2 * linux/mm/swap_state.c
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 * Swap reorganised 29.12.95, Stephen Tweedie
7 * Rewritten to use page cache, (C) 1998 Stephen Tweedie
10 #include <linux/gfp.h>
11 #include <linux/kernel_stat.h>
12 #include <linux/swap.h>
13 #include <linux/swapops.h>
14 #include <linux/init.h>
15 #include <linux/pagemap.h>
16 #include <linux/backing-dev.h>
17 #include <linux/blkdev.h>
18 #include <linux/pagevec.h>
19 #include <linux/migrate.h>
20 #include <linux/vmalloc.h>
21 #include <linux/swap_slots.h>
22 #include <linux/huge_mm.h>
24 #include <asm/pgtable.h>
27 * swapper_space is a fiction, retained to simplify the path through
28 * vmscan's shrink_page_list.
30 static const struct address_space_operations swap_aops
= {
31 .writepage
= swap_writepage
,
32 .set_page_dirty
= swap_set_page_dirty
,
33 #ifdef CONFIG_MIGRATION
34 .migratepage
= migrate_page
,
38 struct address_space
*swapper_spaces
[MAX_SWAPFILES
];
39 static unsigned int nr_swapper_spaces
[MAX_SWAPFILES
];
40 bool swap_vma_readahead
= true;
42 #define SWAP_RA_MAX_ORDER_DEFAULT 3
44 static int swap_ra_max_order
= SWAP_RA_MAX_ORDER_DEFAULT
;
46 #define SWAP_RA_WIN_SHIFT (PAGE_SHIFT / 2)
47 #define SWAP_RA_HITS_MASK ((1UL << SWAP_RA_WIN_SHIFT) - 1)
48 #define SWAP_RA_HITS_MAX SWAP_RA_HITS_MASK
49 #define SWAP_RA_WIN_MASK (~PAGE_MASK & ~SWAP_RA_HITS_MASK)
51 #define SWAP_RA_HITS(v) ((v) & SWAP_RA_HITS_MASK)
52 #define SWAP_RA_WIN(v) (((v) & SWAP_RA_WIN_MASK) >> SWAP_RA_WIN_SHIFT)
53 #define SWAP_RA_ADDR(v) ((v) & PAGE_MASK)
55 #define SWAP_RA_VAL(addr, win, hits) \
56 (((addr) & PAGE_MASK) | \
57 (((win) << SWAP_RA_WIN_SHIFT) & SWAP_RA_WIN_MASK) | \
58 ((hits) & SWAP_RA_HITS_MASK))
60 /* Initial readahead hits is 4 to start up with a small window */
61 #define GET_SWAP_RA_VAL(vma) \
62 (atomic_long_read(&(vma)->swap_readahead_info) ? : 4)
64 #define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0)
65 #define ADD_CACHE_INFO(x, nr) do { swap_cache_info.x += (nr); } while (0)
68 unsigned long add_total
;
69 unsigned long del_total
;
70 unsigned long find_success
;
71 unsigned long find_total
;
74 unsigned long total_swapcache_pages(void)
76 unsigned int i
, j
, nr
;
77 unsigned long ret
= 0;
78 struct address_space
*spaces
;
81 for (i
= 0; i
< MAX_SWAPFILES
; i
++) {
83 * The corresponding entries in nr_swapper_spaces and
84 * swapper_spaces will be reused only after at least
85 * one grace period. So it is impossible for them
86 * belongs to different usage.
88 nr
= nr_swapper_spaces
[i
];
89 spaces
= rcu_dereference(swapper_spaces
[i
]);
92 for (j
= 0; j
< nr
; j
++)
93 ret
+= spaces
[j
].nrpages
;
99 static atomic_t swapin_readahead_hits
= ATOMIC_INIT(4);
101 void show_swap_cache_info(void)
103 printk("%lu pages in swap cache\n", total_swapcache_pages());
104 printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
105 swap_cache_info
.add_total
, swap_cache_info
.del_total
,
106 swap_cache_info
.find_success
, swap_cache_info
.find_total
);
107 printk("Free swap = %ldkB\n",
108 get_nr_swap_pages() << (PAGE_SHIFT
- 10));
109 printk("Total swap = %lukB\n", total_swap_pages
<< (PAGE_SHIFT
- 10));
113 * __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
114 * but sets SwapCache flag and private instead of mapping and index.
116 int __add_to_swap_cache(struct page
*page
, swp_entry_t entry
)
118 int error
, i
, nr
= hpage_nr_pages(page
);
119 struct address_space
*address_space
;
120 pgoff_t idx
= swp_offset(entry
);
122 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
123 VM_BUG_ON_PAGE(PageSwapCache(page
), page
);
124 VM_BUG_ON_PAGE(!PageSwapBacked(page
), page
);
126 page_ref_add(page
, nr
);
127 SetPageSwapCache(page
);
129 address_space
= swap_address_space(entry
);
130 spin_lock_irq(&address_space
->tree_lock
);
131 for (i
= 0; i
< nr
; i
++) {
132 set_page_private(page
+ i
, entry
.val
+ i
);
133 error
= radix_tree_insert(&address_space
->page_tree
,
138 if (likely(!error
)) {
139 address_space
->nrpages
+= nr
;
140 __mod_node_page_state(page_pgdat(page
), NR_FILE_PAGES
, nr
);
141 ADD_CACHE_INFO(add_total
, nr
);
144 * Only the context which have set SWAP_HAS_CACHE flag
145 * would call add_to_swap_cache().
146 * So add_to_swap_cache() doesn't returns -EEXIST.
148 VM_BUG_ON(error
== -EEXIST
);
149 set_page_private(page
+ i
, 0UL);
151 radix_tree_delete(&address_space
->page_tree
, idx
+ i
);
152 set_page_private(page
+ i
, 0UL);
154 ClearPageSwapCache(page
);
155 page_ref_sub(page
, nr
);
157 spin_unlock_irq(&address_space
->tree_lock
);
163 int add_to_swap_cache(struct page
*page
, swp_entry_t entry
, gfp_t gfp_mask
)
167 error
= radix_tree_maybe_preload_order(gfp_mask
, compound_order(page
));
169 error
= __add_to_swap_cache(page
, entry
);
170 radix_tree_preload_end();
176 * This must be called only on pages that have
177 * been verified to be in the swap cache.
179 void __delete_from_swap_cache(struct page
*page
)
181 struct address_space
*address_space
;
182 int i
, nr
= hpage_nr_pages(page
);
186 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
187 VM_BUG_ON_PAGE(!PageSwapCache(page
), page
);
188 VM_BUG_ON_PAGE(PageWriteback(page
), page
);
190 entry
.val
= page_private(page
);
191 address_space
= swap_address_space(entry
);
192 idx
= swp_offset(entry
);
193 for (i
= 0; i
< nr
; i
++) {
194 radix_tree_delete(&address_space
->page_tree
, idx
+ i
);
195 set_page_private(page
+ i
, 0);
197 ClearPageSwapCache(page
);
198 address_space
->nrpages
-= nr
;
199 __mod_node_page_state(page_pgdat(page
), NR_FILE_PAGES
, -nr
);
200 ADD_CACHE_INFO(del_total
, nr
);
204 * add_to_swap - allocate swap space for a page
205 * @page: page we want to move to swap
207 * Allocate swap space for the page and add the page to the
208 * swap cache. Caller needs to hold the page lock.
210 int add_to_swap(struct page
*page
)
215 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
216 VM_BUG_ON_PAGE(!PageUptodate(page
), page
);
218 entry
= get_swap_page(page
);
222 if (mem_cgroup_try_charge_swap(page
, entry
))
226 * Radix-tree node allocations from PF_MEMALLOC contexts could
227 * completely exhaust the page allocator. __GFP_NOMEMALLOC
228 * stops emergency reserves from being allocated.
230 * TODO: this could cause a theoretical memory reclaim
231 * deadlock in the swap out path.
234 * Add it to the swap cache.
236 err
= add_to_swap_cache(page
, entry
,
237 __GFP_HIGH
|__GFP_NOMEMALLOC
|__GFP_NOWARN
);
238 /* -ENOMEM radix-tree allocation failure */
241 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
242 * clear SWAP_HAS_CACHE flag.
246 * Normally the page will be dirtied in unmap because its pte should be
247 * dirty. A special case is MADV_FREE page. The page'e pte could have
248 * dirty bit cleared but the page's SwapBacked bit is still set because
249 * clearing the dirty bit and SwapBacked bit has no lock protected. For
250 * such page, unmap will not set dirty bit for it, so page reclaim will
251 * not write the page out. This can cause data corruption when the page
252 * is swap in later. Always setting the dirty bit for the page solves
255 set_page_dirty(page
);
260 put_swap_page(page
, entry
);
265 * This must be called only on pages that have
266 * been verified to be in the swap cache and locked.
267 * It will never put the page into the free list,
268 * the caller has a reference on the page.
270 void delete_from_swap_cache(struct page
*page
)
273 struct address_space
*address_space
;
275 entry
.val
= page_private(page
);
277 address_space
= swap_address_space(entry
);
278 spin_lock_irq(&address_space
->tree_lock
);
279 __delete_from_swap_cache(page
);
280 spin_unlock_irq(&address_space
->tree_lock
);
282 put_swap_page(page
, entry
);
283 page_ref_sub(page
, hpage_nr_pages(page
));
287 * If we are the only user, then try to free up the swap cache.
289 * Its ok to check for PageSwapCache without the page lock
290 * here because we are going to recheck again inside
291 * try_to_free_swap() _with_ the lock.
294 static inline void free_swap_cache(struct page
*page
)
296 if (PageSwapCache(page
) && !page_mapped(page
) && trylock_page(page
)) {
297 try_to_free_swap(page
);
303 * Perform a free_page(), also freeing any swap cache associated with
304 * this page if it is the last user of the page.
306 void free_page_and_swap_cache(struct page
*page
)
308 free_swap_cache(page
);
309 if (!is_huge_zero_page(page
))
314 * Passed an array of pages, drop them all from swapcache and then release
315 * them. They are removed from the LRU and freed if this is their last use.
317 void free_pages_and_swap_cache(struct page
**pages
, int nr
)
319 struct page
**pagep
= pages
;
323 for (i
= 0; i
< nr
; i
++)
324 free_swap_cache(pagep
[i
]);
325 release_pages(pagep
, nr
, false);
329 * Lookup a swap entry in the swap cache. A found page will be returned
330 * unlocked and with its refcount incremented - we rely on the kernel
331 * lock getting page table operations atomic even if we drop the page
332 * lock before returning.
334 struct page
*lookup_swap_cache(swp_entry_t entry
, struct vm_area_struct
*vma
,
338 unsigned long ra_info
;
339 int win
, hits
, readahead
;
341 page
= find_get_page(swap_address_space(entry
), swp_offset(entry
));
343 INC_CACHE_INFO(find_total
);
345 INC_CACHE_INFO(find_success
);
346 if (unlikely(PageTransCompound(page
)))
348 readahead
= TestClearPageReadahead(page
);
350 ra_info
= GET_SWAP_RA_VAL(vma
);
351 win
= SWAP_RA_WIN(ra_info
);
352 hits
= SWAP_RA_HITS(ra_info
);
354 hits
= min_t(int, hits
+ 1, SWAP_RA_HITS_MAX
);
355 atomic_long_set(&vma
->swap_readahead_info
,
356 SWAP_RA_VAL(addr
, win
, hits
));
359 count_vm_event(SWAP_RA_HIT
);
361 atomic_inc(&swapin_readahead_hits
);
367 struct page
*__read_swap_cache_async(swp_entry_t entry
, gfp_t gfp_mask
,
368 struct vm_area_struct
*vma
, unsigned long addr
,
369 bool *new_page_allocated
)
371 struct page
*found_page
, *new_page
= NULL
;
372 struct address_space
*swapper_space
= swap_address_space(entry
);
374 *new_page_allocated
= false;
378 * First check the swap cache. Since this is normally
379 * called after lookup_swap_cache() failed, re-calling
380 * that would confuse statistics.
382 found_page
= find_get_page(swapper_space
, swp_offset(entry
));
387 * Just skip read ahead for unused swap slot.
388 * During swap_off when swap_slot_cache is disabled,
389 * we have to handle the race between putting
390 * swap entry in swap cache and marking swap slot
391 * as SWAP_HAS_CACHE. That's done in later part of code or
392 * else swap_off will be aborted if we return NULL.
394 if (!__swp_swapcount(entry
) && swap_slot_cache_enabled
)
398 * Get a new page to read into from swap.
401 new_page
= alloc_page_vma(gfp_mask
, vma
, addr
);
403 break; /* Out of memory */
407 * call radix_tree_preload() while we can wait.
409 err
= radix_tree_maybe_preload(gfp_mask
& GFP_KERNEL
);
414 * Swap entry may have been freed since our caller observed it.
416 err
= swapcache_prepare(entry
);
417 if (err
== -EEXIST
) {
418 radix_tree_preload_end();
420 * We might race against get_swap_page() and stumble
421 * across a SWAP_HAS_CACHE swap_map entry whose page
422 * has not been brought into the swapcache yet.
427 if (err
) { /* swp entry is obsolete ? */
428 radix_tree_preload_end();
432 /* May fail (-ENOMEM) if radix-tree node allocation failed. */
433 __SetPageLocked(new_page
);
434 __SetPageSwapBacked(new_page
);
435 err
= __add_to_swap_cache(new_page
, entry
);
437 radix_tree_preload_end();
439 * Initiate read into locked page and return.
441 lru_cache_add_anon(new_page
);
442 *new_page_allocated
= true;
445 radix_tree_preload_end();
446 __ClearPageLocked(new_page
);
448 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
449 * clear SWAP_HAS_CACHE flag.
451 put_swap_page(new_page
, entry
);
452 } while (err
!= -ENOMEM
);
460 * Locate a page of swap in physical memory, reserving swap cache space
461 * and reading the disk if it is not already cached.
462 * A failure return means that either the page allocation failed or that
463 * the swap entry is no longer in use.
465 struct page
*read_swap_cache_async(swp_entry_t entry
, gfp_t gfp_mask
,
466 struct vm_area_struct
*vma
, unsigned long addr
, bool do_poll
)
468 bool page_was_allocated
;
469 struct page
*retpage
= __read_swap_cache_async(entry
, gfp_mask
,
470 vma
, addr
, &page_was_allocated
);
472 if (page_was_allocated
)
473 swap_readpage(retpage
, do_poll
);
478 static unsigned int __swapin_nr_pages(unsigned long prev_offset
,
479 unsigned long offset
,
484 unsigned int pages
, last_ra
;
487 * This heuristic has been found to work well on both sequential and
488 * random loads, swapping to hard disk or to SSD: please don't ask
489 * what the "+ 2" means, it just happens to work well, that's all.
494 * We can have no readahead hits to judge by: but must not get
495 * stuck here forever, so check for an adjacent offset instead
496 * (and don't even bother to check whether swap type is same).
498 if (offset
!= prev_offset
+ 1 && offset
!= prev_offset
- 1)
501 unsigned int roundup
= 4;
502 while (roundup
< pages
)
507 if (pages
> max_pages
)
510 /* Don't shrink readahead too fast */
511 last_ra
= prev_win
/ 2;
518 static unsigned long swapin_nr_pages(unsigned long offset
)
520 static unsigned long prev_offset
;
521 unsigned int hits
, pages
, max_pages
;
522 static atomic_t last_readahead_pages
;
524 max_pages
= 1 << READ_ONCE(page_cluster
);
528 hits
= atomic_xchg(&swapin_readahead_hits
, 0);
529 pages
= __swapin_nr_pages(prev_offset
, offset
, hits
, max_pages
,
530 atomic_read(&last_readahead_pages
));
532 prev_offset
= offset
;
533 atomic_set(&last_readahead_pages
, pages
);
539 * swapin_readahead - swap in pages in hope we need them soon
540 * @entry: swap entry of this memory
541 * @gfp_mask: memory allocation flags
542 * @vma: user vma this address belongs to
543 * @addr: target address for mempolicy
545 * Returns the struct page for entry and addr, after queueing swapin.
547 * Primitive swap readahead code. We simply read an aligned block of
548 * (1 << page_cluster) entries in the swap area. This method is chosen
549 * because it doesn't cost us any seek time. We also make sure to queue
550 * the 'original' request together with the readahead ones...
552 * This has been extended to use the NUMA policies from the mm triggering
555 * Caller must hold down_read on the vma->vm_mm if vma is not NULL.
557 struct page
*swapin_readahead(swp_entry_t entry
, gfp_t gfp_mask
,
558 struct vm_area_struct
*vma
, unsigned long addr
)
561 unsigned long entry_offset
= swp_offset(entry
);
562 unsigned long offset
= entry_offset
;
563 unsigned long start_offset
, end_offset
;
565 struct blk_plug plug
;
566 bool do_poll
= true, page_allocated
;
568 mask
= swapin_nr_pages(offset
) - 1;
573 /* Read a page_cluster sized and aligned cluster around offset. */
574 start_offset
= offset
& ~mask
;
575 end_offset
= offset
| mask
;
576 if (!start_offset
) /* First page is swap header. */
579 blk_start_plug(&plug
);
580 for (offset
= start_offset
; offset
<= end_offset
; offset
++) {
581 /* Ok, do the async read-ahead now */
582 page
= __read_swap_cache_async(
583 swp_entry(swp_type(entry
), offset
),
584 gfp_mask
, vma
, addr
, &page_allocated
);
587 if (page_allocated
) {
588 swap_readpage(page
, false);
589 if (offset
!= entry_offset
&&
590 likely(!PageTransCompound(page
))) {
591 SetPageReadahead(page
);
592 count_vm_event(SWAP_RA
);
597 blk_finish_plug(&plug
);
599 lru_add_drain(); /* Push any new pages onto the LRU now */
601 return read_swap_cache_async(entry
, gfp_mask
, vma
, addr
, do_poll
);
604 int init_swap_address_space(unsigned int type
, unsigned long nr_pages
)
606 struct address_space
*spaces
, *space
;
609 nr
= DIV_ROUND_UP(nr_pages
, SWAP_ADDRESS_SPACE_PAGES
);
610 spaces
= kvzalloc(sizeof(struct address_space
) * nr
, GFP_KERNEL
);
613 for (i
= 0; i
< nr
; i
++) {
615 INIT_RADIX_TREE(&space
->page_tree
, GFP_ATOMIC
|__GFP_NOWARN
);
616 atomic_set(&space
->i_mmap_writable
, 0);
617 space
->a_ops
= &swap_aops
;
618 /* swap cache doesn't use writeback related tags */
619 mapping_set_no_writeback_tags(space
);
620 spin_lock_init(&space
->tree_lock
);
622 nr_swapper_spaces
[type
] = nr
;
623 rcu_assign_pointer(swapper_spaces
[type
], spaces
);
628 void exit_swap_address_space(unsigned int type
)
630 struct address_space
*spaces
;
632 spaces
= swapper_spaces
[type
];
633 nr_swapper_spaces
[type
] = 0;
634 rcu_assign_pointer(swapper_spaces
[type
], NULL
);
639 static inline void swap_ra_clamp_pfn(struct vm_area_struct
*vma
,
643 unsigned long *start
,
646 *start
= max3(lpfn
, PFN_DOWN(vma
->vm_start
),
647 PFN_DOWN(faddr
& PMD_MASK
));
648 *end
= min3(rpfn
, PFN_DOWN(vma
->vm_end
),
649 PFN_DOWN((faddr
& PMD_MASK
) + PMD_SIZE
));
652 struct page
*swap_readahead_detect(struct vm_fault
*vmf
,
653 struct vma_swap_readahead
*swap_ra
)
655 struct vm_area_struct
*vma
= vmf
->vma
;
656 unsigned long swap_ra_info
;
659 unsigned long faddr
, pfn
, fpfn
;
660 unsigned long start
, end
;
662 unsigned int max_win
, hits
, prev_win
, win
, left
;
667 faddr
= vmf
->address
;
668 entry
= pte_to_swp_entry(vmf
->orig_pte
);
669 if ((unlikely(non_swap_entry(entry
))))
671 page
= lookup_swap_cache(entry
, vma
, faddr
);
675 max_win
= 1 << READ_ONCE(swap_ra_max_order
);
681 fpfn
= PFN_DOWN(faddr
);
682 swap_ra_info
= GET_SWAP_RA_VAL(vma
);
683 pfn
= PFN_DOWN(SWAP_RA_ADDR(swap_ra_info
));
684 prev_win
= SWAP_RA_WIN(swap_ra_info
);
685 hits
= SWAP_RA_HITS(swap_ra_info
);
686 swap_ra
->win
= win
= __swapin_nr_pages(pfn
, fpfn
, hits
,
688 atomic_long_set(&vma
->swap_readahead_info
,
689 SWAP_RA_VAL(faddr
, win
, 0));
694 /* Copy the PTEs because the page table may be unmapped */
696 swap_ra_clamp_pfn(vma
, faddr
, fpfn
, fpfn
+ win
, &start
, &end
);
697 else if (pfn
== fpfn
+ 1)
698 swap_ra_clamp_pfn(vma
, faddr
, fpfn
- win
+ 1, fpfn
+ 1,
701 left
= (win
- 1) / 2;
702 swap_ra_clamp_pfn(vma
, faddr
, fpfn
- left
, fpfn
+ win
- left
,
705 swap_ra
->nr_pte
= end
- start
;
706 swap_ra
->offset
= fpfn
- start
;
707 pte
= vmf
->pte
- swap_ra
->offset
;
711 tpte
= swap_ra
->ptes
;
712 for (pfn
= start
; pfn
!= end
; pfn
++)
719 struct page
*do_swap_page_readahead(swp_entry_t fentry
, gfp_t gfp_mask
,
720 struct vm_fault
*vmf
,
721 struct vma_swap_readahead
*swap_ra
)
723 struct blk_plug plug
;
724 struct vm_area_struct
*vma
= vmf
->vma
;
731 if (swap_ra
->win
== 1)
734 blk_start_plug(&plug
);
735 for (i
= 0, pte
= swap_ra
->ptes
; i
< swap_ra
->nr_pte
;
738 if (pte_none(pentry
))
740 if (pte_present(pentry
))
742 entry
= pte_to_swp_entry(pentry
);
743 if (unlikely(non_swap_entry(entry
)))
745 page
= __read_swap_cache_async(entry
, gfp_mask
, vma
,
746 vmf
->address
, &page_allocated
);
749 if (page_allocated
) {
750 swap_readpage(page
, false);
751 if (i
!= swap_ra
->offset
&&
752 likely(!PageTransCompound(page
))) {
753 SetPageReadahead(page
);
754 count_vm_event(SWAP_RA
);
759 blk_finish_plug(&plug
);
762 return read_swap_cache_async(fentry
, gfp_mask
, vma
, vmf
->address
,
767 static ssize_t
vma_ra_enabled_show(struct kobject
*kobj
,
768 struct kobj_attribute
*attr
, char *buf
)
770 return sprintf(buf
, "%s\n", swap_vma_readahead
? "true" : "false");
772 static ssize_t
vma_ra_enabled_store(struct kobject
*kobj
,
773 struct kobj_attribute
*attr
,
774 const char *buf
, size_t count
)
776 if (!strncmp(buf
, "true", 4) || !strncmp(buf
, "1", 1))
777 swap_vma_readahead
= true;
778 else if (!strncmp(buf
, "false", 5) || !strncmp(buf
, "0", 1))
779 swap_vma_readahead
= false;
785 static struct kobj_attribute vma_ra_enabled_attr
=
786 __ATTR(vma_ra_enabled
, 0644, vma_ra_enabled_show
,
787 vma_ra_enabled_store
);
789 static ssize_t
vma_ra_max_order_show(struct kobject
*kobj
,
790 struct kobj_attribute
*attr
, char *buf
)
792 return sprintf(buf
, "%d\n", swap_ra_max_order
);
794 static ssize_t
vma_ra_max_order_store(struct kobject
*kobj
,
795 struct kobj_attribute
*attr
,
796 const char *buf
, size_t count
)
800 err
= kstrtoint(buf
, 10, &v
);
801 if (err
|| v
> SWAP_RA_ORDER_CEILING
|| v
<= 0)
804 swap_ra_max_order
= v
;
808 static struct kobj_attribute vma_ra_max_order_attr
=
809 __ATTR(vma_ra_max_order
, 0644, vma_ra_max_order_show
,
810 vma_ra_max_order_store
);
812 static struct attribute
*swap_attrs
[] = {
813 &vma_ra_enabled_attr
.attr
,
814 &vma_ra_max_order_attr
.attr
,
818 static struct attribute_group swap_attr_group
= {
822 static int __init
swap_init_sysfs(void)
825 struct kobject
*swap_kobj
;
827 swap_kobj
= kobject_create_and_add("swap", mm_kobj
);
829 pr_err("failed to create swap kobject\n");
832 err
= sysfs_create_group(swap_kobj
, &swap_attr_group
);
834 pr_err("failed to register swap group\n");
840 kobject_put(swap_kobj
);
843 subsys_initcall(swap_init_sysfs
);