Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc
[linux-2.6.git] / mm / swap_state.c
blobf24ab0dff554262e1da6866b866a4584871f8d9c
1 /*
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
8 */
9 #include <linux/mm.h>
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/page_cgroup.h>
22 #include <asm/pgtable.h>
25 * swapper_space is a fiction, retained to simplify the path through
26 * vmscan's shrink_page_list.
28 static const struct address_space_operations swap_aops = {
29 .writepage = swap_writepage,
30 .set_page_dirty = swap_set_page_dirty,
31 .migratepage = migrate_page,
34 static struct backing_dev_info swap_backing_dev_info = {
35 .name = "swap",
36 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
39 struct address_space swapper_spaces[MAX_SWAPFILES] = {
40 [0 ... MAX_SWAPFILES - 1] = {
41 .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN),
42 .a_ops = &swap_aops,
43 .backing_dev_info = &swap_backing_dev_info,
47 #define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0)
49 static struct {
50 unsigned long add_total;
51 unsigned long del_total;
52 unsigned long find_success;
53 unsigned long find_total;
54 } swap_cache_info;
56 unsigned long total_swapcache_pages(void)
58 int i;
59 unsigned long ret = 0;
61 for (i = 0; i < MAX_SWAPFILES; i++)
62 ret += swapper_spaces[i].nrpages;
63 return ret;
66 void show_swap_cache_info(void)
68 printk("%lu pages in swap cache\n", total_swapcache_pages());
69 printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
70 swap_cache_info.add_total, swap_cache_info.del_total,
71 swap_cache_info.find_success, swap_cache_info.find_total);
72 printk("Free swap = %ldkB\n",
73 get_nr_swap_pages() << (PAGE_SHIFT - 10));
74 printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
78 * __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
79 * but sets SwapCache flag and private instead of mapping and index.
81 int __add_to_swap_cache(struct page *page, swp_entry_t entry)
83 int error;
84 struct address_space *address_space;
86 VM_BUG_ON(!PageLocked(page));
87 VM_BUG_ON(PageSwapCache(page));
88 VM_BUG_ON(!PageSwapBacked(page));
90 page_cache_get(page);
91 SetPageSwapCache(page);
92 set_page_private(page, entry.val);
94 address_space = swap_address_space(entry);
95 spin_lock_irq(&address_space->tree_lock);
96 error = radix_tree_insert(&address_space->page_tree,
97 entry.val, page);
98 if (likely(!error)) {
99 address_space->nrpages++;
100 __inc_zone_page_state(page, NR_FILE_PAGES);
101 INC_CACHE_INFO(add_total);
103 spin_unlock_irq(&address_space->tree_lock);
105 if (unlikely(error)) {
107 * Only the context which have set SWAP_HAS_CACHE flag
108 * would call add_to_swap_cache().
109 * So add_to_swap_cache() doesn't returns -EEXIST.
111 VM_BUG_ON(error == -EEXIST);
112 set_page_private(page, 0UL);
113 ClearPageSwapCache(page);
114 page_cache_release(page);
117 return error;
121 int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
123 int error;
125 error = radix_tree_preload(gfp_mask);
126 if (!error) {
127 error = __add_to_swap_cache(page, entry);
128 radix_tree_preload_end();
130 return error;
134 * This must be called only on pages that have
135 * been verified to be in the swap cache.
137 void __delete_from_swap_cache(struct page *page)
139 swp_entry_t entry;
140 struct address_space *address_space;
142 VM_BUG_ON(!PageLocked(page));
143 VM_BUG_ON(!PageSwapCache(page));
144 VM_BUG_ON(PageWriteback(page));
146 entry.val = page_private(page);
147 address_space = swap_address_space(entry);
148 radix_tree_delete(&address_space->page_tree, page_private(page));
149 set_page_private(page, 0);
150 ClearPageSwapCache(page);
151 address_space->nrpages--;
152 __dec_zone_page_state(page, NR_FILE_PAGES);
153 INC_CACHE_INFO(del_total);
157 * add_to_swap - allocate swap space for a page
158 * @page: page we want to move to swap
160 * Allocate swap space for the page and add the page to the
161 * swap cache. Caller needs to hold the page lock.
163 int add_to_swap(struct page *page, struct list_head *list)
165 swp_entry_t entry;
166 int err;
168 VM_BUG_ON(!PageLocked(page));
169 VM_BUG_ON(!PageUptodate(page));
171 entry = get_swap_page();
172 if (!entry.val)
173 return 0;
175 if (unlikely(PageTransHuge(page)))
176 if (unlikely(split_huge_page_to_list(page, list))) {
177 swapcache_free(entry, NULL);
178 return 0;
182 * Radix-tree node allocations from PF_MEMALLOC contexts could
183 * completely exhaust the page allocator. __GFP_NOMEMALLOC
184 * stops emergency reserves from being allocated.
186 * TODO: this could cause a theoretical memory reclaim
187 * deadlock in the swap out path.
190 * Add it to the swap cache and mark it dirty
192 err = add_to_swap_cache(page, entry,
193 __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN);
195 if (!err) { /* Success */
196 SetPageDirty(page);
197 return 1;
198 } else { /* -ENOMEM radix-tree allocation failure */
200 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
201 * clear SWAP_HAS_CACHE flag.
203 swapcache_free(entry, NULL);
204 return 0;
209 * This must be called only on pages that have
210 * been verified to be in the swap cache and locked.
211 * It will never put the page into the free list,
212 * the caller has a reference on the page.
214 void delete_from_swap_cache(struct page *page)
216 swp_entry_t entry;
217 struct address_space *address_space;
219 entry.val = page_private(page);
221 address_space = swap_address_space(entry);
222 spin_lock_irq(&address_space->tree_lock);
223 __delete_from_swap_cache(page);
224 spin_unlock_irq(&address_space->tree_lock);
226 swapcache_free(entry, page);
227 page_cache_release(page);
231 * If we are the only user, then try to free up the swap cache.
233 * Its ok to check for PageSwapCache without the page lock
234 * here because we are going to recheck again inside
235 * try_to_free_swap() _with_ the lock.
236 * - Marcelo
238 static inline void free_swap_cache(struct page *page)
240 if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) {
241 try_to_free_swap(page);
242 unlock_page(page);
247 * Perform a free_page(), also freeing any swap cache associated with
248 * this page if it is the last user of the page.
250 void free_page_and_swap_cache(struct page *page)
252 free_swap_cache(page);
253 page_cache_release(page);
257 * Passed an array of pages, drop them all from swapcache and then release
258 * them. They are removed from the LRU and freed if this is their last use.
260 void free_pages_and_swap_cache(struct page **pages, int nr)
262 struct page **pagep = pages;
264 lru_add_drain();
265 while (nr) {
266 int todo = min(nr, PAGEVEC_SIZE);
267 int i;
269 for (i = 0; i < todo; i++)
270 free_swap_cache(pagep[i]);
271 release_pages(pagep, todo, 0);
272 pagep += todo;
273 nr -= todo;
278 * Lookup a swap entry in the swap cache. A found page will be returned
279 * unlocked and with its refcount incremented - we rely on the kernel
280 * lock getting page table operations atomic even if we drop the page
281 * lock before returning.
283 struct page * lookup_swap_cache(swp_entry_t entry)
285 struct page *page;
287 page = find_get_page(swap_address_space(entry), entry.val);
289 if (page)
290 INC_CACHE_INFO(find_success);
292 INC_CACHE_INFO(find_total);
293 return page;
297 * Locate a page of swap in physical memory, reserving swap cache space
298 * and reading the disk if it is not already cached.
299 * A failure return means that either the page allocation failed or that
300 * the swap entry is no longer in use.
302 struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
303 struct vm_area_struct *vma, unsigned long addr)
305 struct page *found_page, *new_page = NULL;
306 int err;
308 do {
310 * First check the swap cache. Since this is normally
311 * called after lookup_swap_cache() failed, re-calling
312 * that would confuse statistics.
314 found_page = find_get_page(swap_address_space(entry),
315 entry.val);
316 if (found_page)
317 break;
320 * Get a new page to read into from swap.
322 if (!new_page) {
323 new_page = alloc_page_vma(gfp_mask, vma, addr);
324 if (!new_page)
325 break; /* Out of memory */
329 * call radix_tree_preload() while we can wait.
331 err = radix_tree_preload(gfp_mask & GFP_KERNEL);
332 if (err)
333 break;
336 * Swap entry may have been freed since our caller observed it.
338 err = swapcache_prepare(entry);
339 if (err == -EEXIST) {
340 radix_tree_preload_end();
342 * We might race against get_swap_page() and stumble
343 * across a SWAP_HAS_CACHE swap_map entry whose page
344 * has not been brought into the swapcache yet, while
345 * the other end is scheduled away waiting on discard
346 * I/O completion at scan_swap_map().
348 * In order to avoid turning this transitory state
349 * into a permanent loop around this -EEXIST case
350 * if !CONFIG_PREEMPT and the I/O completion happens
351 * to be waiting on the CPU waitqueue where we are now
352 * busy looping, we just conditionally invoke the
353 * scheduler here, if there are some more important
354 * tasks to run.
356 cond_resched();
357 continue;
359 if (err) { /* swp entry is obsolete ? */
360 radix_tree_preload_end();
361 break;
364 /* May fail (-ENOMEM) if radix-tree node allocation failed. */
365 __set_page_locked(new_page);
366 SetPageSwapBacked(new_page);
367 err = __add_to_swap_cache(new_page, entry);
368 if (likely(!err)) {
369 radix_tree_preload_end();
371 * Initiate read into locked page and return.
373 lru_cache_add_anon(new_page);
374 swap_readpage(new_page);
375 return new_page;
377 radix_tree_preload_end();
378 ClearPageSwapBacked(new_page);
379 __clear_page_locked(new_page);
381 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
382 * clear SWAP_HAS_CACHE flag.
384 swapcache_free(entry, NULL);
385 } while (err != -ENOMEM);
387 if (new_page)
388 page_cache_release(new_page);
389 return found_page;
393 * swapin_readahead - swap in pages in hope we need them soon
394 * @entry: swap entry of this memory
395 * @gfp_mask: memory allocation flags
396 * @vma: user vma this address belongs to
397 * @addr: target address for mempolicy
399 * Returns the struct page for entry and addr, after queueing swapin.
401 * Primitive swap readahead code. We simply read an aligned block of
402 * (1 << page_cluster) entries in the swap area. This method is chosen
403 * because it doesn't cost us any seek time. We also make sure to queue
404 * the 'original' request together with the readahead ones...
406 * This has been extended to use the NUMA policies from the mm triggering
407 * the readahead.
409 * Caller must hold down_read on the vma->vm_mm if vma is not NULL.
411 struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
412 struct vm_area_struct *vma, unsigned long addr)
414 struct page *page;
415 unsigned long offset = swp_offset(entry);
416 unsigned long start_offset, end_offset;
417 unsigned long mask = (1UL << page_cluster) - 1;
418 struct blk_plug plug;
420 /* Read a page_cluster sized and aligned cluster around offset. */
421 start_offset = offset & ~mask;
422 end_offset = offset | mask;
423 if (!start_offset) /* First page is swap header. */
424 start_offset++;
426 blk_start_plug(&plug);
427 for (offset = start_offset; offset <= end_offset ; offset++) {
428 /* Ok, do the async read-ahead now */
429 page = read_swap_cache_async(swp_entry(swp_type(entry), offset),
430 gfp_mask, vma, addr);
431 if (!page)
432 continue;
433 page_cache_release(page);
435 blk_finish_plug(&plug);
437 lru_add_drain(); /* Push any new pages onto the LRU now */
438 return read_swap_cache_async(entry, gfp_mask, vma, addr);