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Linux/arch/x86/mm/hugetlbpage.c

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  1 /*
  2  * IA-32 Huge TLB Page Support for Kernel.
  3  *
  4  * Copyright (C) 2002, Rohit Seth <rohit.seth@intel.com>
  5  */
  6 
  7 #include <linux/init.h>
  8 #include <linux/fs.h>
  9 #include <linux/mm.h>
 10 #include <linux/hugetlb.h>
 11 #include <linux/pagemap.h>
 12 #include <linux/err.h>
 13 #include <linux/sysctl.h>
 14 #include <asm/mman.h>
 15 #include <asm/tlb.h>
 16 #include <asm/tlbflush.h>
 17 #include <asm/pgalloc.h>
 18 
 19 static unsigned long page_table_shareable(struct vm_area_struct *svma,
 20                                 struct vm_area_struct *vma,
 21                                 unsigned long addr, pgoff_t idx)
 22 {
 23         unsigned long saddr = ((idx - svma->vm_pgoff) << PAGE_SHIFT) +
 24                                 svma->vm_start;
 25         unsigned long sbase = saddr & PUD_MASK;
 26         unsigned long s_end = sbase + PUD_SIZE;
 27 
 28         /* Allow segments to share if only one is marked locked */
 29         unsigned long vm_flags = vma->vm_flags & ~VM_LOCKED;
 30         unsigned long svm_flags = svma->vm_flags & ~VM_LOCKED;
 31 
 32         /*
 33          * match the virtual addresses, permission and the alignment of the
 34          * page table page.
 35          */
 36         if (pmd_index(addr) != pmd_index(saddr) ||
 37             vm_flags != svm_flags ||
 38             sbase < svma->vm_start || svma->vm_end < s_end)
 39                 return 0;
 40 
 41         return saddr;
 42 }
 43 
 44 static int vma_shareable(struct vm_area_struct *vma, unsigned long addr)
 45 {
 46         unsigned long base = addr & PUD_MASK;
 47         unsigned long end = base + PUD_SIZE;
 48 
 49         /*
 50          * check on proper vm_flags and page table alignment
 51          */
 52         if (vma->vm_flags & VM_MAYSHARE &&
 53             vma->vm_start <= base && end <= vma->vm_end)
 54                 return 1;
 55         return 0;
 56 }
 57 
 58 /*
 59  * Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
 60  * and returns the corresponding pte. While this is not necessary for the
 61  * !shared pmd case because we can allocate the pmd later as well, it makes the
 62  * code much cleaner. pmd allocation is essential for the shared case because
 63  * pud has to be populated inside the same i_mmap_mutex section - otherwise
 64  * racing tasks could either miss the sharing (see huge_pte_offset) or select a
 65  * bad pmd for sharing.
 66  */
 67 static pte_t *
 68 huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
 69 {
 70         struct vm_area_struct *vma = find_vma(mm, addr);
 71         struct address_space *mapping = vma->vm_file->f_mapping;
 72         pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
 73                         vma->vm_pgoff;
 74         struct prio_tree_iter iter;
 75         struct vm_area_struct *svma;
 76         unsigned long saddr;
 77         pte_t *spte = NULL;
 78         pte_t *pte;
 79 
 80         if (!vma_shareable(vma, addr))
 81                 return (pte_t *)pmd_alloc(mm, pud, addr);
 82 
 83         mutex_lock(&mapping->i_mmap_mutex);
 84         vma_prio_tree_foreach(svma, &iter, &mapping->i_mmap, idx, idx) {
 85                 if (svma == vma)
 86                         continue;
 87 
 88                 saddr = page_table_shareable(svma, vma, addr, idx);
 89                 if (saddr) {
 90                         spte = huge_pte_offset(svma->vm_mm, saddr);
 91                         if (spte) {
 92                                 get_page(virt_to_page(spte));
 93                                 break;
 94                         }
 95                 }
 96         }
 97 
 98         if (!spte)
 99                 goto out;
100 
101         spin_lock(&mm->page_table_lock);
102         if (pud_none(*pud))
103                 pud_populate(mm, pud, (pmd_t *)((unsigned long)spte & PAGE_MASK));
104         else
105                 put_page(virt_to_page(spte));
106         spin_unlock(&mm->page_table_lock);
107 out:
108         pte = (pte_t *)pmd_alloc(mm, pud, addr);
109         mutex_unlock(&mapping->i_mmap_mutex);
110         return pte;
111 }
112 
113 /*
114  * unmap huge page backed by shared pte.
115  *
116  * Hugetlb pte page is ref counted at the time of mapping.  If pte is shared
117  * indicated by page_count > 1, unmap is achieved by clearing pud and
118  * decrementing the ref count. If count == 1, the pte page is not shared.
119  *
120  * called with vma->vm_mm->page_table_lock held.
121  *
122  * returns: 1 successfully unmapped a shared pte page
123  *          0 the underlying pte page is not shared, or it is the last user
124  */
125 int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
126 {
127         pgd_t *pgd = pgd_offset(mm, *addr);
128         pud_t *pud = pud_offset(pgd, *addr);
129 
130         BUG_ON(page_count(virt_to_page(ptep)) == 0);
131         if (page_count(virt_to_page(ptep)) == 1)
132                 return 0;
133 
134         pud_clear(pud);
135         put_page(virt_to_page(ptep));
136         *addr = ALIGN(*addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE;
137         return 1;
138 }
139 
140 pte_t *huge_pte_alloc(struct mm_struct *mm,
141                         unsigned long addr, unsigned long sz)
142 {
143         pgd_t *pgd;
144         pud_t *pud;
145         pte_t *pte = NULL;
146 
147         pgd = pgd_offset(mm, addr);
148         pud = pud_alloc(mm, pgd, addr);
149         if (pud) {
150                 if (sz == PUD_SIZE) {
151                         pte = (pte_t *)pud;
152                 } else {
153                         BUG_ON(sz != PMD_SIZE);
154                         if (pud_none(*pud))
155                                 pte = huge_pmd_share(mm, addr, pud);
156                         else
157                                 pte = (pte_t *)pmd_alloc(mm, pud, addr);
158                 }
159         }
160         BUG_ON(pte && !pte_none(*pte) && !pte_huge(*pte));
161 
162         return pte;
163 }
164 
165 pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
166 {
167         pgd_t *pgd;
168         pud_t *pud;
169         pmd_t *pmd = NULL;
170 
171         pgd = pgd_offset(mm, addr);
172         if (pgd_present(*pgd)) {
173                 pud = pud_offset(pgd, addr);
174                 if (pud_present(*pud)) {
175                         if (pud_large(*pud))
176                                 return (pte_t *)pud;
177                         pmd = pmd_offset(pud, addr);
178                 }
179         }
180         return (pte_t *) pmd;
181 }
182 
183 #if 0   /* This is just for testing */
184 struct page *
185 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
186 {
187         unsigned long start = address;
188         int length = 1;
189         int nr;
190         struct page *page;
191         struct vm_area_struct *vma;
192 
193         vma = find_vma(mm, addr);
194         if (!vma || !is_vm_hugetlb_page(vma))
195                 return ERR_PTR(-EINVAL);
196 
197         pte = huge_pte_offset(mm, address);
198 
199         /* hugetlb should be locked, and hence, prefaulted */
200         WARN_ON(!pte || pte_none(*pte));
201 
202         page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
203 
204         WARN_ON(!PageHead(page));
205 
206         return page;
207 }
208 
209 int pmd_huge(pmd_t pmd)
210 {
211         return 0;
212 }
213 
214 int pud_huge(pud_t pud)
215 {
216         return 0;
217 }
218 
219 struct page *
220 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
221                 pmd_t *pmd, int write)
222 {
223         return NULL;
224 }
225 
226 #else
227 
228 struct page *
229 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
230 {
231         return ERR_PTR(-EINVAL);
232 }
233 
234 int pmd_huge(pmd_t pmd)
235 {
236         return !!(pmd_val(pmd) & _PAGE_PSE);
237 }
238 
239 int pud_huge(pud_t pud)
240 {
241         return !!(pud_val(pud) & _PAGE_PSE);
242 }
243 
244 struct page *
245 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
246                 pmd_t *pmd, int write)
247 {
248         struct page *page;
249 
250         page = pte_page(*(pte_t *)pmd);
251         if (page)
252                 page += ((address & ~PMD_MASK) >> PAGE_SHIFT);
253         return page;
254 }
255 
256 struct page *
257 follow_huge_pud(struct mm_struct *mm, unsigned long address,
258                 pud_t *pud, int write)
259 {
260         struct page *page;
261 
262         page = pte_page(*(pte_t *)pud);
263         if (page)
264                 page += ((address & ~PUD_MASK) >> PAGE_SHIFT);
265         return page;
266 }
267 
268 #endif
269 
270 /* x86_64 also uses this file */
271 
272 #ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
273 static unsigned long hugetlb_get_unmapped_area_bottomup(struct file *file,
274                 unsigned long addr, unsigned long len,
275                 unsigned long pgoff, unsigned long flags)
276 {
277         struct hstate *h = hstate_file(file);
278         struct mm_struct *mm = current->mm;
279         struct vm_area_struct *vma;
280         unsigned long start_addr;
281 
282         if (len > mm->cached_hole_size) {
283                 start_addr = mm->free_area_cache;
284         } else {
285                 start_addr = TASK_UNMAPPED_BASE;
286                 mm->cached_hole_size = 0;
287         }
288 
289 full_search:
290         addr = ALIGN(start_addr, huge_page_size(h));
291 
292         for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
293                 /* At this point:  (!vma || addr < vma->vm_end). */
294                 if (TASK_SIZE - len < addr) {
295                         /*
296                          * Start a new search - just in case we missed
297                          * some holes.
298                          */
299                         if (start_addr != TASK_UNMAPPED_BASE) {
300                                 start_addr = TASK_UNMAPPED_BASE;
301                                 mm->cached_hole_size = 0;
302                                 goto full_search;
303                         }
304                         return -ENOMEM;
305                 }
306                 if (!vma || addr + len <= vma->vm_start) {
307                         mm->free_area_cache = addr + len;
308                         return addr;
309                 }
310                 if (addr + mm->cached_hole_size < vma->vm_start)
311                         mm->cached_hole_size = vma->vm_start - addr;
312                 addr = ALIGN(vma->vm_end, huge_page_size(h));
313         }
314 }
315 
316 static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
317                 unsigned long addr0, unsigned long len,
318                 unsigned long pgoff, unsigned long flags)
319 {
320         struct hstate *h = hstate_file(file);
321         struct mm_struct *mm = current->mm;
322         struct vm_area_struct *vma;
323         unsigned long base = mm->mmap_base;
324         unsigned long addr = addr0;
325         unsigned long largest_hole = mm->cached_hole_size;
326         unsigned long start_addr;
327 
328         /* don't allow allocations above current base */
329         if (mm->free_area_cache > base)
330                 mm->free_area_cache = base;
331 
332         if (len <= largest_hole) {
333                 largest_hole = 0;
334                 mm->free_area_cache  = base;
335         }
336 try_again:
337         start_addr = mm->free_area_cache;
338 
339         /* make sure it can fit in the remaining address space */
340         if (mm->free_area_cache < len)
341                 goto fail;
342 
343         /* either no address requested or can't fit in requested address hole */
344         addr = (mm->free_area_cache - len) & huge_page_mask(h);
345         do {
346                 /*
347                  * Lookup failure means no vma is above this address,
348                  * i.e. return with success:
349                  */
350                 vma = find_vma(mm, addr);
351                 if (!vma)
352                         return addr;
353 
354                 if (addr + len <= vma->vm_start) {
355                         /* remember the address as a hint for next time */
356                         mm->cached_hole_size = largest_hole;
357                         return (mm->free_area_cache = addr);
358                 } else if (mm->free_area_cache == vma->vm_end) {
359                         /* pull free_area_cache down to the first hole */
360                         mm->free_area_cache = vma->vm_start;
361                         mm->cached_hole_size = largest_hole;
362                 }
363 
364                 /* remember the largest hole we saw so far */
365                 if (addr + largest_hole < vma->vm_start)
366                         largest_hole = vma->vm_start - addr;
367 
368                 /* try just below the current vma->vm_start */
369                 addr = (vma->vm_start - len) & huge_page_mask(h);
370         } while (len <= vma->vm_start);
371 
372 fail:
373         /*
374          * if hint left us with no space for the requested
375          * mapping then try again:
376          */
377         if (start_addr != base) {
378                 mm->free_area_cache = base;
379                 largest_hole = 0;
380                 goto try_again;
381         }
382         /*
383          * A failed mmap() very likely causes application failure,
384          * so fall back to the bottom-up function here. This scenario
385          * can happen with large stack limits and large mmap()
386          * allocations.
387          */
388         mm->free_area_cache = TASK_UNMAPPED_BASE;
389         mm->cached_hole_size = ~0UL;
390         addr = hugetlb_get_unmapped_area_bottomup(file, addr0,
391                         len, pgoff, flags);
392 
393         /*
394          * Restore the topdown base:
395          */
396         mm->free_area_cache = base;
397         mm->cached_hole_size = ~0UL;
398 
399         return addr;
400 }
401 
402 unsigned long
403 hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
404                 unsigned long len, unsigned long pgoff, unsigned long flags)
405 {
406         struct hstate *h = hstate_file(file);
407         struct mm_struct *mm = current->mm;
408         struct vm_area_struct *vma;
409 
410         if (len & ~huge_page_mask(h))
411                 return -EINVAL;
412         if (len > TASK_SIZE)
413                 return -ENOMEM;
414 
415         if (flags & MAP_FIXED) {
416                 if (prepare_hugepage_range(file, addr, len))
417                         return -EINVAL;
418                 return addr;
419         }
420 
421         if (addr) {
422                 addr = ALIGN(addr, huge_page_size(h));
423                 vma = find_vma(mm, addr);
424                 if (TASK_SIZE - len >= addr &&
425                     (!vma || addr + len <= vma->vm_start))
426                         return addr;
427         }
428         if (mm->get_unmapped_area == arch_get_unmapped_area)
429                 return hugetlb_get_unmapped_area_bottomup(file, addr, len,
430                                 pgoff, flags);
431         else
432                 return hugetlb_get_unmapped_area_topdown(file, addr, len,
433                                 pgoff, flags);
434 }
435 
436 #endif /*HAVE_ARCH_HUGETLB_UNMAPPED_AREA*/
437 
438 #ifdef CONFIG_X86_64
439 static __init int setup_hugepagesz(char *opt)
440 {
441         unsigned long ps = memparse(opt, &opt);
442         if (ps == PMD_SIZE) {
443                 hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
444         } else if (ps == PUD_SIZE && cpu_has_gbpages) {
445                 hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
446         } else {
447                 printk(KERN_ERR "hugepagesz: Unsupported page size %lu M\n",
448                         ps >> 20);
449                 return 0;
450         }
451         return 1;
452 }
453 __setup("hugepagesz=", setup_hugepagesz);
454 #endif
455 

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