hugetlb.c revision 9de455b20705f36384a711d4a20bcf7ba1ab180b 
1/*
2 * Generic hugetlb support.
3 * (C) William Irwin, April 2004
4 */
5#include <linux/gfp.h>
6#include <linux/list.h>
7#include <linux/init.h>
8#include <linux/module.h>
9#include <linux/mm.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>
17
18#include <asm/page.h>
19#include <asm/pgtable.h>
20
21#include <linux/hugetlb.h>
22#include "internal.h"
23
24const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
25static unsigned long nr_huge_pages, free_huge_pages, resv_huge_pages;
26unsigned long max_huge_pages;
27static struct list_head hugepage_freelists[MAX_NUMNODES];
28static unsigned int nr_huge_pages_node[MAX_NUMNODES];
29static unsigned int free_huge_pages_node[MAX_NUMNODES];
30/*
31 * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
32 */
33static DEFINE_SPINLOCK(hugetlb_lock);
34
35static void clear_huge_page(struct page *page, unsigned long addr)
36{
37	int i;
38
39	might_sleep();
40	for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
41		cond_resched();
42		clear_user_highpage(page + i, addr);
43	}
44}
45
46static void copy_huge_page(struct page *dst, struct page *src,
47			   unsigned long addr, struct vm_area_struct *vma)
48{
49	int i;
50
51	might_sleep();
52	for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) {
53		cond_resched();
54		copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
55	}
56}
57
58static void enqueue_huge_page(struct page *page)
59{
60	int nid = page_to_nid(page);
61	list_add(&page->lru, &hugepage_freelists[nid]);
62	free_huge_pages++;
63	free_huge_pages_node[nid]++;
64}
65
66static struct page *dequeue_huge_page(struct vm_area_struct *vma,
67				unsigned long address)
68{
69	int nid = numa_node_id();
70	struct page *page = NULL;
71	struct zonelist *zonelist = huge_zonelist(vma, address);
72	struct zone **z;
73
74	for (z = zonelist->zones; *z; z++) {
75		nid = zone_to_nid(*z);
76		if (cpuset_zone_allowed_softwall(*z, GFP_HIGHUSER) &&
77		    !list_empty(&hugepage_freelists[nid]))
78			break;
79	}
80
81	if (*z) {
82		page = list_entry(hugepage_freelists[nid].next,
83				  struct page, lru);
84		list_del(&page->lru);
85		free_huge_pages--;
86		free_huge_pages_node[nid]--;
87	}
88	return page;
89}
90
91static void free_huge_page(struct page *page)
92{
93	BUG_ON(page_count(page));
94
95	INIT_LIST_HEAD(&page->lru);
96
97	spin_lock(&hugetlb_lock);
98	enqueue_huge_page(page);
99	spin_unlock(&hugetlb_lock);
100}
101
102static int alloc_fresh_huge_page(void)
103{
104	static int nid = 0;
105	struct page *page;
106	page = alloc_pages_node(nid, GFP_HIGHUSER|__GFP_COMP|__GFP_NOWARN,
107					HUGETLB_PAGE_ORDER);
108	nid = next_node(nid, node_online_map);
109	if (nid == MAX_NUMNODES)
110		nid = first_node(node_online_map);
111	if (page) {
112		set_compound_page_dtor(page, free_huge_page);
113		spin_lock(&hugetlb_lock);
114		nr_huge_pages++;
115		nr_huge_pages_node[page_to_nid(page)]++;
116		spin_unlock(&hugetlb_lock);
117		put_page(page); /* free it into the hugepage allocator */
118		return 1;
119	}
120	return 0;
121}
122
123static struct page *alloc_huge_page(struct vm_area_struct *vma,
124				    unsigned long addr)
125{
126	struct page *page;
127
128	spin_lock(&hugetlb_lock);
129	if (vma->vm_flags & VM_MAYSHARE)
130		resv_huge_pages--;
131	else if (free_huge_pages <= resv_huge_pages)
132		goto fail;
133
134	page = dequeue_huge_page(vma, addr);
135	if (!page)
136		goto fail;
137
138	spin_unlock(&hugetlb_lock);
139	set_page_refcounted(page);
140	return page;
141
142fail:
143	spin_unlock(&hugetlb_lock);
144	return NULL;
145}
146
147static int __init hugetlb_init(void)
148{
149	unsigned long i;
150
151	if (HPAGE_SHIFT == 0)
152		return 0;
153
154	for (i = 0; i < MAX_NUMNODES; ++i)
155		INIT_LIST_HEAD(&hugepage_freelists[i]);
156
157	for (i = 0; i < max_huge_pages; ++i) {
158		if (!alloc_fresh_huge_page())
159			break;
160	}
161	max_huge_pages = free_huge_pages = nr_huge_pages = i;
162	printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
163	return 0;
164}
165module_init(hugetlb_init);
166
167static int __init hugetlb_setup(char *s)
168{
169	if (sscanf(s, "%lu", &max_huge_pages) <= 0)
170		max_huge_pages = 0;
171	return 1;
172}
173__setup("hugepages=", hugetlb_setup);
174
175#ifdef CONFIG_SYSCTL
176static void update_and_free_page(struct page *page)
177{
178	int i;
179	nr_huge_pages--;
180	nr_huge_pages_node[page_to_nid(page)]--;
181	for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
182		page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
183				1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
184				1 << PG_private | 1<< PG_writeback);
185	}
186	page[1].lru.next = NULL;
187	set_page_refcounted(page);
188	__free_pages(page, HUGETLB_PAGE_ORDER);
189}
190
191#ifdef CONFIG_HIGHMEM
192static void try_to_free_low(unsigned long count)
193{
194	int i;
195
196	for (i = 0; i < MAX_NUMNODES; ++i) {
197		struct page *page, *next;
198		list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
199			if (PageHighMem(page))
200				continue;
201			list_del(&page->lru);
202			update_and_free_page(page);
203			free_huge_pages--;
204			free_huge_pages_node[page_to_nid(page)]--;
205			if (count >= nr_huge_pages)
206				return;
207		}
208	}
209}
210#else
211static inline void try_to_free_low(unsigned long count)
212{
213}
214#endif
215
216static unsigned long set_max_huge_pages(unsigned long count)
217{
218	while (count > nr_huge_pages) {
219		if (!alloc_fresh_huge_page())
220			return nr_huge_pages;
221	}
222	if (count >= nr_huge_pages)
223		return nr_huge_pages;
224
225	spin_lock(&hugetlb_lock);
226	count = max(count, resv_huge_pages);
227	try_to_free_low(count);
228	while (count < nr_huge_pages) {
229		struct page *page = dequeue_huge_page(NULL, 0);
230		if (!page)
231			break;
232		update_and_free_page(page);
233	}
234	spin_unlock(&hugetlb_lock);
235	return nr_huge_pages;
236}
237
238int hugetlb_sysctl_handler(struct ctl_table *table, int write,
239			   struct file *file, void __user *buffer,
240			   size_t *length, loff_t *ppos)
241{
242	proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
243	max_huge_pages = set_max_huge_pages(max_huge_pages);
244	return 0;
245}
246#endif /* CONFIG_SYSCTL */
247
248int hugetlb_report_meminfo(char *buf)
249{
250	return sprintf(buf,
251			"HugePages_Total: %5lu\n"
252			"HugePages_Free:  %5lu\n"
253			"HugePages_Rsvd:  %5lu\n"
254			"Hugepagesize:    %5lu kB\n",
255			nr_huge_pages,
256			free_huge_pages,
257			resv_huge_pages,
258			HPAGE_SIZE/1024);
259}
260
261int hugetlb_report_node_meminfo(int nid, char *buf)
262{
263	return sprintf(buf,
264		"Node %d HugePages_Total: %5u\n"
265		"Node %d HugePages_Free:  %5u\n",
266		nid, nr_huge_pages_node[nid],
267		nid, free_huge_pages_node[nid]);
268}
269
270/* Return the number pages of memory we physically have, in PAGE_SIZE units. */
271unsigned long hugetlb_total_pages(void)
272{
273	return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
274}
275
276/*
277 * We cannot handle pagefaults against hugetlb pages at all.  They cause
278 * handle_mm_fault() to try to instantiate regular-sized pages in the
279 * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
280 * this far.
281 */
282static struct page *hugetlb_nopage(struct vm_area_struct *vma,
283				unsigned long address, int *unused)
284{
285	BUG();
286	return NULL;
287}
288
289struct vm_operations_struct hugetlb_vm_ops = {
290	.nopage = hugetlb_nopage,
291};
292
293static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
294				int writable)
295{
296	pte_t entry;
297
298	if (writable) {
299		entry =
300		    pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
301	} else {
302		entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
303	}
304	entry = pte_mkyoung(entry);
305	entry = pte_mkhuge(entry);
306
307	return entry;
308}
309
310static void set_huge_ptep_writable(struct vm_area_struct *vma,
311				   unsigned long address, pte_t *ptep)
312{
313	pte_t entry;
314
315	entry = pte_mkwrite(pte_mkdirty(*ptep));
316	ptep_set_access_flags(vma, address, ptep, entry, 1);
317	update_mmu_cache(vma, address, entry);
318	lazy_mmu_prot_update(entry);
319}
320
321
322int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
323			    struct vm_area_struct *vma)
324{
325	pte_t *src_pte, *dst_pte, entry;
326	struct page *ptepage;
327	unsigned long addr;
328	int cow;
329
330	cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
331
332	for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
333		src_pte = huge_pte_offset(src, addr);
334		if (!src_pte)
335			continue;
336		dst_pte = huge_pte_alloc(dst, addr);
337		if (!dst_pte)
338			goto nomem;
339		spin_lock(&dst->page_table_lock);
340		spin_lock(&src->page_table_lock);
341		if (!pte_none(*src_pte)) {
342			if (cow)
343				ptep_set_wrprotect(src, addr, src_pte);
344			entry = *src_pte;
345			ptepage = pte_page(entry);
346			get_page(ptepage);
347			set_huge_pte_at(dst, addr, dst_pte, entry);
348		}
349		spin_unlock(&src->page_table_lock);
350		spin_unlock(&dst->page_table_lock);
351	}
352	return 0;
353
354nomem:
355	return -ENOMEM;
356}
357
358void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
359			    unsigned long end)
360{
361	struct mm_struct *mm = vma->vm_mm;
362	unsigned long address;
363	pte_t *ptep;
364	pte_t pte;
365	struct page *page;
366	struct page *tmp;
367	/*
368	 * A page gathering list, protected by per file i_mmap_lock. The
369	 * lock is used to avoid list corruption from multiple unmapping
370	 * of the same page since we are using page->lru.
371	 */
372	LIST_HEAD(page_list);
373
374	WARN_ON(!is_vm_hugetlb_page(vma));
375	BUG_ON(start & ~HPAGE_MASK);
376	BUG_ON(end & ~HPAGE_MASK);
377
378	spin_lock(&mm->page_table_lock);
379	for (address = start; address < end; address += HPAGE_SIZE) {
380		ptep = huge_pte_offset(mm, address);
381		if (!ptep)
382			continue;
383
384		if (huge_pmd_unshare(mm, &address, ptep))
385			continue;
386
387		pte = huge_ptep_get_and_clear(mm, address, ptep);
388		if (pte_none(pte))
389			continue;
390
391		page = pte_page(pte);
392		list_add(&page->lru, &page_list);
393	}
394	spin_unlock(&mm->page_table_lock);
395	flush_tlb_range(vma, start, end);
396	list_for_each_entry_safe(page, tmp, &page_list, lru) {
397		list_del(&page->lru);
398		put_page(page);
399	}
400}
401
402void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
403			  unsigned long end)
404{
405	/*
406	 * It is undesirable to test vma->vm_file as it should be non-null
407	 * for valid hugetlb area. However, vm_file will be NULL in the error
408	 * cleanup path of do_mmap_pgoff. When hugetlbfs ->mmap method fails,
409	 * do_mmap_pgoff() nullifies vma->vm_file before calling this function
410	 * to clean up. Since no pte has actually been setup, it is safe to
411	 * do nothing in this case.
412	 */
413	if (vma->vm_file) {
414		spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
415		__unmap_hugepage_range(vma, start, end);
416		spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
417	}
418}
419
420static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
421			unsigned long address, pte_t *ptep, pte_t pte)
422{
423	struct page *old_page, *new_page;
424	int avoidcopy;
425
426	old_page = pte_page(pte);
427
428	/* If no-one else is actually using this page, avoid the copy
429	 * and just make the page writable */
430	avoidcopy = (page_count(old_page) == 1);
431	if (avoidcopy) {
432		set_huge_ptep_writable(vma, address, ptep);
433		return VM_FAULT_MINOR;
434	}
435
436	page_cache_get(old_page);
437	new_page = alloc_huge_page(vma, address);
438
439	if (!new_page) {
440		page_cache_release(old_page);
441		return VM_FAULT_OOM;
442	}
443
444	spin_unlock(&mm->page_table_lock);
445	copy_huge_page(new_page, old_page, address, vma);
446	spin_lock(&mm->page_table_lock);
447
448	ptep = huge_pte_offset(mm, address & HPAGE_MASK);
449	if (likely(pte_same(*ptep, pte))) {
450		/* Break COW */
451		set_huge_pte_at(mm, address, ptep,
452				make_huge_pte(vma, new_page, 1));
453		/* Make the old page be freed below */
454		new_page = old_page;
455	}
456	page_cache_release(new_page);
457	page_cache_release(old_page);
458	return VM_FAULT_MINOR;
459}
460
461int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
462			unsigned long address, pte_t *ptep, int write_access)
463{
464	int ret = VM_FAULT_SIGBUS;
465	unsigned long idx;
466	unsigned long size;
467	struct page *page;
468	struct address_space *mapping;
469	pte_t new_pte;
470
471	mapping = vma->vm_file->f_mapping;
472	idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
473		+ (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
474
475	/*
476	 * Use page lock to guard against racing truncation
477	 * before we get page_table_lock.
478	 */
479retry:
480	page = find_lock_page(mapping, idx);
481	if (!page) {
482		size = i_size_read(mapping->host) >> HPAGE_SHIFT;
483		if (idx >= size)
484			goto out;
485		if (hugetlb_get_quota(mapping))
486			goto out;
487		page = alloc_huge_page(vma, address);
488		if (!page) {
489			hugetlb_put_quota(mapping);
490			ret = VM_FAULT_OOM;
491			goto out;
492		}
493		clear_huge_page(page, address);
494
495		if (vma->vm_flags & VM_SHARED) {
496			int err;
497
498			err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
499			if (err) {
500				put_page(page);
501				hugetlb_put_quota(mapping);
502				if (err == -EEXIST)
503					goto retry;
504				goto out;
505			}
506		} else
507			lock_page(page);
508	}
509
510	spin_lock(&mm->page_table_lock);
511	size = i_size_read(mapping->host) >> HPAGE_SHIFT;
512	if (idx >= size)
513		goto backout;
514
515	ret = VM_FAULT_MINOR;
516	if (!pte_none(*ptep))
517		goto backout;
518
519	new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
520				&& (vma->vm_flags & VM_SHARED)));
521	set_huge_pte_at(mm, address, ptep, new_pte);
522
523	if (write_access && !(vma->vm_flags & VM_SHARED)) {
524		/* Optimization, do the COW without a second fault */
525		ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
526	}
527
528	spin_unlock(&mm->page_table_lock);
529	unlock_page(page);
530out:
531	return ret;
532
533backout:
534	spin_unlock(&mm->page_table_lock);
535	hugetlb_put_quota(mapping);
536	unlock_page(page);
537	put_page(page);
538	goto out;
539}
540
541int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
542			unsigned long address, int write_access)
543{
544	pte_t *ptep;
545	pte_t entry;
546	int ret;
547	static DEFINE_MUTEX(hugetlb_instantiation_mutex);
548
549	ptep = huge_pte_alloc(mm, address);
550	if (!ptep)
551		return VM_FAULT_OOM;
552
553	/*
554	 * Serialize hugepage allocation and instantiation, so that we don't
555	 * get spurious allocation failures if two CPUs race to instantiate
556	 * the same page in the page cache.
557	 */
558	mutex_lock(&hugetlb_instantiation_mutex);
559	entry = *ptep;
560	if (pte_none(entry)) {
561		ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
562		mutex_unlock(&hugetlb_instantiation_mutex);
563		return ret;
564	}
565
566	ret = VM_FAULT_MINOR;
567
568	spin_lock(&mm->page_table_lock);
569	/* Check for a racing update before calling hugetlb_cow */
570	if (likely(pte_same(entry, *ptep)))
571		if (write_access && !pte_write(entry))
572			ret = hugetlb_cow(mm, vma, address, ptep, entry);
573	spin_unlock(&mm->page_table_lock);
574	mutex_unlock(&hugetlb_instantiation_mutex);
575
576	return ret;
577}
578
579int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
580			struct page **pages, struct vm_area_struct **vmas,
581			unsigned long *position, int *length, int i)
582{
583	unsigned long pfn_offset;
584	unsigned long vaddr = *position;
585	int remainder = *length;
586
587	spin_lock(&mm->page_table_lock);
588	while (vaddr < vma->vm_end && remainder) {
589		pte_t *pte;
590		struct page *page;
591
592		/*
593		 * Some archs (sparc64, sh*) have multiple pte_ts to
594		 * each hugepage.  We have to make * sure we get the
595		 * first, for the page indexing below to work.
596		 */
597		pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
598
599		if (!pte || pte_none(*pte)) {
600			int ret;
601
602			spin_unlock(&mm->page_table_lock);
603			ret = hugetlb_fault(mm, vma, vaddr, 0);
604			spin_lock(&mm->page_table_lock);
605			if (ret == VM_FAULT_MINOR)
606				continue;
607
608			remainder = 0;
609			if (!i)
610				i = -EFAULT;
611			break;
612		}
613
614		pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
615		page = pte_page(*pte);
616same_page:
617		if (pages) {
618			get_page(page);
619			pages[i] = page + pfn_offset;
620		}
621
622		if (vmas)
623			vmas[i] = vma;
624
625		vaddr += PAGE_SIZE;
626		++pfn_offset;
627		--remainder;
628		++i;
629		if (vaddr < vma->vm_end && remainder &&
630				pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
631			/*
632			 * We use pfn_offset to avoid touching the pageframes
633			 * of this compound page.
634			 */
635			goto same_page;
636		}
637	}
638	spin_unlock(&mm->page_table_lock);
639	*length = remainder;
640	*position = vaddr;
641
642	return i;
643}
644
645void hugetlb_change_protection(struct vm_area_struct *vma,
646		unsigned long address, unsigned long end, pgprot_t newprot)
647{
648	struct mm_struct *mm = vma->vm_mm;
649	unsigned long start = address;
650	pte_t *ptep;
651	pte_t pte;
652
653	BUG_ON(address >= end);
654	flush_cache_range(vma, address, end);
655
656	spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
657	spin_lock(&mm->page_table_lock);
658	for (; address < end; address += HPAGE_SIZE) {
659		ptep = huge_pte_offset(mm, address);
660		if (!ptep)
661			continue;
662		if (huge_pmd_unshare(mm, &address, ptep))
663			continue;
664		if (!pte_none(*ptep)) {
665			pte = huge_ptep_get_and_clear(mm, address, ptep);
666			pte = pte_mkhuge(pte_modify(pte, newprot));
667			set_huge_pte_at(mm, address, ptep, pte);
668			lazy_mmu_prot_update(pte);
669		}
670	}
671	spin_unlock(&mm->page_table_lock);
672	spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
673
674	flush_tlb_range(vma, start, end);
675}
676
677struct file_region {
678	struct list_head link;
679	long from;
680	long to;
681};
682
683static long region_add(struct list_head *head, long f, long t)
684{
685	struct file_region *rg, *nrg, *trg;
686
687	/* Locate the region we are either in or before. */
688	list_for_each_entry(rg, head, link)
689		if (f <= rg->to)
690			break;
691
692	/* Round our left edge to the current segment if it encloses us. */
693	if (f > rg->from)
694		f = rg->from;
695
696	/* Check for and consume any regions we now overlap with. */
697	nrg = rg;
698	list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
699		if (&rg->link == head)
700			break;
701		if (rg->from > t)
702			break;
703
704		/* If this area reaches higher then extend our area to
705		 * include it completely.  If this is not the first area
706		 * which we intend to reuse, free it. */
707		if (rg->to > t)
708			t = rg->to;
709		if (rg != nrg) {
710			list_del(&rg->link);
711			kfree(rg);
712		}
713	}
714	nrg->from = f;
715	nrg->to = t;
716	return 0;
717}
718
719static long region_chg(struct list_head *head, long f, long t)
720{
721	struct file_region *rg, *nrg;
722	long chg = 0;
723
724	/* Locate the region we are before or in. */
725	list_for_each_entry(rg, head, link)
726		if (f <= rg->to)
727			break;
728
729	/* If we are below the current region then a new region is required.
730	 * Subtle, allocate a new region at the position but make it zero
731	 * size such that we can guarentee to record the reservation. */
732	if (&rg->link == head || t < rg->from) {
733		nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
734		if (nrg == 0)
735			return -ENOMEM;
736		nrg->from = f;
737		nrg->to   = f;
738		INIT_LIST_HEAD(&nrg->link);
739		list_add(&nrg->link, rg->link.prev);
740
741		return t - f;
742	}
743
744	/* Round our left edge to the current segment if it encloses us. */
745	if (f > rg->from)
746		f = rg->from;
747	chg = t - f;
748
749	/* Check for and consume any regions we now overlap with. */
750	list_for_each_entry(rg, rg->link.prev, link) {
751		if (&rg->link == head)
752			break;
753		if (rg->from > t)
754			return chg;
755
756		/* We overlap with this area, if it extends futher than
757		 * us then we must extend ourselves.  Account for its
758		 * existing reservation. */
759		if (rg->to > t) {
760			chg += rg->to - t;
761			t = rg->to;
762		}
763		chg -= rg->to - rg->from;
764	}
765	return chg;
766}
767
768static long region_truncate(struct list_head *head, long end)
769{
770	struct file_region *rg, *trg;
771	long chg = 0;
772
773	/* Locate the region we are either in or before. */
774	list_for_each_entry(rg, head, link)
775		if (end <= rg->to)
776			break;
777	if (&rg->link == head)
778		return 0;
779
780	/* If we are in the middle of a region then adjust it. */
781	if (end > rg->from) {
782		chg = rg->to - end;
783		rg->to = end;
784		rg = list_entry(rg->link.next, typeof(*rg), link);
785	}
786
787	/* Drop any remaining regions. */
788	list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
789		if (&rg->link == head)
790			break;
791		chg += rg->to - rg->from;
792		list_del(&rg->link);
793		kfree(rg);
794	}
795	return chg;
796}
797
798static int hugetlb_acct_memory(long delta)
799{
800	int ret = -ENOMEM;
801
802	spin_lock(&hugetlb_lock);
803	if ((delta + resv_huge_pages) <= free_huge_pages) {
804		resv_huge_pages += delta;
805		ret = 0;
806	}
807	spin_unlock(&hugetlb_lock);
808	return ret;
809}
810
811int hugetlb_reserve_pages(struct inode *inode, long from, long to)
812{
813	long ret, chg;
814
815	chg = region_chg(&inode->i_mapping->private_list, from, to);
816	if (chg < 0)
817		return chg;
818	ret = hugetlb_acct_memory(chg);
819	if (ret < 0)
820		return ret;
821	region_add(&inode->i_mapping->private_list, from, to);
822	return 0;
823}
824
825void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
826{
827	long chg = region_truncate(&inode->i_mapping->private_list, offset);
828	hugetlb_acct_memory(freed - chg);
829}
830