigned long pfn_offset;
843 unsigned long vaddr = *position;
844 int remainder = *length;
846 spin_lock(&mm->page_table_lock);
847 while (vaddr < vma->vm_end && remainder) {
852 * Some archs (sparc64, sh*) have multiple pte_ts to
853 * each hugepage. We have to make * sure we get the
854 * first, for the page indexing below to work.
856 pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
858 if (!pte || pte_none(*pte)) {
861 spin_unlock(&mm->page_table_lock);
862 ret = hugetlb_fault(mm, vma, vaddr, 0);
863 spin_lock(&mm->page_table_lock);
864 if (!(ret & VM_FAULT_ERROR))
873 pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
874 page = pte_page(*pte);
878 pages[i] = page + pfn_offset;
888 if (vaddr < vma->vm_end && remainder &&
889 pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
891 * We use pfn_offset to avoid touching the pageframes
892 * of this compound page.
897 spin_unlock(&mm->page_table_lock);
904 void hugetlb_change_protection(struct vm_area_struct *vma,
905 unsigned long address, unsigned long end, pgprot_t newprot)
907 struct mm_struct *mm = vma->vm_mm;
908 unsigned long start = address;
912 BUG_ON(address >= end);
913 flush_cache_range(vma, address, end);
915 spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
916 spin_lock(&mm->page_table_lock);
917 for (; address < end; address += HPAGE_SIZE) {
918 ptep = huge_pte_offset(mm, address);
921 if (huge_pmd_unshare(mm, &address, ptep))
923 if (!pte_none(*ptep)) {
924 pte = huge_ptep_get_and_clear(mm, address, ptep);
925 pte = pte_mkhuge(pte_modify(pte, newprot));
926 set_huge_pte_at(mm, address, ptep, pte);
929 spin_unlock(&mm->page_table_lock);
930 spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
932 flush_tlb_range(vma, start, end);
936 struct list_head link;
941 static long region_add(struct list_head *head, long f, long t)
943 struct file_region *rg, *nrg, *trg;
945 /* Locate the region we are either in or before. */
946 list_for_each_entry(rg, head, link)
950 /* Round our left edge to the current segment if it encloses us. */
954 /* Check for and consume any regions we now overlap with. */
956 list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
957 if (&rg->link == head)
962 /* If this area reaches higher then extend our area to
963 * include it completely. If this is not the first area
964 * which we intend to reuse, free it. */
977 static long region_chg(struct list_head *head, long f, long t)
979 struct file_region *rg, *nrg;
982 /* Locate the region we are before or in. */
983 list_for_each_entry(rg, head, link)
987 /* If we are below the current region then a new region is required.
988 * Subtle, allocate a new region at the position but make it zero
989 * size such that we can guarentee to record the reservation. */
990 if (&rg->link == head || t < rg->from) {
991 nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
996 INIT_LIST_HEAD(&nrg->link);
997 list_add(&nrg->link, rg->link.prev);
1002 /* Round our left edge to the current segment if it encloses us. */
1007 /* Check for and consume any regions we now overlap with. */
1008 list_for_each_entry(rg, rg->link.prev, link) {
1009 if (&rg->link == head)
1014 /* We overlap with this area, if it extends futher than
1015 * us then we must extend ourselves. Account for its
1016 * existing reservation. */
1021 chg -= rg->to - rg->from;
1026 static long region_truncate(struct list_head *head, long end)
1028 struct file_region *rg, *trg;
1031 /* Locate the region we are either in or before. */
1032 list_for_each_entry(rg, head, link)
1035 if (&rg->link == head)
1038 /* If we are in the middle of a region then adjust it. */
1039 if (end > rg->from) {
1042 rg = list_entry(rg->link.next, typeof(*rg), link);
1045 /* Drop any remaining regions. */
1046 list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
1047 if (&rg->link == head)
1049 chg += rg->to - rg->from;
1050 list_del(&rg->link);
1056 static int hugetlb_acct_memory(long delta)
1060 spin_lock(&hugetlb_lock);
1062 * When cpuset is configured, it breaks the strict hugetlb page
1063 * reservation as the accounting is done on a global variable. Such
1064 * reservation is completely rubbish in the presence of cpuset because
1065 * the reservation is not checked against page availability for the
1066 * current cpuset. Application can still potentially OOM'ed by kernel
1067 * with lack of free htlb page in cpuset that the task is in.
1068 * Attempt to enforce strict accounting with cpuset is almost
1069 * impossible (or too ugly) because cpuset is too fluid that
1070 * task or memory node can be dynamically moved between cpusets.
1072 * The change of semantics for shared hugetlb mapping with cpuset is
1073 * undesirable. However, in order to preserve some of the semantics,
1074 * we fall back to check against current free page availability as
1075 * a best attempt and hopefully to minimize the impact of changing
1076 * semantics that cpuset has.
1079 if (gather_surplus_pages(delta) < 0)
1082 if (delta > cpuset_mems_nr(free_huge_pages_node))
1087 resv_huge_pages += delta;
1089 return_unused_surplus_pages((unsigned long) -delta);
1092 spin_unlock(&hugetlb_lock);
1096 int hugetlb_reserve_pages(struct inode *inode, long from, long to)
1100 chg = region_chg(&inode->i_mapping->private_list, from, to);
1104 ret = hugetlb_acct_memory(chg);
1107 region_add(&inode->i_mapping->private_list, from, to);
1111 void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
1113 long chg = region_truncate(&inode->i_mapping->private_list, offset);
1114 hugetlb_acct_memory(freed - chg);