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TOMOYO Linux Cross Reference
Linux/mm/sparse.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * sparse memory mappings.
  4  */
  5 #include <linux/mm.h>
  6 #include <linux/slab.h>
  7 #include <linux/mmzone.h>
  8 #include <linux/memblock.h>
  9 #include <linux/compiler.h>
 10 #include <linux/highmem.h>
 11 #include <linux/export.h>
 12 #include <linux/spinlock.h>
 13 #include <linux/vmalloc.h>
 14 #include <linux/swap.h>
 15 #include <linux/swapops.h>
 16 #include <linux/bootmem_info.h>
 17 
 18 #include "internal.h"
 19 #include <asm/dma.h>
 20 
 21 /*
 22  * Permanent SPARSEMEM data:
 23  *
 24  * 1) mem_section       - memory sections, mem_map's for valid memory
 25  */
 26 #ifdef CONFIG_SPARSEMEM_EXTREME
 27 struct mem_section **mem_section;
 28 #else
 29 struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]
 30         ____cacheline_internodealigned_in_smp;
 31 #endif
 32 EXPORT_SYMBOL(mem_section);
 33 
 34 #ifdef NODE_NOT_IN_PAGE_FLAGS
 35 /*
 36  * If we did not store the node number in the page then we have to
 37  * do a lookup in the section_to_node_table in order to find which
 38  * node the page belongs to.
 39  */
 40 #if MAX_NUMNODES <= 256
 41 static u8 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned;
 42 #else
 43 static u16 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned;
 44 #endif
 45 
 46 int page_to_nid(const struct page *page)
 47 {
 48         return section_to_node_table[page_to_section(page)];
 49 }
 50 EXPORT_SYMBOL(page_to_nid);
 51 
 52 static void set_section_nid(unsigned long section_nr, int nid)
 53 {
 54         section_to_node_table[section_nr] = nid;
 55 }
 56 #else /* !NODE_NOT_IN_PAGE_FLAGS */
 57 static inline void set_section_nid(unsigned long section_nr, int nid)
 58 {
 59 }
 60 #endif
 61 
 62 #ifdef CONFIG_SPARSEMEM_EXTREME
 63 static noinline struct mem_section __ref *sparse_index_alloc(int nid)
 64 {
 65         struct mem_section *section = NULL;
 66         unsigned long array_size = SECTIONS_PER_ROOT *
 67                                    sizeof(struct mem_section);
 68 
 69         if (slab_is_available()) {
 70                 section = kzalloc_node(array_size, GFP_KERNEL, nid);
 71         } else {
 72                 section = memblock_alloc_node(array_size, SMP_CACHE_BYTES,
 73                                               nid);
 74                 if (!section)
 75                         panic("%s: Failed to allocate %lu bytes nid=%d\n",
 76                               __func__, array_size, nid);
 77         }
 78 
 79         return section;
 80 }
 81 
 82 static int __meminit sparse_index_init(unsigned long section_nr, int nid)
 83 {
 84         unsigned long root = SECTION_NR_TO_ROOT(section_nr);
 85         struct mem_section *section;
 86 
 87         /*
 88          * An existing section is possible in the sub-section hotplug
 89          * case. First hot-add instantiates, follow-on hot-add reuses
 90          * the existing section.
 91          *
 92          * The mem_hotplug_lock resolves the apparent race below.
 93          */
 94         if (mem_section[root])
 95                 return 0;
 96 
 97         section = sparse_index_alloc(nid);
 98         if (!section)
 99                 return -ENOMEM;
100 
101         mem_section[root] = section;
102 
103         return 0;
104 }
105 #else /* !SPARSEMEM_EXTREME */
106 static inline int sparse_index_init(unsigned long section_nr, int nid)
107 {
108         return 0;
109 }
110 #endif
111 
112 /*
113  * During early boot, before section_mem_map is used for an actual
114  * mem_map, we use section_mem_map to store the section's NUMA
115  * node.  This keeps us from having to use another data structure.  The
116  * node information is cleared just before we store the real mem_map.
117  */
118 static inline unsigned long sparse_encode_early_nid(int nid)
119 {
120         return ((unsigned long)nid << SECTION_NID_SHIFT);
121 }
122 
123 static inline int sparse_early_nid(struct mem_section *section)
124 {
125         return (section->section_mem_map >> SECTION_NID_SHIFT);
126 }
127 
128 /* Validate the physical addressing limitations of the model */
129 static void __meminit mminit_validate_memmodel_limits(unsigned long *start_pfn,
130                                                 unsigned long *end_pfn)
131 {
132         unsigned long max_sparsemem_pfn = 1UL << (MAX_PHYSMEM_BITS-PAGE_SHIFT);
133 
134         /*
135          * Sanity checks - do not allow an architecture to pass
136          * in larger pfns than the maximum scope of sparsemem:
137          */
138         if (*start_pfn > max_sparsemem_pfn) {
139                 mminit_dprintk(MMINIT_WARNING, "pfnvalidation",
140                         "Start of range %lu -> %lu exceeds SPARSEMEM max %lu\n",
141                         *start_pfn, *end_pfn, max_sparsemem_pfn);
142                 WARN_ON_ONCE(1);
143                 *start_pfn = max_sparsemem_pfn;
144                 *end_pfn = max_sparsemem_pfn;
145         } else if (*end_pfn > max_sparsemem_pfn) {
146                 mminit_dprintk(MMINIT_WARNING, "pfnvalidation",
147                         "End of range %lu -> %lu exceeds SPARSEMEM max %lu\n",
148                         *start_pfn, *end_pfn, max_sparsemem_pfn);
149                 WARN_ON_ONCE(1);
150                 *end_pfn = max_sparsemem_pfn;
151         }
152 }
153 
154 /*
155  * There are a number of times that we loop over NR_MEM_SECTIONS,
156  * looking for section_present() on each.  But, when we have very
157  * large physical address spaces, NR_MEM_SECTIONS can also be
158  * very large which makes the loops quite long.
159  *
160  * Keeping track of this gives us an easy way to break out of
161  * those loops early.
162  */
163 unsigned long __highest_present_section_nr;
164 static void __section_mark_present(struct mem_section *ms,
165                 unsigned long section_nr)
166 {
167         if (section_nr > __highest_present_section_nr)
168                 __highest_present_section_nr = section_nr;
169 
170         ms->section_mem_map |= SECTION_MARKED_PRESENT;
171 }
172 
173 #define for_each_present_section_nr(start, section_nr)          \
174         for (section_nr = next_present_section_nr(start-1);     \
175              ((section_nr != -1) &&                             \
176               (section_nr <= __highest_present_section_nr));    \
177              section_nr = next_present_section_nr(section_nr))
178 
179 static inline unsigned long first_present_section_nr(void)
180 {
181         return next_present_section_nr(-1);
182 }
183 
184 #ifdef CONFIG_SPARSEMEM_VMEMMAP
185 static void subsection_mask_set(unsigned long *map, unsigned long pfn,
186                 unsigned long nr_pages)
187 {
188         int idx = subsection_map_index(pfn);
189         int end = subsection_map_index(pfn + nr_pages - 1);
190 
191         bitmap_set(map, idx, end - idx + 1);
192 }
193 
194 void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
195 {
196         int end_sec = pfn_to_section_nr(pfn + nr_pages - 1);
197         unsigned long nr, start_sec = pfn_to_section_nr(pfn);
198 
199         if (!nr_pages)
200                 return;
201 
202         for (nr = start_sec; nr <= end_sec; nr++) {
203                 struct mem_section *ms;
204                 unsigned long pfns;
205 
206                 pfns = min(nr_pages, PAGES_PER_SECTION
207                                 - (pfn & ~PAGE_SECTION_MASK));
208                 ms = __nr_to_section(nr);
209                 subsection_mask_set(ms->usage->subsection_map, pfn, pfns);
210 
211                 pr_debug("%s: sec: %lu pfns: %lu set(%d, %d)\n", __func__, nr,
212                                 pfns, subsection_map_index(pfn),
213                                 subsection_map_index(pfn + pfns - 1));
214 
215                 pfn += pfns;
216                 nr_pages -= pfns;
217         }
218 }
219 #else
220 void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
221 {
222 }
223 #endif
224 
225 /* Record a memory area against a node. */
226 static void __init memory_present(int nid, unsigned long start, unsigned long end)
227 {
228         unsigned long pfn;
229 
230 #ifdef CONFIG_SPARSEMEM_EXTREME
231         if (unlikely(!mem_section)) {
232                 unsigned long size, align;
233 
234                 size = sizeof(struct mem_section *) * NR_SECTION_ROOTS;
235                 align = 1 << (INTERNODE_CACHE_SHIFT);
236                 mem_section = memblock_alloc(size, align);
237                 if (!mem_section)
238                         panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
239                               __func__, size, align);
240         }
241 #endif
242 
243         start &= PAGE_SECTION_MASK;
244         mminit_validate_memmodel_limits(&start, &end);
245         for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
246                 unsigned long section = pfn_to_section_nr(pfn);
247                 struct mem_section *ms;
248 
249                 sparse_index_init(section, nid);
250                 set_section_nid(section, nid);
251 
252                 ms = __nr_to_section(section);
253                 if (!ms->section_mem_map) {
254                         ms->section_mem_map = sparse_encode_early_nid(nid) |
255                                                         SECTION_IS_ONLINE;
256                         __section_mark_present(ms, section);
257                 }
258         }
259 }
260 
261 /*
262  * Mark all memblocks as present using memory_present().
263  * This is a convenience function that is useful to mark all of the systems
264  * memory as present during initialization.
265  */
266 static void __init memblocks_present(void)
267 {
268         unsigned long start, end;
269         int i, nid;
270 
271         for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, &nid)
272                 memory_present(nid, start, end);
273 }
274 
275 /*
276  * Subtle, we encode the real pfn into the mem_map such that
277  * the identity pfn - section_mem_map will return the actual
278  * physical page frame number.
279  */
280 static unsigned long sparse_encode_mem_map(struct page *mem_map, unsigned long pnum)
281 {
282         unsigned long coded_mem_map =
283                 (unsigned long)(mem_map - (section_nr_to_pfn(pnum)));
284         BUILD_BUG_ON(SECTION_MAP_LAST_BIT > PFN_SECTION_SHIFT);
285         BUG_ON(coded_mem_map & ~SECTION_MAP_MASK);
286         return coded_mem_map;
287 }
288 
289 #ifdef CONFIG_MEMORY_HOTPLUG
290 /*
291  * Decode mem_map from the coded memmap
292  */
293 struct page *sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long pnum)
294 {
295         /* mask off the extra low bits of information */
296         coded_mem_map &= SECTION_MAP_MASK;
297         return ((struct page *)coded_mem_map) + section_nr_to_pfn(pnum);
298 }
299 #endif /* CONFIG_MEMORY_HOTPLUG */
300 
301 static void __meminit sparse_init_one_section(struct mem_section *ms,
302                 unsigned long pnum, struct page *mem_map,
303                 struct mem_section_usage *usage, unsigned long flags)
304 {
305         ms->section_mem_map &= ~SECTION_MAP_MASK;
306         ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum)
307                 | SECTION_HAS_MEM_MAP | flags;
308         ms->usage = usage;
309 }
310 
311 static unsigned long usemap_size(void)
312 {
313         return BITS_TO_LONGS(SECTION_BLOCKFLAGS_BITS) * sizeof(unsigned long);
314 }
315 
316 size_t mem_section_usage_size(void)
317 {
318         return sizeof(struct mem_section_usage) + usemap_size();
319 }
320 
321 static inline phys_addr_t pgdat_to_phys(struct pglist_data *pgdat)
322 {
323 #ifndef CONFIG_NUMA
324         VM_BUG_ON(pgdat != &contig_page_data);
325         return __pa_symbol(&contig_page_data);
326 #else
327         return __pa(pgdat);
328 #endif
329 }
330 
331 #ifdef CONFIG_MEMORY_HOTREMOVE
332 static struct mem_section_usage * __init
333 sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
334                                          unsigned long size)
335 {
336         struct mem_section_usage *usage;
337         unsigned long goal, limit;
338         int nid;
339         /*
340          * A page may contain usemaps for other sections preventing the
341          * page being freed and making a section unremovable while
342          * other sections referencing the usemap remain active. Similarly,
343          * a pgdat can prevent a section being removed. If section A
344          * contains a pgdat and section B contains the usemap, both
345          * sections become inter-dependent. This allocates usemaps
346          * from the same section as the pgdat where possible to avoid
347          * this problem.
348          */
349         goal = pgdat_to_phys(pgdat) & (PAGE_SECTION_MASK << PAGE_SHIFT);
350         limit = goal + (1UL << PA_SECTION_SHIFT);
351         nid = early_pfn_to_nid(goal >> PAGE_SHIFT);
352 again:
353         usage = memblock_alloc_try_nid(size, SMP_CACHE_BYTES, goal, limit, nid);
354         if (!usage && limit) {
355                 limit = 0;
356                 goto again;
357         }
358         return usage;
359 }
360 
361 static void __init check_usemap_section_nr(int nid,
362                 struct mem_section_usage *usage)
363 {
364         unsigned long usemap_snr, pgdat_snr;
365         static unsigned long old_usemap_snr;
366         static unsigned long old_pgdat_snr;
367         struct pglist_data *pgdat = NODE_DATA(nid);
368         int usemap_nid;
369 
370         /* First call */
371         if (!old_usemap_snr) {
372                 old_usemap_snr = NR_MEM_SECTIONS;
373                 old_pgdat_snr = NR_MEM_SECTIONS;
374         }
375 
376         usemap_snr = pfn_to_section_nr(__pa(usage) >> PAGE_SHIFT);
377         pgdat_snr = pfn_to_section_nr(pgdat_to_phys(pgdat) >> PAGE_SHIFT);
378         if (usemap_snr == pgdat_snr)
379                 return;
380 
381         if (old_usemap_snr == usemap_snr && old_pgdat_snr == pgdat_snr)
382                 /* skip redundant message */
383                 return;
384 
385         old_usemap_snr = usemap_snr;
386         old_pgdat_snr = pgdat_snr;
387 
388         usemap_nid = sparse_early_nid(__nr_to_section(usemap_snr));
389         if (usemap_nid != nid) {
390                 pr_info("node %d must be removed before remove section %ld\n",
391                         nid, usemap_snr);
392                 return;
393         }
394         /*
395          * There is a circular dependency.
396          * Some platforms allow un-removable section because they will just
397          * gather other removable sections for dynamic partitioning.
398          * Just notify un-removable section's number here.
399          */
400         pr_info("Section %ld and %ld (node %d) have a circular dependency on usemap and pgdat allocations\n",
401                 usemap_snr, pgdat_snr, nid);
402 }
403 #else
404 static struct mem_section_usage * __init
405 sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
406                                          unsigned long size)
407 {
408         return memblock_alloc_node(size, SMP_CACHE_BYTES, pgdat->node_id);
409 }
410 
411 static void __init check_usemap_section_nr(int nid,
412                 struct mem_section_usage *usage)
413 {
414 }
415 #endif /* CONFIG_MEMORY_HOTREMOVE */
416 
417 #ifdef CONFIG_SPARSEMEM_VMEMMAP
418 static unsigned long __init section_map_size(void)
419 {
420         return ALIGN(sizeof(struct page) * PAGES_PER_SECTION, PMD_SIZE);
421 }
422 
423 #else
424 static unsigned long __init section_map_size(void)
425 {
426         return PAGE_ALIGN(sizeof(struct page) * PAGES_PER_SECTION);
427 }
428 
429 struct page __init *__populate_section_memmap(unsigned long pfn,
430                 unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
431                 struct dev_pagemap *pgmap)
432 {
433         unsigned long size = section_map_size();
434         struct page *map = sparse_buffer_alloc(size);
435         phys_addr_t addr = __pa(MAX_DMA_ADDRESS);
436 
437         if (map)
438                 return map;
439 
440         map = memmap_alloc(size, size, addr, nid, false);
441         if (!map)
442                 panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%pa\n",
443                       __func__, size, PAGE_SIZE, nid, &addr);
444 
445         return map;
446 }
447 #endif /* !CONFIG_SPARSEMEM_VMEMMAP */
448 
449 static void *sparsemap_buf __meminitdata;
450 static void *sparsemap_buf_end __meminitdata;
451 
452 static inline void __meminit sparse_buffer_free(unsigned long size)
453 {
454         WARN_ON(!sparsemap_buf || size == 0);
455         memblock_free(sparsemap_buf, size);
456 }
457 
458 static void __init sparse_buffer_init(unsigned long size, int nid)
459 {
460         phys_addr_t addr = __pa(MAX_DMA_ADDRESS);
461         WARN_ON(sparsemap_buf); /* forgot to call sparse_buffer_fini()? */
462         /*
463          * Pre-allocated buffer is mainly used by __populate_section_memmap
464          * and we want it to be properly aligned to the section size - this is
465          * especially the case for VMEMMAP which maps memmap to PMDs
466          */
467         sparsemap_buf = memmap_alloc(size, section_map_size(), addr, nid, true);
468         sparsemap_buf_end = sparsemap_buf + size;
469 }
470 
471 static void __init sparse_buffer_fini(void)
472 {
473         unsigned long size = sparsemap_buf_end - sparsemap_buf;
474 
475         if (sparsemap_buf && size > 0)
476                 sparse_buffer_free(size);
477         sparsemap_buf = NULL;
478 }
479 
480 void * __meminit sparse_buffer_alloc(unsigned long size)
481 {
482         void *ptr = NULL;
483 
484         if (sparsemap_buf) {
485                 ptr = (void *) roundup((unsigned long)sparsemap_buf, size);
486                 if (ptr + size > sparsemap_buf_end)
487                         ptr = NULL;
488                 else {
489                         /* Free redundant aligned space */
490                         if ((unsigned long)(ptr - sparsemap_buf) > 0)
491                                 sparse_buffer_free((unsigned long)(ptr - sparsemap_buf));
492                         sparsemap_buf = ptr + size;
493                 }
494         }
495         return ptr;
496 }
497 
498 void __weak __meminit vmemmap_populate_print_last(void)
499 {
500 }
501 
502 /*
503  * Initialize sparse on a specific node. The node spans [pnum_begin, pnum_end)
504  * And number of present sections in this node is map_count.
505  */
506 static void __init sparse_init_nid(int nid, unsigned long pnum_begin,
507                                    unsigned long pnum_end,
508                                    unsigned long map_count)
509 {
510         struct mem_section_usage *usage;
511         unsigned long pnum;
512         struct page *map;
513 
514         usage = sparse_early_usemaps_alloc_pgdat_section(NODE_DATA(nid),
515                         mem_section_usage_size() * map_count);
516         if (!usage) {
517                 pr_err("%s: node[%d] usemap allocation failed", __func__, nid);
518                 goto failed;
519         }
520         sparse_buffer_init(map_count * section_map_size(), nid);
521         for_each_present_section_nr(pnum_begin, pnum) {
522                 unsigned long pfn = section_nr_to_pfn(pnum);
523 
524                 if (pnum >= pnum_end)
525                         break;
526 
527                 map = __populate_section_memmap(pfn, PAGES_PER_SECTION,
528                                 nid, NULL, NULL);
529                 if (!map) {
530                         pr_err("%s: node[%d] memory map backing failed. Some memory will not be available.",
531                                __func__, nid);
532                         pnum_begin = pnum;
533                         sparse_buffer_fini();
534                         goto failed;
535                 }
536                 check_usemap_section_nr(nid, usage);
537                 sparse_init_one_section(__nr_to_section(pnum), pnum, map, usage,
538                                 SECTION_IS_EARLY);
539                 usage = (void *) usage + mem_section_usage_size();
540         }
541         sparse_buffer_fini();
542         return;
543 failed:
544         /* We failed to allocate, mark all the following pnums as not present */
545         for_each_present_section_nr(pnum_begin, pnum) {
546                 struct mem_section *ms;
547 
548                 if (pnum >= pnum_end)
549                         break;
550                 ms = __nr_to_section(pnum);
551                 ms->section_mem_map = 0;
552         }
553 }
554 
555 /*
556  * Allocate the accumulated non-linear sections, allocate a mem_map
557  * for each and record the physical to section mapping.
558  */
559 void __init sparse_init(void)
560 {
561         unsigned long pnum_end, pnum_begin, map_count = 1;
562         int nid_begin;
563 
564         memblocks_present();
565 
566         pnum_begin = first_present_section_nr();
567         nid_begin = sparse_early_nid(__nr_to_section(pnum_begin));
568 
569         /* Setup pageblock_order for HUGETLB_PAGE_SIZE_VARIABLE */
570         set_pageblock_order();
571 
572         for_each_present_section_nr(pnum_begin + 1, pnum_end) {
573                 int nid = sparse_early_nid(__nr_to_section(pnum_end));
574 
575                 if (nid == nid_begin) {
576                         map_count++;
577                         continue;
578                 }
579                 /* Init node with sections in range [pnum_begin, pnum_end) */
580                 sparse_init_nid(nid_begin, pnum_begin, pnum_end, map_count);
581                 nid_begin = nid;
582                 pnum_begin = pnum_end;
583                 map_count = 1;
584         }
585         /* cover the last node */
586         sparse_init_nid(nid_begin, pnum_begin, pnum_end, map_count);
587         vmemmap_populate_print_last();
588 }
589 
590 #ifdef CONFIG_MEMORY_HOTPLUG
591 
592 /* Mark all memory sections within the pfn range as online */
593 void online_mem_sections(unsigned long start_pfn, unsigned long end_pfn)
594 {
595         unsigned long pfn;
596 
597         for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
598                 unsigned long section_nr = pfn_to_section_nr(pfn);
599                 struct mem_section *ms;
600 
601                 /* onlining code should never touch invalid ranges */
602                 if (WARN_ON(!valid_section_nr(section_nr)))
603                         continue;
604 
605                 ms = __nr_to_section(section_nr);
606                 ms->section_mem_map |= SECTION_IS_ONLINE;
607         }
608 }
609 
610 /* Mark all memory sections within the pfn range as offline */
611 void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn)
612 {
613         unsigned long pfn;
614 
615         for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
616                 unsigned long section_nr = pfn_to_section_nr(pfn);
617                 struct mem_section *ms;
618 
619                 /*
620                  * TODO this needs some double checking. Offlining code makes
621                  * sure to check pfn_valid but those checks might be just bogus
622                  */
623                 if (WARN_ON(!valid_section_nr(section_nr)))
624                         continue;
625 
626                 ms = __nr_to_section(section_nr);
627                 ms->section_mem_map &= ~SECTION_IS_ONLINE;
628         }
629 }
630 
631 #ifdef CONFIG_SPARSEMEM_VMEMMAP
632 static struct page * __meminit populate_section_memmap(unsigned long pfn,
633                 unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
634                 struct dev_pagemap *pgmap)
635 {
636         return __populate_section_memmap(pfn, nr_pages, nid, altmap, pgmap);
637 }
638 
639 static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
640                 struct vmem_altmap *altmap)
641 {
642         unsigned long start = (unsigned long) pfn_to_page(pfn);
643         unsigned long end = start + nr_pages * sizeof(struct page);
644 
645         vmemmap_free(start, end, altmap);
646 }
647 static void free_map_bootmem(struct page *memmap)
648 {
649         unsigned long start = (unsigned long)memmap;
650         unsigned long end = (unsigned long)(memmap + PAGES_PER_SECTION);
651 
652         vmemmap_free(start, end, NULL);
653 }
654 
655 static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
656 {
657         DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
658         DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
659         struct mem_section *ms = __pfn_to_section(pfn);
660         unsigned long *subsection_map = ms->usage
661                 ? &ms->usage->subsection_map[0] : NULL;
662 
663         subsection_mask_set(map, pfn, nr_pages);
664         if (subsection_map)
665                 bitmap_and(tmp, map, subsection_map, SUBSECTIONS_PER_SECTION);
666 
667         if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
668                                 "section already deactivated (%#lx + %ld)\n",
669                                 pfn, nr_pages))
670                 return -EINVAL;
671 
672         bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
673         return 0;
674 }
675 
676 static bool is_subsection_map_empty(struct mem_section *ms)
677 {
678         return bitmap_empty(&ms->usage->subsection_map[0],
679                             SUBSECTIONS_PER_SECTION);
680 }
681 
682 static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
683 {
684         struct mem_section *ms = __pfn_to_section(pfn);
685         DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
686         unsigned long *subsection_map;
687         int rc = 0;
688 
689         subsection_mask_set(map, pfn, nr_pages);
690 
691         subsection_map = &ms->usage->subsection_map[0];
692 
693         if (bitmap_empty(map, SUBSECTIONS_PER_SECTION))
694                 rc = -EINVAL;
695         else if (bitmap_intersects(map, subsection_map, SUBSECTIONS_PER_SECTION))
696                 rc = -EEXIST;
697         else
698                 bitmap_or(subsection_map, map, subsection_map,
699                                 SUBSECTIONS_PER_SECTION);
700 
701         return rc;
702 }
703 #else
704 struct page * __meminit populate_section_memmap(unsigned long pfn,
705                 unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
706                 struct dev_pagemap *pgmap)
707 {
708         return kvmalloc_node(array_size(sizeof(struct page),
709                                         PAGES_PER_SECTION), GFP_KERNEL, nid);
710 }
711 
712 static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
713                 struct vmem_altmap *altmap)
714 {
715         kvfree(pfn_to_page(pfn));
716 }
717 
718 static void free_map_bootmem(struct page *memmap)
719 {
720         unsigned long maps_section_nr, removing_section_nr, i;
721         unsigned long magic, nr_pages;
722         struct page *page = virt_to_page(memmap);
723 
724         nr_pages = PAGE_ALIGN(PAGES_PER_SECTION * sizeof(struct page))
725                 >> PAGE_SHIFT;
726 
727         for (i = 0; i < nr_pages; i++, page++) {
728                 magic = page->index;
729 
730                 BUG_ON(magic == NODE_INFO);
731 
732                 maps_section_nr = pfn_to_section_nr(page_to_pfn(page));
733                 removing_section_nr = page_private(page);
734 
735                 /*
736                  * When this function is called, the removing section is
737                  * logical offlined state. This means all pages are isolated
738                  * from page allocator. If removing section's memmap is placed
739                  * on the same section, it must not be freed.
740                  * If it is freed, page allocator may allocate it which will
741                  * be removed physically soon.
742                  */
743                 if (maps_section_nr != removing_section_nr)
744                         put_page_bootmem(page);
745         }
746 }
747 
748 static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
749 {
750         return 0;
751 }
752 
753 static bool is_subsection_map_empty(struct mem_section *ms)
754 {
755         return true;
756 }
757 
758 static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
759 {
760         return 0;
761 }
762 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
763 
764 /*
765  * To deactivate a memory region, there are 3 cases to handle across
766  * two configurations (SPARSEMEM_VMEMMAP={y,n}):
767  *
768  * 1. deactivation of a partial hot-added section (only possible in
769  *    the SPARSEMEM_VMEMMAP=y case).
770  *      a) section was present at memory init.
771  *      b) section was hot-added post memory init.
772  * 2. deactivation of a complete hot-added section.
773  * 3. deactivation of a complete section from memory init.
774  *
775  * For 1, when subsection_map does not empty we will not be freeing the
776  * usage map, but still need to free the vmemmap range.
777  *
778  * For 2 and 3, the SPARSEMEM_VMEMMAP={y,n} cases are unified
779  */
780 static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
781                 struct vmem_altmap *altmap)
782 {
783         struct mem_section *ms = __pfn_to_section(pfn);
784         bool section_is_early = early_section(ms);
785         struct page *memmap = NULL;
786         bool empty;
787 
788         if (clear_subsection_map(pfn, nr_pages))
789                 return;
790 
791         empty = is_subsection_map_empty(ms);
792         if (empty) {
793                 unsigned long section_nr = pfn_to_section_nr(pfn);
794 
795                 /*
796                  * When removing an early section, the usage map is kept (as the
797                  * usage maps of other sections fall into the same page). It
798                  * will be re-used when re-adding the section - which is then no
799                  * longer an early section. If the usage map is PageReserved, it
800                  * was allocated during boot.
801                  */
802                 if (!PageReserved(virt_to_page(ms->usage))) {
803                         kfree(ms->usage);
804                         ms->usage = NULL;
805                 }
806                 memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
807                 /*
808                  * Mark the section invalid so that valid_section()
809                  * return false. This prevents code from dereferencing
810                  * ms->usage array.
811                  */
812                 ms->section_mem_map &= ~SECTION_HAS_MEM_MAP;
813         }
814 
815         /*
816          * The memmap of early sections is always fully populated. See
817          * section_activate() and pfn_valid() .
818          */
819         if (!section_is_early)
820                 depopulate_section_memmap(pfn, nr_pages, altmap);
821         else if (memmap)
822                 free_map_bootmem(memmap);
823 
824         if (empty)
825                 ms->section_mem_map = (unsigned long)NULL;
826 }
827 
828 static struct page * __meminit section_activate(int nid, unsigned long pfn,
829                 unsigned long nr_pages, struct vmem_altmap *altmap,
830                 struct dev_pagemap *pgmap)
831 {
832         struct mem_section *ms = __pfn_to_section(pfn);
833         struct mem_section_usage *usage = NULL;
834         struct page *memmap;
835         int rc = 0;
836 
837         if (!ms->usage) {
838                 usage = kzalloc(mem_section_usage_size(), GFP_KERNEL);
839                 if (!usage)
840                         return ERR_PTR(-ENOMEM);
841                 ms->usage = usage;
842         }
843 
844         rc = fill_subsection_map(pfn, nr_pages);
845         if (rc) {
846                 if (usage)
847                         ms->usage = NULL;
848                 kfree(usage);
849                 return ERR_PTR(rc);
850         }
851 
852         /*
853          * The early init code does not consider partially populated
854          * initial sections, it simply assumes that memory will never be
855          * referenced.  If we hot-add memory into such a section then we
856          * do not need to populate the memmap and can simply reuse what
857          * is already there.
858          */
859         if (nr_pages < PAGES_PER_SECTION && early_section(ms))
860                 return pfn_to_page(pfn);
861 
862         memmap = populate_section_memmap(pfn, nr_pages, nid, altmap, pgmap);
863         if (!memmap) {
864                 section_deactivate(pfn, nr_pages, altmap);
865                 return ERR_PTR(-ENOMEM);
866         }
867 
868         return memmap;
869 }
870 
871 /**
872  * sparse_add_section - add a memory section, or populate an existing one
873  * @nid: The node to add section on
874  * @start_pfn: start pfn of the memory range
875  * @nr_pages: number of pfns to add in the section
876  * @altmap: alternate pfns to allocate the memmap backing store
877  * @pgmap: alternate compound page geometry for devmap mappings
878  *
879  * This is only intended for hotplug.
880  *
881  * Note that only VMEMMAP supports sub-section aligned hotplug,
882  * the proper alignment and size are gated by check_pfn_span().
883  *
884  *
885  * Return:
886  * * 0          - On success.
887  * * -EEXIST    - Section has been present.
888  * * -ENOMEM    - Out of memory.
889  */
890 int __meminit sparse_add_section(int nid, unsigned long start_pfn,
891                 unsigned long nr_pages, struct vmem_altmap *altmap,
892                 struct dev_pagemap *pgmap)
893 {
894         unsigned long section_nr = pfn_to_section_nr(start_pfn);
895         struct mem_section *ms;
896         struct page *memmap;
897         int ret;
898 
899         ret = sparse_index_init(section_nr, nid);
900         if (ret < 0)
901                 return ret;
902 
903         memmap = section_activate(nid, start_pfn, nr_pages, altmap, pgmap);
904         if (IS_ERR(memmap))
905                 return PTR_ERR(memmap);
906 
907         /*
908          * Poison uninitialized struct pages in order to catch invalid flags
909          * combinations.
910          */
911         page_init_poison(memmap, sizeof(struct page) * nr_pages);
912 
913         ms = __nr_to_section(section_nr);
914         set_section_nid(section_nr, nid);
915         __section_mark_present(ms, section_nr);
916 
917         /* Align memmap to section boundary in the subsection case */
918         if (section_nr_to_pfn(section_nr) != start_pfn)
919                 memmap = pfn_to_page(section_nr_to_pfn(section_nr));
920         sparse_init_one_section(ms, section_nr, memmap, ms->usage, 0);
921 
922         return 0;
923 }
924 
925 void sparse_remove_section(struct mem_section *ms, unsigned long pfn,
926                 unsigned long nr_pages, unsigned long map_offset,
927                 struct vmem_altmap *altmap)
928 {
929         clear_hwpoisoned_pages(pfn_to_page(pfn) + map_offset,
930                         nr_pages - map_offset);
931         section_deactivate(pfn, nr_pages, altmap);
932 }
933 #endif /* CONFIG_MEMORY_HOTPLUG */
934 

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