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TOMOYO Linux Cross Reference
Linux/arch/powerpc/mm/slice.c

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  1 /*
  2  * address space "slices" (meta-segments) support
  3  *
  4  * Copyright (C) 2007 Benjamin Herrenschmidt, IBM Corporation.
  5  *
  6  * Based on hugetlb implementation
  7  *
  8  * Copyright (C) 2003 David Gibson, IBM Corporation.
  9  *
 10  * This program is free software; you can redistribute it and/or modify
 11  * it under the terms of the GNU General Public License as published by
 12  * the Free Software Foundation; either version 2 of the License, or
 13  * (at your option) any later version.
 14  *
 15  * This program is distributed in the hope that it will be useful,
 16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 18  * GNU General Public License for more details.
 19  *
 20  * You should have received a copy of the GNU General Public License
 21  * along with this program; if not, write to the Free Software
 22  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 23  */
 24 
 25 #undef DEBUG
 26 
 27 #include <linux/kernel.h>
 28 #include <linux/mm.h>
 29 #include <linux/pagemap.h>
 30 #include <linux/err.h>
 31 #include <linux/spinlock.h>
 32 #include <linux/export.h>
 33 #include <linux/hugetlb.h>
 34 #include <asm/mman.h>
 35 #include <asm/mmu.h>
 36 #include <asm/copro.h>
 37 #include <asm/hugetlb.h>
 38 
 39 /* some sanity checks */
 40 #if (H_PGTABLE_RANGE >> 43) > SLICE_MASK_SIZE
 41 #error H_PGTABLE_RANGE exceeds slice_mask high_slices size
 42 #endif
 43 
 44 static DEFINE_SPINLOCK(slice_convert_lock);
 45 
 46 
 47 #ifdef DEBUG
 48 int _slice_debug = 1;
 49 
 50 static void slice_print_mask(const char *label, struct slice_mask mask)
 51 {
 52         char    *p, buf[16 + 3 + 64 + 1];
 53         int     i;
 54 
 55         if (!_slice_debug)
 56                 return;
 57         p = buf;
 58         for (i = 0; i < SLICE_NUM_LOW; i++)
 59                 *(p++) = (mask.low_slices & (1 << i)) ? '1' : '';
 60         *(p++) = ' ';
 61         *(p++) = '-';
 62         *(p++) = ' ';
 63         for (i = 0; i < SLICE_NUM_HIGH; i++)
 64                 *(p++) = (mask.high_slices & (1ul << i)) ? '1' : '';
 65         *(p++) = 0;
 66 
 67         printk(KERN_DEBUG "%s:%s\n", label, buf);
 68 }
 69 
 70 #define slice_dbg(fmt...) do { if (_slice_debug) pr_debug(fmt); } while(0)
 71 
 72 #else
 73 
 74 static void slice_print_mask(const char *label, struct slice_mask mask) {}
 75 #define slice_dbg(fmt...)
 76 
 77 #endif
 78 
 79 static struct slice_mask slice_range_to_mask(unsigned long start,
 80                                              unsigned long len)
 81 {
 82         unsigned long end = start + len - 1;
 83         struct slice_mask ret = { 0, 0 };
 84 
 85         if (start < SLICE_LOW_TOP) {
 86                 unsigned long mend = min(end, SLICE_LOW_TOP);
 87                 unsigned long mstart = min(start, SLICE_LOW_TOP);
 88 
 89                 ret.low_slices = (1u << (GET_LOW_SLICE_INDEX(mend) + 1))
 90                         - (1u << GET_LOW_SLICE_INDEX(mstart));
 91         }
 92 
 93         if ((start + len) > SLICE_LOW_TOP)
 94                 ret.high_slices = (1ul << (GET_HIGH_SLICE_INDEX(end) + 1))
 95                         - (1ul << GET_HIGH_SLICE_INDEX(start));
 96 
 97         return ret;
 98 }
 99 
100 static int slice_area_is_free(struct mm_struct *mm, unsigned long addr,
101                               unsigned long len)
102 {
103         struct vm_area_struct *vma;
104 
105         if ((mm->task_size - len) < addr)
106                 return 0;
107         vma = find_vma(mm, addr);
108         return (!vma || (addr + len) <= vm_start_gap(vma));
109 }
110 
111 static int slice_low_has_vma(struct mm_struct *mm, unsigned long slice)
112 {
113         return !slice_area_is_free(mm, slice << SLICE_LOW_SHIFT,
114                                    1ul << SLICE_LOW_SHIFT);
115 }
116 
117 static int slice_high_has_vma(struct mm_struct *mm, unsigned long slice)
118 {
119         unsigned long start = slice << SLICE_HIGH_SHIFT;
120         unsigned long end = start + (1ul << SLICE_HIGH_SHIFT);
121 
122         /* Hack, so that each addresses is controlled by exactly one
123          * of the high or low area bitmaps, the first high area starts
124          * at 4GB, not 0 */
125         if (start == 0)
126                 start = SLICE_LOW_TOP;
127 
128         return !slice_area_is_free(mm, start, end - start);
129 }
130 
131 static struct slice_mask slice_mask_for_free(struct mm_struct *mm)
132 {
133         struct slice_mask ret = { 0, 0 };
134         unsigned long i;
135 
136         for (i = 0; i < SLICE_NUM_LOW; i++)
137                 if (!slice_low_has_vma(mm, i))
138                         ret.low_slices |= 1u << i;
139 
140         if (mm->task_size <= SLICE_LOW_TOP)
141                 return ret;
142 
143         for (i = 0; i < SLICE_NUM_HIGH; i++)
144                 if (!slice_high_has_vma(mm, i))
145                         ret.high_slices |= 1ul << i;
146 
147         return ret;
148 }
149 
150 static struct slice_mask slice_mask_for_size(struct mm_struct *mm, int psize)
151 {
152         unsigned char *hpsizes;
153         int index, mask_index;
154         struct slice_mask ret = { 0, 0 };
155         unsigned long i;
156         u64 lpsizes;
157 
158         lpsizes = mm->context.low_slices_psize;
159         for (i = 0; i < SLICE_NUM_LOW; i++)
160                 if (((lpsizes >> (i * 4)) & 0xf) == psize)
161                         ret.low_slices |= 1u << i;
162 
163         hpsizes = mm->context.high_slices_psize;
164         for (i = 0; i < SLICE_NUM_HIGH; i++) {
165                 mask_index = i & 0x1;
166                 index = i >> 1;
167                 if (((hpsizes[index] >> (mask_index * 4)) & 0xf) == psize)
168                         ret.high_slices |= 1ul << i;
169         }
170 
171         return ret;
172 }
173 
174 static int slice_check_fit(struct slice_mask mask, struct slice_mask available)
175 {
176         return (mask.low_slices & available.low_slices) == mask.low_slices &&
177                 (mask.high_slices & available.high_slices) == mask.high_slices;
178 }
179 
180 static void slice_flush_segments(void *parm)
181 {
182         struct mm_struct *mm = parm;
183         unsigned long flags;
184 
185         if (mm != current->active_mm)
186                 return;
187 
188         copy_mm_to_paca(&current->active_mm->context);
189 
190         local_irq_save(flags);
191         slb_flush_and_rebolt();
192         local_irq_restore(flags);
193 }
194 
195 static void slice_convert(struct mm_struct *mm, struct slice_mask mask, int psize)
196 {
197         int index, mask_index;
198         /* Write the new slice psize bits */
199         unsigned char *hpsizes;
200         u64 lpsizes;
201         unsigned long i, flags;
202 
203         slice_dbg("slice_convert(mm=%p, psize=%d)\n", mm, psize);
204         slice_print_mask(" mask", mask);
205 
206         /* We need to use a spinlock here to protect against
207          * concurrent 64k -> 4k demotion ...
208          */
209         spin_lock_irqsave(&slice_convert_lock, flags);
210 
211         lpsizes = mm->context.low_slices_psize;
212         for (i = 0; i < SLICE_NUM_LOW; i++)
213                 if (mask.low_slices & (1u << i))
214                         lpsizes = (lpsizes & ~(0xful << (i * 4))) |
215                                 (((unsigned long)psize) << (i * 4));
216 
217         /* Assign the value back */
218         mm->context.low_slices_psize = lpsizes;
219 
220         hpsizes = mm->context.high_slices_psize;
221         for (i = 0; i < SLICE_NUM_HIGH; i++) {
222                 mask_index = i & 0x1;
223                 index = i >> 1;
224                 if (mask.high_slices & (1ul << i))
225                         hpsizes[index] = (hpsizes[index] &
226                                           ~(0xf << (mask_index * 4))) |
227                                 (((unsigned long)psize) << (mask_index * 4));
228         }
229 
230         slice_dbg(" lsps=%lx, hsps=%lx\n",
231                   mm->context.low_slices_psize,
232                   mm->context.high_slices_psize);
233 
234         spin_unlock_irqrestore(&slice_convert_lock, flags);
235 
236         copro_flush_all_slbs(mm);
237 }
238 
239 /*
240  * Compute which slice addr is part of;
241  * set *boundary_addr to the start or end boundary of that slice
242  * (depending on 'end' parameter);
243  * return boolean indicating if the slice is marked as available in the
244  * 'available' slice_mark.
245  */
246 static bool slice_scan_available(unsigned long addr,
247                                  struct slice_mask available,
248                                  int end,
249                                  unsigned long *boundary_addr)
250 {
251         unsigned long slice;
252         if (addr < SLICE_LOW_TOP) {
253                 slice = GET_LOW_SLICE_INDEX(addr);
254                 *boundary_addr = (slice + end) << SLICE_LOW_SHIFT;
255                 return !!(available.low_slices & (1u << slice));
256         } else {
257                 slice = GET_HIGH_SLICE_INDEX(addr);
258                 *boundary_addr = (slice + end) ?
259                         ((slice + end) << SLICE_HIGH_SHIFT) : SLICE_LOW_TOP;
260                 return !!(available.high_slices & (1ul << slice));
261         }
262 }
263 
264 static unsigned long slice_find_area_bottomup(struct mm_struct *mm,
265                                               unsigned long len,
266                                               struct slice_mask available,
267                                               int psize)
268 {
269         int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
270         unsigned long addr, found, next_end;
271         struct vm_unmapped_area_info info;
272 
273         info.flags = 0;
274         info.length = len;
275         info.align_mask = PAGE_MASK & ((1ul << pshift) - 1);
276         info.align_offset = 0;
277 
278         addr = TASK_UNMAPPED_BASE;
279         while (addr < TASK_SIZE) {
280                 info.low_limit = addr;
281                 if (!slice_scan_available(addr, available, 1, &addr))
282                         continue;
283 
284  next_slice:
285                 /*
286                  * At this point [info.low_limit; addr) covers
287                  * available slices only and ends at a slice boundary.
288                  * Check if we need to reduce the range, or if we can
289                  * extend it to cover the next available slice.
290                  */
291                 if (addr >= TASK_SIZE)
292                         addr = TASK_SIZE;
293                 else if (slice_scan_available(addr, available, 1, &next_end)) {
294                         addr = next_end;
295                         goto next_slice;
296                 }
297                 info.high_limit = addr;
298 
299                 found = vm_unmapped_area(&info);
300                 if (!(found & ~PAGE_MASK))
301                         return found;
302         }
303 
304         return -ENOMEM;
305 }
306 
307 static unsigned long slice_find_area_topdown(struct mm_struct *mm,
308                                              unsigned long len,
309                                              struct slice_mask available,
310                                              int psize)
311 {
312         int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
313         unsigned long addr, found, prev;
314         struct vm_unmapped_area_info info;
315 
316         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
317         info.length = len;
318         info.align_mask = PAGE_MASK & ((1ul << pshift) - 1);
319         info.align_offset = 0;
320 
321         addr = mm->mmap_base;
322         while (addr > PAGE_SIZE) {
323                 info.high_limit = addr;
324                 if (!slice_scan_available(addr - 1, available, 0, &addr))
325                         continue;
326 
327  prev_slice:
328                 /*
329                  * At this point [addr; info.high_limit) covers
330                  * available slices only and starts at a slice boundary.
331                  * Check if we need to reduce the range, or if we can
332                  * extend it to cover the previous available slice.
333                  */
334                 if (addr < PAGE_SIZE)
335                         addr = PAGE_SIZE;
336                 else if (slice_scan_available(addr - 1, available, 0, &prev)) {
337                         addr = prev;
338                         goto prev_slice;
339                 }
340                 info.low_limit = addr;
341 
342                 found = vm_unmapped_area(&info);
343                 if (!(found & ~PAGE_MASK))
344                         return found;
345         }
346 
347         /*
348          * A failed mmap() very likely causes application failure,
349          * so fall back to the bottom-up function here. This scenario
350          * can happen with large stack limits and large mmap()
351          * allocations.
352          */
353         return slice_find_area_bottomup(mm, len, available, psize);
354 }
355 
356 
357 static unsigned long slice_find_area(struct mm_struct *mm, unsigned long len,
358                                      struct slice_mask mask, int psize,
359                                      int topdown)
360 {
361         if (topdown)
362                 return slice_find_area_topdown(mm, len, mask, psize);
363         else
364                 return slice_find_area_bottomup(mm, len, mask, psize);
365 }
366 
367 #define or_mask(dst, src)       do {                    \
368         (dst).low_slices |= (src).low_slices;           \
369         (dst).high_slices |= (src).high_slices;         \
370 } while (0)
371 
372 #define andnot_mask(dst, src)   do {                    \
373         (dst).low_slices &= ~(src).low_slices;          \
374         (dst).high_slices &= ~(src).high_slices;        \
375 } while (0)
376 
377 #ifdef CONFIG_PPC_64K_PAGES
378 #define MMU_PAGE_BASE   MMU_PAGE_64K
379 #else
380 #define MMU_PAGE_BASE   MMU_PAGE_4K
381 #endif
382 
383 unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
384                                       unsigned long flags, unsigned int psize,
385                                       int topdown)
386 {
387         struct slice_mask mask = {0, 0};
388         struct slice_mask good_mask;
389         struct slice_mask potential_mask = {0,0} /* silence stupid warning */;
390         struct slice_mask compat_mask = {0, 0};
391         int fixed = (flags & MAP_FIXED);
392         int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
393         struct mm_struct *mm = current->mm;
394         unsigned long newaddr;
395 
396         /* Sanity checks */
397         BUG_ON(mm->task_size == 0);
398         VM_BUG_ON(radix_enabled());
399 
400         slice_dbg("slice_get_unmapped_area(mm=%p, psize=%d...\n", mm, psize);
401         slice_dbg(" addr=%lx, len=%lx, flags=%lx, topdown=%d\n",
402                   addr, len, flags, topdown);
403 
404         if (len > mm->task_size)
405                 return -ENOMEM;
406         if (len & ((1ul << pshift) - 1))
407                 return -EINVAL;
408         if (fixed && (addr & ((1ul << pshift) - 1)))
409                 return -EINVAL;
410         if (fixed && addr > (mm->task_size - len))
411                 return -ENOMEM;
412 
413         /* If hint, make sure it matches our alignment restrictions */
414         if (!fixed && addr) {
415                 addr = _ALIGN_UP(addr, 1ul << pshift);
416                 slice_dbg(" aligned addr=%lx\n", addr);
417                 /* Ignore hint if it's too large or overlaps a VMA */
418                 if (addr > mm->task_size - len ||
419                     !slice_area_is_free(mm, addr, len))
420                         addr = 0;
421         }
422 
423         /* First make up a "good" mask of slices that have the right size
424          * already
425          */
426         good_mask = slice_mask_for_size(mm, psize);
427         slice_print_mask(" good_mask", good_mask);
428 
429         /*
430          * Here "good" means slices that are already the right page size,
431          * "compat" means slices that have a compatible page size (i.e.
432          * 4k in a 64k pagesize kernel), and "free" means slices without
433          * any VMAs.
434          *
435          * If MAP_FIXED:
436          *      check if fits in good | compat => OK
437          *      check if fits in good | compat | free => convert free
438          *      else bad
439          * If have hint:
440          *      check if hint fits in good => OK
441          *      check if hint fits in good | free => convert free
442          * Otherwise:
443          *      search in good, found => OK
444          *      search in good | free, found => convert free
445          *      search in good | compat | free, found => convert free.
446          */
447 
448 #ifdef CONFIG_PPC_64K_PAGES
449         /* If we support combo pages, we can allow 64k pages in 4k slices */
450         if (psize == MMU_PAGE_64K) {
451                 compat_mask = slice_mask_for_size(mm, MMU_PAGE_4K);
452                 if (fixed)
453                         or_mask(good_mask, compat_mask);
454         }
455 #endif
456 
457         /* First check hint if it's valid or if we have MAP_FIXED */
458         if (addr != 0 || fixed) {
459                 /* Build a mask for the requested range */
460                 mask = slice_range_to_mask(addr, len);
461                 slice_print_mask(" mask", mask);
462 
463                 /* Check if we fit in the good mask. If we do, we just return,
464                  * nothing else to do
465                  */
466                 if (slice_check_fit(mask, good_mask)) {
467                         slice_dbg(" fits good !\n");
468                         return addr;
469                 }
470         } else {
471                 /* Now let's see if we can find something in the existing
472                  * slices for that size
473                  */
474                 newaddr = slice_find_area(mm, len, good_mask, psize, topdown);
475                 if (newaddr != -ENOMEM) {
476                         /* Found within the good mask, we don't have to setup,
477                          * we thus return directly
478                          */
479                         slice_dbg(" found area at 0x%lx\n", newaddr);
480                         return newaddr;
481                 }
482         }
483 
484         /* We don't fit in the good mask, check what other slices are
485          * empty and thus can be converted
486          */
487         potential_mask = slice_mask_for_free(mm);
488         or_mask(potential_mask, good_mask);
489         slice_print_mask(" potential", potential_mask);
490 
491         if ((addr != 0 || fixed) && slice_check_fit(mask, potential_mask)) {
492                 slice_dbg(" fits potential !\n");
493                 goto convert;
494         }
495 
496         /* If we have MAP_FIXED and failed the above steps, then error out */
497         if (fixed)
498                 return -EBUSY;
499 
500         slice_dbg(" search...\n");
501 
502         /* If we had a hint that didn't work out, see if we can fit
503          * anywhere in the good area.
504          */
505         if (addr) {
506                 addr = slice_find_area(mm, len, good_mask, psize, topdown);
507                 if (addr != -ENOMEM) {
508                         slice_dbg(" found area at 0x%lx\n", addr);
509                         return addr;
510                 }
511         }
512 
513         /* Now let's see if we can find something in the existing slices
514          * for that size plus free slices
515          */
516         addr = slice_find_area(mm, len, potential_mask, psize, topdown);
517 
518 #ifdef CONFIG_PPC_64K_PAGES
519         if (addr == -ENOMEM && psize == MMU_PAGE_64K) {
520                 /* retry the search with 4k-page slices included */
521                 or_mask(potential_mask, compat_mask);
522                 addr = slice_find_area(mm, len, potential_mask, psize,
523                                        topdown);
524         }
525 #endif
526 
527         if (addr == -ENOMEM)
528                 return -ENOMEM;
529 
530         mask = slice_range_to_mask(addr, len);
531         slice_dbg(" found potential area at 0x%lx\n", addr);
532         slice_print_mask(" mask", mask);
533 
534  convert:
535         andnot_mask(mask, good_mask);
536         andnot_mask(mask, compat_mask);
537         if (mask.low_slices || mask.high_slices) {
538                 slice_convert(mm, mask, psize);
539                 if (psize > MMU_PAGE_BASE)
540                         on_each_cpu(slice_flush_segments, mm, 1);
541         }
542         return addr;
543 
544 }
545 EXPORT_SYMBOL_GPL(slice_get_unmapped_area);
546 
547 unsigned long arch_get_unmapped_area(struct file *filp,
548                                      unsigned long addr,
549                                      unsigned long len,
550                                      unsigned long pgoff,
551                                      unsigned long flags)
552 {
553         return slice_get_unmapped_area(addr, len, flags,
554                                        current->mm->context.user_psize, 0);
555 }
556 
557 unsigned long arch_get_unmapped_area_topdown(struct file *filp,
558                                              const unsigned long addr0,
559                                              const unsigned long len,
560                                              const unsigned long pgoff,
561                                              const unsigned long flags)
562 {
563         return slice_get_unmapped_area(addr0, len, flags,
564                                        current->mm->context.user_psize, 1);
565 }
566 
567 unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)
568 {
569         unsigned char *hpsizes;
570         int index, mask_index;
571 
572         /*
573          * Radix doesn't use slice, but can get enabled along with MMU_SLICE
574          */
575         if (radix_enabled()) {
576 #ifdef CONFIG_PPC_64K_PAGES
577                 return MMU_PAGE_64K;
578 #else
579                 return MMU_PAGE_4K;
580 #endif
581         }
582         if (addr < SLICE_LOW_TOP) {
583                 u64 lpsizes;
584                 lpsizes = mm->context.low_slices_psize;
585                 index = GET_LOW_SLICE_INDEX(addr);
586                 return (lpsizes >> (index * 4)) & 0xf;
587         }
588         hpsizes = mm->context.high_slices_psize;
589         index = GET_HIGH_SLICE_INDEX(addr);
590         mask_index = index & 0x1;
591         return (hpsizes[index >> 1] >> (mask_index * 4)) & 0xf;
592 }
593 EXPORT_SYMBOL_GPL(get_slice_psize);
594 
595 /*
596  * This is called by hash_page when it needs to do a lazy conversion of
597  * an address space from real 64K pages to combo 4K pages (typically
598  * when hitting a non cacheable mapping on a processor or hypervisor
599  * that won't allow them for 64K pages).
600  *
601  * This is also called in init_new_context() to change back the user
602  * psize from whatever the parent context had it set to
603  * N.B. This may be called before mm->context.id has been set.
604  *
605  * This function will only change the content of the {low,high)_slice_psize
606  * masks, it will not flush SLBs as this shall be handled lazily by the
607  * caller.
608  */
609 void slice_set_user_psize(struct mm_struct *mm, unsigned int psize)
610 {
611         int index, mask_index;
612         unsigned char *hpsizes;
613         unsigned long flags, lpsizes;
614         unsigned int old_psize;
615         int i;
616 
617         slice_dbg("slice_set_user_psize(mm=%p, psize=%d)\n", mm, psize);
618 
619         VM_BUG_ON(radix_enabled());
620         spin_lock_irqsave(&slice_convert_lock, flags);
621 
622         old_psize = mm->context.user_psize;
623         slice_dbg(" old_psize=%d\n", old_psize);
624         if (old_psize == psize)
625                 goto bail;
626 
627         mm->context.user_psize = psize;
628         wmb();
629 
630         lpsizes = mm->context.low_slices_psize;
631         for (i = 0; i < SLICE_NUM_LOW; i++)
632                 if (((lpsizes >> (i * 4)) & 0xf) == old_psize)
633                         lpsizes = (lpsizes & ~(0xful << (i * 4))) |
634                                 (((unsigned long)psize) << (i * 4));
635         /* Assign the value back */
636         mm->context.low_slices_psize = lpsizes;
637 
638         hpsizes = mm->context.high_slices_psize;
639         for (i = 0; i < SLICE_NUM_HIGH; i++) {
640                 mask_index = i & 0x1;
641                 index = i >> 1;
642                 if (((hpsizes[index] >> (mask_index * 4)) & 0xf) == old_psize)
643                         hpsizes[index] = (hpsizes[index] &
644                                           ~(0xf << (mask_index * 4))) |
645                                 (((unsigned long)psize) << (mask_index * 4));
646         }
647 
648 
649 
650 
651         slice_dbg(" lsps=%lx, hsps=%lx\n",
652                   mm->context.low_slices_psize,
653                   mm->context.high_slices_psize);
654 
655  bail:
656         spin_unlock_irqrestore(&slice_convert_lock, flags);
657 }
658 
659 void slice_set_range_psize(struct mm_struct *mm, unsigned long start,
660                            unsigned long len, unsigned int psize)
661 {
662         struct slice_mask mask = slice_range_to_mask(start, len);
663 
664         VM_BUG_ON(radix_enabled());
665         slice_convert(mm, mask, psize);
666 }
667 
668 #ifdef CONFIG_HUGETLB_PAGE
669 /*
670  * is_hugepage_only_range() is used by generic code to verify whether
671  * a normal mmap mapping (non hugetlbfs) is valid on a given area.
672  *
673  * until the generic code provides a more generic hook and/or starts
674  * calling arch get_unmapped_area for MAP_FIXED (which our implementation
675  * here knows how to deal with), we hijack it to keep standard mappings
676  * away from us.
677  *
678  * because of that generic code limitation, MAP_FIXED mapping cannot
679  * "convert" back a slice with no VMAs to the standard page size, only
680  * get_unmapped_area() can. It would be possible to fix it here but I
681  * prefer working on fixing the generic code instead.
682  *
683  * WARNING: This will not work if hugetlbfs isn't enabled since the
684  * generic code will redefine that function as 0 in that. This is ok
685  * for now as we only use slices with hugetlbfs enabled. This should
686  * be fixed as the generic code gets fixed.
687  */
688 int is_hugepage_only_range(struct mm_struct *mm, unsigned long addr,
689                            unsigned long len)
690 {
691         struct slice_mask mask, available;
692         unsigned int psize = mm->context.user_psize;
693 
694         if (radix_enabled())
695                 return 0;
696 
697         mask = slice_range_to_mask(addr, len);
698         available = slice_mask_for_size(mm, psize);
699 #ifdef CONFIG_PPC_64K_PAGES
700         /* We need to account for 4k slices too */
701         if (psize == MMU_PAGE_64K) {
702                 struct slice_mask compat_mask;
703                 compat_mask = slice_mask_for_size(mm, MMU_PAGE_4K);
704                 or_mask(available, compat_mask);
705         }
706 #endif
707 
708 #if 0 /* too verbose */
709         slice_dbg("is_hugepage_only_range(mm=%p, addr=%lx, len=%lx)\n",
710                  mm, addr, len);
711         slice_print_mask(" mask", mask);
712         slice_print_mask(" available", available);
713 #endif
714         return !slice_check_fit(mask, available);
715 }
716 #endif
717 

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