1
2
3
4
5
6
7
8
9
10#include <linux/mm.h>
11#include <linux/gfp.h>
12#include <linux/kernel_stat.h>
13#include <linux/swap.h>
14#include <linux/swapops.h>
15#include <linux/init.h>
16#include <linux/pagemap.h>
17#include <linux/backing-dev.h>
18#include <linux/blkdev.h>
19#include <linux/pagevec.h>
20#include <linux/migrate.h>
21#include <linux/vmalloc.h>
22#include <linux/swap_slots.h>
23#include <linux/huge_mm.h>
24#include <linux/shmem_fs.h>
25#include "internal.h"
26
27
28
29
30
31static const struct address_space_operations swap_aops = {
32 .writepage = swap_writepage,
33 .set_page_dirty = swap_set_page_dirty,
34#ifdef CONFIG_MIGRATION
35 .migratepage = migrate_page,
36#endif
37};
38
39struct address_space *swapper_spaces[MAX_SWAPFILES] __read_mostly;
40static unsigned int nr_swapper_spaces[MAX_SWAPFILES] __read_mostly;
41static bool enable_vma_readahead __read_mostly = true;
42
43#define SWAP_RA_WIN_SHIFT (PAGE_SHIFT / 2)
44#define SWAP_RA_HITS_MASK ((1UL << SWAP_RA_WIN_SHIFT) - 1)
45#define SWAP_RA_HITS_MAX SWAP_RA_HITS_MASK
46#define SWAP_RA_WIN_MASK (~PAGE_MASK & ~SWAP_RA_HITS_MASK)
47
48#define SWAP_RA_HITS(v) ((v) & SWAP_RA_HITS_MASK)
49#define SWAP_RA_WIN(v) (((v) & SWAP_RA_WIN_MASK) >> SWAP_RA_WIN_SHIFT)
50#define SWAP_RA_ADDR(v) ((v) & PAGE_MASK)
51
52#define SWAP_RA_VAL(addr, win, hits) \
53 (((addr) & PAGE_MASK) | \
54 (((win) << SWAP_RA_WIN_SHIFT) & SWAP_RA_WIN_MASK) | \
55 ((hits) & SWAP_RA_HITS_MASK))
56
57
58#define GET_SWAP_RA_VAL(vma) \
59 (atomic_long_read(&(vma)->swap_readahead_info) ? : 4)
60
61#define INC_CACHE_INFO(x) data_race(swap_cache_info.x++)
62#define ADD_CACHE_INFO(x, nr) data_race(swap_cache_info.x += (nr))
63
64static struct {
65 unsigned long add_total;
66 unsigned long del_total;
67 unsigned long find_success;
68 unsigned long find_total;
69} swap_cache_info;
70
71static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);
72
73void show_swap_cache_info(void)
74{
75 printk("%lu pages in swap cache\n", total_swapcache_pages());
76 printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
77 swap_cache_info.add_total, swap_cache_info.del_total,
78 swap_cache_info.find_success, swap_cache_info.find_total);
79 printk("Free swap = %ldkB\n",
80 get_nr_swap_pages() << (PAGE_SHIFT - 10));
81 printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
82}
83
84void *get_shadow_from_swap_cache(swp_entry_t entry)
85{
86 struct address_space *address_space = swap_address_space(entry);
87 pgoff_t idx = swp_offset(entry);
88 struct page *page;
89
90 page = xa_load(&address_space->i_pages, idx);
91 if (xa_is_value(page))
92 return page;
93 return NULL;
94}
95
96
97
98
99
100int add_to_swap_cache(struct page *page, swp_entry_t entry,
101 gfp_t gfp, void **shadowp)
102{
103 struct address_space *address_space = swap_address_space(entry);
104 pgoff_t idx = swp_offset(entry);
105 XA_STATE_ORDER(xas, &address_space->i_pages, idx, compound_order(page));
106 unsigned long i, nr = thp_nr_pages(page);
107 void *old;
108
109 VM_BUG_ON_PAGE(!PageLocked(page), page);
110 VM_BUG_ON_PAGE(PageSwapCache(page), page);
111 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
112
113 page_ref_add(page, nr);
114 SetPageSwapCache(page);
115
116 do {
117 xas_lock_irq(&xas);
118 xas_create_range(&xas);
119 if (xas_error(&xas))
120 goto unlock;
121 for (i = 0; i < nr; i++) {
122 VM_BUG_ON_PAGE(xas.xa_index != idx + i, page);
123 old = xas_load(&xas);
124 if (xa_is_value(old)) {
125 if (shadowp)
126 *shadowp = old;
127 }
128 set_page_private(page + i, entry.val + i);
129 xas_store(&xas, page);
130 xas_next(&xas);
131 }
132 address_space->nrpages += nr;
133 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
134 __mod_lruvec_page_state(page, NR_SWAPCACHE, nr);
135 ADD_CACHE_INFO(add_total, nr);
136unlock:
137 xas_unlock_irq(&xas);
138 } while (xas_nomem(&xas, gfp));
139
140 if (!xas_error(&xas))
141 return 0;
142
143 ClearPageSwapCache(page);
144 page_ref_sub(page, nr);
145 return xas_error(&xas);
146}
147
148
149
150
151
152void __delete_from_swap_cache(struct page *page,
153 swp_entry_t entry, void *shadow)
154{
155 struct address_space *address_space = swap_address_space(entry);
156 int i, nr = thp_nr_pages(page);
157 pgoff_t idx = swp_offset(entry);
158 XA_STATE(xas, &address_space->i_pages, idx);
159
160 VM_BUG_ON_PAGE(!PageLocked(page), page);
161 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
162 VM_BUG_ON_PAGE(PageWriteback(page), page);
163
164 for (i = 0; i < nr; i++) {
165 void *entry = xas_store(&xas, shadow);
166 VM_BUG_ON_PAGE(entry != page, entry);
167 set_page_private(page + i, 0);
168 xas_next(&xas);
169 }
170 ClearPageSwapCache(page);
171 address_space->nrpages -= nr;
172 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
173 __mod_lruvec_page_state(page, NR_SWAPCACHE, -nr);
174 ADD_CACHE_INFO(del_total, nr);
175}
176
177
178
179
180
181
182
183
184int add_to_swap(struct page *page)
185{
186 swp_entry_t entry;
187 int err;
188
189 VM_BUG_ON_PAGE(!PageLocked(page), page);
190 VM_BUG_ON_PAGE(!PageUptodate(page), page);
191
192 entry = get_swap_page(page);
193 if (!entry.val)
194 return 0;
195
196
197
198
199
200
201
202
203
204
205
206
207 err = add_to_swap_cache(page, entry,
208 __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN, NULL);
209 if (err)
210
211
212
213
214 goto fail;
215
216
217
218
219
220
221
222
223
224
225 set_page_dirty(page);
226
227 return 1;
228
229fail:
230 put_swap_page(page, entry);
231 return 0;
232}
233
234
235
236
237
238
239
240void delete_from_swap_cache(struct page *page)
241{
242 swp_entry_t entry = { .val = page_private(page) };
243 struct address_space *address_space = swap_address_space(entry);
244
245 xa_lock_irq(&address_space->i_pages);
246 __delete_from_swap_cache(page, entry, NULL);
247 xa_unlock_irq(&address_space->i_pages);
248
249 put_swap_page(page, entry);
250 page_ref_sub(page, thp_nr_pages(page));
251}
252
253void clear_shadow_from_swap_cache(int type, unsigned long begin,
254 unsigned long end)
255{
256 unsigned long curr = begin;
257 void *old;
258
259 for (;;) {
260 swp_entry_t entry = swp_entry(type, curr);
261 struct address_space *address_space = swap_address_space(entry);
262 XA_STATE(xas, &address_space->i_pages, curr);
263
264 xa_lock_irq(&address_space->i_pages);
265 xas_for_each(&xas, old, end) {
266 if (!xa_is_value(old))
267 continue;
268 xas_store(&xas, NULL);
269 }
270 xa_unlock_irq(&address_space->i_pages);
271
272
273 curr >>= SWAP_ADDRESS_SPACE_SHIFT;
274 curr++;
275 curr <<= SWAP_ADDRESS_SPACE_SHIFT;
276 if (curr > end)
277 break;
278 }
279}
280
281
282
283
284
285
286
287
288
289void free_swap_cache(struct page *page)
290{
291 if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) {
292 try_to_free_swap(page);
293 unlock_page(page);
294 }
295}
296
297
298
299
300
301void free_page_and_swap_cache(struct page *page)
302{
303 free_swap_cache(page);
304 if (!is_huge_zero_page(page))
305 put_page(page);
306}
307
308
309
310
311
312void free_pages_and_swap_cache(struct page **pages, int nr)
313{
314 struct page **pagep = pages;
315 int i;
316
317 lru_add_drain();
318 for (i = 0; i < nr; i++)
319 free_swap_cache(pagep[i]);
320 release_pages(pagep, nr);
321}
322
323static inline bool swap_use_vma_readahead(void)
324{
325 return READ_ONCE(enable_vma_readahead) && !atomic_read(&nr_rotate_swap);
326}
327
328
329
330
331
332
333
334struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
335 unsigned long addr)
336{
337 struct page *page;
338 struct swap_info_struct *si;
339
340 si = get_swap_device(entry);
341 if (!si)
342 return NULL;
343 page = find_get_page(swap_address_space(entry), swp_offset(entry));
344 put_swap_device(si);
345
346 INC_CACHE_INFO(find_total);
347 if (page) {
348 bool vma_ra = swap_use_vma_readahead();
349 bool readahead;
350
351 INC_CACHE_INFO(find_success);
352
353
354
355
356 if (unlikely(PageTransCompound(page)))
357 return page;
358
359 readahead = TestClearPageReadahead(page);
360 if (vma && vma_ra) {
361 unsigned long ra_val;
362 int win, hits;
363
364 ra_val = GET_SWAP_RA_VAL(vma);
365 win = SWAP_RA_WIN(ra_val);
366 hits = SWAP_RA_HITS(ra_val);
367 if (readahead)
368 hits = min_t(int, hits + 1, SWAP_RA_HITS_MAX);
369 atomic_long_set(&vma->swap_readahead_info,
370 SWAP_RA_VAL(addr, win, hits));
371 }
372
373 if (readahead) {
374 count_vm_event(SWAP_RA_HIT);
375 if (!vma || !vma_ra)
376 atomic_inc(&swapin_readahead_hits);
377 }
378 }
379
380 return page;
381}
382
383
384
385
386
387
388
389
390
391
392
393struct page *find_get_incore_page(struct address_space *mapping, pgoff_t index)
394{
395 swp_entry_t swp;
396 struct swap_info_struct *si;
397 struct page *page = pagecache_get_page(mapping, index,
398 FGP_ENTRY | FGP_HEAD, 0);
399
400 if (!page)
401 return page;
402 if (!xa_is_value(page))
403 return find_subpage(page, index);
404 if (!shmem_mapping(mapping))
405 return NULL;
406
407 swp = radix_to_swp_entry(page);
408
409 si = get_swap_device(swp);
410 if (!si)
411 return NULL;
412 page = find_get_page(swap_address_space(swp), swp_offset(swp));
413 put_swap_device(si);
414 return page;
415}
416
417struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
418 struct vm_area_struct *vma, unsigned long addr,
419 bool *new_page_allocated)
420{
421 struct swap_info_struct *si;
422 struct page *page;
423 void *shadow = NULL;
424
425 *new_page_allocated = false;
426
427 for (;;) {
428 int err;
429
430
431
432
433
434 si = get_swap_device(entry);
435 if (!si)
436 return NULL;
437 page = find_get_page(swap_address_space(entry),
438 swp_offset(entry));
439 put_swap_device(si);
440 if (page)
441 return page;
442
443
444
445
446
447
448
449
450
451 if (!__swp_swapcount(entry) && swap_slot_cache_enabled)
452 return NULL;
453
454
455
456
457
458
459 page = alloc_page_vma(gfp_mask, vma, addr);
460 if (!page)
461 return NULL;
462
463
464
465
466 err = swapcache_prepare(entry);
467 if (!err)
468 break;
469
470 put_page(page);
471 if (err != -EEXIST)
472 return NULL;
473
474
475
476
477
478
479
480
481 schedule_timeout_uninterruptible(1);
482 }
483
484
485
486
487
488 __SetPageLocked(page);
489 __SetPageSwapBacked(page);
490
491 if (mem_cgroup_swapin_charge_page(page, NULL, gfp_mask, entry))
492 goto fail_unlock;
493
494
495 if (add_to_swap_cache(page, entry, gfp_mask & GFP_RECLAIM_MASK, &shadow))
496 goto fail_unlock;
497
498 mem_cgroup_swapin_uncharge_swap(entry);
499
500 if (shadow)
501 workingset_refault(page_folio(page), shadow);
502
503
504 lru_cache_add(page);
505 *new_page_allocated = true;
506 return page;
507
508fail_unlock:
509 put_swap_page(page, entry);
510 unlock_page(page);
511 put_page(page);
512 return NULL;
513}
514
515
516
517
518
519
520
521struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
522 struct vm_area_struct *vma, unsigned long addr, bool do_poll)
523{
524 bool page_was_allocated;
525 struct page *retpage = __read_swap_cache_async(entry, gfp_mask,
526 vma, addr, &page_was_allocated);
527
528 if (page_was_allocated)
529 swap_readpage(retpage, do_poll);
530
531 return retpage;
532}
533
534static unsigned int __swapin_nr_pages(unsigned long prev_offset,
535 unsigned long offset,
536 int hits,
537 int max_pages,
538 int prev_win)
539{
540 unsigned int pages, last_ra;
541
542
543
544
545
546
547 pages = hits + 2;
548 if (pages == 2) {
549
550
551
552
553
554 if (offset != prev_offset + 1 && offset != prev_offset - 1)
555 pages = 1;
556 } else {
557 unsigned int roundup = 4;
558 while (roundup < pages)
559 roundup <<= 1;
560 pages = roundup;
561 }
562
563 if (pages > max_pages)
564 pages = max_pages;
565
566
567 last_ra = prev_win / 2;
568 if (pages < last_ra)
569 pages = last_ra;
570
571 return pages;
572}
573
574static unsigned long swapin_nr_pages(unsigned long offset)
575{
576 static unsigned long prev_offset;
577 unsigned int hits, pages, max_pages;
578 static atomic_t last_readahead_pages;
579
580 max_pages = 1 << READ_ONCE(page_cluster);
581 if (max_pages <= 1)
582 return 1;
583
584 hits = atomic_xchg(&swapin_readahead_hits, 0);
585 pages = __swapin_nr_pages(READ_ONCE(prev_offset), offset, hits,
586 max_pages,
587 atomic_read(&last_readahead_pages));
588 if (!hits)
589 WRITE_ONCE(prev_offset, offset);
590 atomic_set(&last_readahead_pages, pages);
591
592 return pages;
593}
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
614 struct vm_fault *vmf)
615{
616 struct page *page;
617 unsigned long entry_offset = swp_offset(entry);
618 unsigned long offset = entry_offset;
619 unsigned long start_offset, end_offset;
620 unsigned long mask;
621 struct swap_info_struct *si = swp_swap_info(entry);
622 struct blk_plug plug;
623 bool do_poll = true, page_allocated;
624 struct vm_area_struct *vma = vmf->vma;
625 unsigned long addr = vmf->address;
626
627 mask = swapin_nr_pages(offset) - 1;
628 if (!mask)
629 goto skip;
630
631 do_poll = false;
632
633 start_offset = offset & ~mask;
634 end_offset = offset | mask;
635 if (!start_offset)
636 start_offset++;
637 if (end_offset >= si->max)
638 end_offset = si->max - 1;
639
640 blk_start_plug(&plug);
641 for (offset = start_offset; offset <= end_offset ; offset++) {
642
643 page = __read_swap_cache_async(
644 swp_entry(swp_type(entry), offset),
645 gfp_mask, vma, addr, &page_allocated);
646 if (!page)
647 continue;
648 if (page_allocated) {
649 swap_readpage(page, false);
650 if (offset != entry_offset) {
651 SetPageReadahead(page);
652 count_vm_event(SWAP_RA);
653 }
654 }
655 put_page(page);
656 }
657 blk_finish_plug(&plug);
658
659 lru_add_drain();
660skip:
661 return read_swap_cache_async(entry, gfp_mask, vma, addr, do_poll);
662}
663
664int init_swap_address_space(unsigned int type, unsigned long nr_pages)
665{
666 struct address_space *spaces, *space;
667 unsigned int i, nr;
668
669 nr = DIV_ROUND_UP(nr_pages, SWAP_ADDRESS_SPACE_PAGES);
670 spaces = kvcalloc(nr, sizeof(struct address_space), GFP_KERNEL);
671 if (!spaces)
672 return -ENOMEM;
673 for (i = 0; i < nr; i++) {
674 space = spaces + i;
675 xa_init_flags(&space->i_pages, XA_FLAGS_LOCK_IRQ);
676 atomic_set(&space->i_mmap_writable, 0);
677 space->a_ops = &swap_aops;
678
679 mapping_set_no_writeback_tags(space);
680 }
681 nr_swapper_spaces[type] = nr;
682 swapper_spaces[type] = spaces;
683
684 return 0;
685}
686
687void exit_swap_address_space(unsigned int type)
688{
689 int i;
690 struct address_space *spaces = swapper_spaces[type];
691
692 for (i = 0; i < nr_swapper_spaces[type]; i++)
693 VM_WARN_ON_ONCE(!mapping_empty(&spaces[i]));
694 kvfree(spaces);
695 nr_swapper_spaces[type] = 0;
696 swapper_spaces[type] = NULL;
697}
698
699static inline void swap_ra_clamp_pfn(struct vm_area_struct *vma,
700 unsigned long faddr,
701 unsigned long lpfn,
702 unsigned long rpfn,
703 unsigned long *start,
704 unsigned long *end)
705{
706 *start = max3(lpfn, PFN_DOWN(vma->vm_start),
707 PFN_DOWN(faddr & PMD_MASK));
708 *end = min3(rpfn, PFN_DOWN(vma->vm_end),
709 PFN_DOWN((faddr & PMD_MASK) + PMD_SIZE));
710}
711
712static void swap_ra_info(struct vm_fault *vmf,
713 struct vma_swap_readahead *ra_info)
714{
715 struct vm_area_struct *vma = vmf->vma;
716 unsigned long ra_val;
717 unsigned long faddr, pfn, fpfn;
718 unsigned long start, end;
719 pte_t *pte, *orig_pte;
720 unsigned int max_win, hits, prev_win, win, left;
721#ifndef CONFIG_64BIT
722 pte_t *tpte;
723#endif
724
725 max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster),
726 SWAP_RA_ORDER_CEILING);
727 if (max_win == 1) {
728 ra_info->win = 1;
729 return;
730 }
731
732 faddr = vmf->address;
733 orig_pte = pte = pte_offset_map(vmf->pmd, faddr);
734
735 fpfn = PFN_DOWN(faddr);
736 ra_val = GET_SWAP_RA_VAL(vma);
737 pfn = PFN_DOWN(SWAP_RA_ADDR(ra_val));
738 prev_win = SWAP_RA_WIN(ra_val);
739 hits = SWAP_RA_HITS(ra_val);
740 ra_info->win = win = __swapin_nr_pages(pfn, fpfn, hits,
741 max_win, prev_win);
742 atomic_long_set(&vma->swap_readahead_info,
743 SWAP_RA_VAL(faddr, win, 0));
744
745 if (win == 1) {
746 pte_unmap(orig_pte);
747 return;
748 }
749
750
751 if (fpfn == pfn + 1)
752 swap_ra_clamp_pfn(vma, faddr, fpfn, fpfn + win, &start, &end);
753 else if (pfn == fpfn + 1)
754 swap_ra_clamp_pfn(vma, faddr, fpfn - win + 1, fpfn + 1,
755 &start, &end);
756 else {
757 left = (win - 1) / 2;
758 swap_ra_clamp_pfn(vma, faddr, fpfn - left, fpfn + win - left,
759 &start, &end);
760 }
761 ra_info->nr_pte = end - start;
762 ra_info->offset = fpfn - start;
763 pte -= ra_info->offset;
764#ifdef CONFIG_64BIT
765 ra_info->ptes = pte;
766#else
767 tpte = ra_info->ptes;
768 for (pfn = start; pfn != end; pfn++)
769 *tpte++ = *pte++;
770#endif
771 pte_unmap(orig_pte);
772}
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask,
789 struct vm_fault *vmf)
790{
791 struct blk_plug plug;
792 struct vm_area_struct *vma = vmf->vma;
793 struct page *page;
794 pte_t *pte, pentry;
795 swp_entry_t entry;
796 unsigned int i;
797 bool page_allocated;
798 struct vma_swap_readahead ra_info = {
799 .win = 1,
800 };
801
802 swap_ra_info(vmf, &ra_info);
803 if (ra_info.win == 1)
804 goto skip;
805
806 blk_start_plug(&plug);
807 for (i = 0, pte = ra_info.ptes; i < ra_info.nr_pte;
808 i++, pte++) {
809 pentry = *pte;
810 if (pte_none(pentry))
811 continue;
812 if (pte_present(pentry))
813 continue;
814 entry = pte_to_swp_entry(pentry);
815 if (unlikely(non_swap_entry(entry)))
816 continue;
817 page = __read_swap_cache_async(entry, gfp_mask, vma,
818 vmf->address, &page_allocated);
819 if (!page)
820 continue;
821 if (page_allocated) {
822 swap_readpage(page, false);
823 if (i != ra_info.offset) {
824 SetPageReadahead(page);
825 count_vm_event(SWAP_RA);
826 }
827 }
828 put_page(page);
829 }
830 blk_finish_plug(&plug);
831 lru_add_drain();
832skip:
833 return read_swap_cache_async(fentry, gfp_mask, vma, vmf->address,
834 ra_info.win == 1);
835}
836
837
838
839
840
841
842
843
844
845
846
847
848
849struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
850 struct vm_fault *vmf)
851{
852 return swap_use_vma_readahead() ?
853 swap_vma_readahead(entry, gfp_mask, vmf) :
854 swap_cluster_readahead(entry, gfp_mask, vmf);
855}
856
857#ifdef CONFIG_SYSFS
858static ssize_t vma_ra_enabled_show(struct kobject *kobj,
859 struct kobj_attribute *attr, char *buf)
860{
861 return sysfs_emit(buf, "%s\n",
862 enable_vma_readahead ? "true" : "false");
863}
864static ssize_t vma_ra_enabled_store(struct kobject *kobj,
865 struct kobj_attribute *attr,
866 const char *buf, size_t count)
867{
868 if (!strncmp(buf, "true", 4) || !strncmp(buf, "1", 1))
869 enable_vma_readahead = true;
870 else if (!strncmp(buf, "false", 5) || !strncmp(buf, "0", 1))
871 enable_vma_readahead = false;
872 else
873 return -EINVAL;
874
875 return count;
876}
877static struct kobj_attribute vma_ra_enabled_attr =
878 __ATTR(vma_ra_enabled, 0644, vma_ra_enabled_show,
879 vma_ra_enabled_store);
880
881static struct attribute *swap_attrs[] = {
882 &vma_ra_enabled_attr.attr,
883 NULL,
884};
885
886static const struct attribute_group swap_attr_group = {
887 .attrs = swap_attrs,
888};
889
890static int __init swap_init_sysfs(void)
891{
892 int err;
893 struct kobject *swap_kobj;
894
895 swap_kobj = kobject_create_and_add("swap", mm_kobj);
896 if (!swap_kobj) {
897 pr_err("failed to create swap kobject\n");
898 return -ENOMEM;
899 }
900 err = sysfs_create_group(swap_kobj, &swap_attr_group);
901 if (err) {
902 pr_err("failed to register swap group\n");
903 goto delete_obj;
904 }
905 return 0;
906
907delete_obj:
908 kobject_put(swap_kobj);
909 return err;
910}
911subsys_initcall(swap_init_sysfs);
912#endif
913