sfc: Improve reliability of RX queue flushing
[linux-2.6/libata-dev.git] / mm / swap_state.c
blob42cd38eba79f1ffb096db8683bc11dd5604fe367
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/module.h>
10 #include <linux/mm.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/buffer_head.h>
17 #include <linux/backing-dev.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, to make sync_page look nicer, and to allow
27 * future use of radix_tree tags in the swap cache.
29 static const struct address_space_operations swap_aops = {
30 .writepage = swap_writepage,
31 .sync_page = block_sync_page,
32 .set_page_dirty = __set_page_dirty_nobuffers,
33 .migratepage = migrate_page,
36 static struct backing_dev_info swap_backing_dev_info = {
37 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
38 .unplug_io_fn = swap_unplug_io_fn,
41 struct address_space swapper_space = {
42 .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN),
43 .tree_lock = __SPIN_LOCK_UNLOCKED(swapper_space.tree_lock),
44 .a_ops = &swap_aops,
45 .i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear),
46 .backing_dev_info = &swap_backing_dev_info,
49 #define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0)
51 static struct {
52 unsigned long add_total;
53 unsigned long del_total;
54 unsigned long find_success;
55 unsigned long find_total;
56 } swap_cache_info;
58 void show_swap_cache_info(void)
60 printk("%lu pages in swap cache\n", total_swapcache_pages);
61 printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
62 swap_cache_info.add_total, swap_cache_info.del_total,
63 swap_cache_info.find_success, swap_cache_info.find_total);
64 printk("Free swap = %ldkB\n", nr_swap_pages << (PAGE_SHIFT - 10));
65 printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
69 * add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
70 * but sets SwapCache flag and private instead of mapping and index.
72 int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
74 int error;
76 VM_BUG_ON(!PageLocked(page));
77 VM_BUG_ON(PageSwapCache(page));
78 VM_BUG_ON(!PageSwapBacked(page));
80 error = radix_tree_preload(gfp_mask);
81 if (!error) {
82 page_cache_get(page);
83 SetPageSwapCache(page);
84 set_page_private(page, entry.val);
86 spin_lock_irq(&swapper_space.tree_lock);
87 error = radix_tree_insert(&swapper_space.page_tree,
88 entry.val, page);
89 if (likely(!error)) {
90 total_swapcache_pages++;
91 __inc_zone_page_state(page, NR_FILE_PAGES);
92 INC_CACHE_INFO(add_total);
94 spin_unlock_irq(&swapper_space.tree_lock);
95 radix_tree_preload_end();
97 if (unlikely(error)) {
98 set_page_private(page, 0UL);
99 ClearPageSwapCache(page);
100 page_cache_release(page);
103 return error;
107 * This must be called only on pages that have
108 * been verified to be in the swap cache.
110 void __delete_from_swap_cache(struct page *page)
112 VM_BUG_ON(!PageLocked(page));
113 VM_BUG_ON(!PageSwapCache(page));
114 VM_BUG_ON(PageWriteback(page));
116 radix_tree_delete(&swapper_space.page_tree, page_private(page));
117 set_page_private(page, 0);
118 ClearPageSwapCache(page);
119 total_swapcache_pages--;
120 __dec_zone_page_state(page, NR_FILE_PAGES);
121 INC_CACHE_INFO(del_total);
125 * add_to_swap - allocate swap space for a page
126 * @page: page we want to move to swap
128 * Allocate swap space for the page and add the page to the
129 * swap cache. Caller needs to hold the page lock.
131 int add_to_swap(struct page *page)
133 swp_entry_t entry;
134 int err;
136 VM_BUG_ON(!PageLocked(page));
137 VM_BUG_ON(!PageUptodate(page));
139 for (;;) {
140 entry = get_swap_page();
141 if (!entry.val)
142 return 0;
145 * Radix-tree node allocations from PF_MEMALLOC contexts could
146 * completely exhaust the page allocator. __GFP_NOMEMALLOC
147 * stops emergency reserves from being allocated.
149 * TODO: this could cause a theoretical memory reclaim
150 * deadlock in the swap out path.
153 * Add it to the swap cache and mark it dirty
155 err = add_to_swap_cache(page, entry,
156 __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN);
158 switch (err) {
159 case 0: /* Success */
160 SetPageDirty(page);
161 return 1;
162 case -EEXIST:
163 /* Raced with "speculative" read_swap_cache_async */
164 swapcache_free(entry, NULL);
165 continue;
166 default:
167 /* -ENOMEM radix-tree allocation failure */
168 swapcache_free(entry, NULL);
169 return 0;
175 * This must be called only on pages that have
176 * been verified to be in the swap cache and locked.
177 * It will never put the page into the free list,
178 * the caller has a reference on the page.
180 void delete_from_swap_cache(struct page *page)
182 swp_entry_t entry;
184 entry.val = page_private(page);
186 spin_lock_irq(&swapper_space.tree_lock);
187 __delete_from_swap_cache(page);
188 spin_unlock_irq(&swapper_space.tree_lock);
190 swapcache_free(entry, page);
191 page_cache_release(page);
195 * If we are the only user, then try to free up the swap cache.
197 * Its ok to check for PageSwapCache without the page lock
198 * here because we are going to recheck again inside
199 * try_to_free_swap() _with_ the lock.
200 * - Marcelo
202 static inline void free_swap_cache(struct page *page)
204 if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) {
205 try_to_free_swap(page);
206 unlock_page(page);
211 * Perform a free_page(), also freeing any swap cache associated with
212 * this page if it is the last user of the page.
214 void free_page_and_swap_cache(struct page *page)
216 free_swap_cache(page);
217 page_cache_release(page);
221 * Passed an array of pages, drop them all from swapcache and then release
222 * them. They are removed from the LRU and freed if this is their last use.
224 void free_pages_and_swap_cache(struct page **pages, int nr)
226 struct page **pagep = pages;
228 lru_add_drain();
229 while (nr) {
230 int todo = min(nr, PAGEVEC_SIZE);
231 int i;
233 for (i = 0; i < todo; i++)
234 free_swap_cache(pagep[i]);
235 release_pages(pagep, todo, 0);
236 pagep += todo;
237 nr -= todo;
242 * Lookup a swap entry in the swap cache. A found page will be returned
243 * unlocked and with its refcount incremented - we rely on the kernel
244 * lock getting page table operations atomic even if we drop the page
245 * lock before returning.
247 struct page * lookup_swap_cache(swp_entry_t entry)
249 struct page *page;
251 page = find_get_page(&swapper_space, entry.val);
253 if (page)
254 INC_CACHE_INFO(find_success);
256 INC_CACHE_INFO(find_total);
257 return page;
261 * Locate a page of swap in physical memory, reserving swap cache space
262 * and reading the disk if it is not already cached.
263 * A failure return means that either the page allocation failed or that
264 * the swap entry is no longer in use.
266 struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
267 struct vm_area_struct *vma, unsigned long addr)
269 struct page *found_page, *new_page = NULL;
270 int err;
272 do {
274 * First check the swap cache. Since this is normally
275 * called after lookup_swap_cache() failed, re-calling
276 * that would confuse statistics.
278 found_page = find_get_page(&swapper_space, entry.val);
279 if (found_page)
280 break;
283 * Get a new page to read into from swap.
285 if (!new_page) {
286 new_page = alloc_page_vma(gfp_mask, vma, addr);
287 if (!new_page)
288 break; /* Out of memory */
292 * Swap entry may have been freed since our caller observed it.
294 err = swapcache_prepare(entry);
295 if (err == -EEXIST) /* seems racy */
296 continue;
297 if (err) /* swp entry is obsolete ? */
298 break;
301 * Associate the page with swap entry in the swap cache.
302 * May fail (-EEXIST) if there is already a page associated
303 * with this entry in the swap cache: added by a racing
304 * read_swap_cache_async, or add_to_swap or shmem_writepage
305 * re-using the just freed swap entry for an existing page.
306 * May fail (-ENOMEM) if radix-tree node allocation failed.
308 __set_page_locked(new_page);
309 SetPageSwapBacked(new_page);
310 err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL);
311 if (likely(!err)) {
313 * Initiate read into locked page and return.
315 lru_cache_add_anon(new_page);
316 swap_readpage(new_page);
317 return new_page;
319 ClearPageSwapBacked(new_page);
320 __clear_page_locked(new_page);
321 swapcache_free(entry, NULL);
322 } while (err != -ENOMEM);
324 if (new_page)
325 page_cache_release(new_page);
326 return found_page;
330 * swapin_readahead - swap in pages in hope we need them soon
331 * @entry: swap entry of this memory
332 * @gfp_mask: memory allocation flags
333 * @vma: user vma this address belongs to
334 * @addr: target address for mempolicy
336 * Returns the struct page for entry and addr, after queueing swapin.
338 * Primitive swap readahead code. We simply read an aligned block of
339 * (1 << page_cluster) entries in the swap area. This method is chosen
340 * because it doesn't cost us any seek time. We also make sure to queue
341 * the 'original' request together with the readahead ones...
343 * This has been extended to use the NUMA policies from the mm triggering
344 * the readahead.
346 * Caller must hold down_read on the vma->vm_mm if vma is not NULL.
348 struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
349 struct vm_area_struct *vma, unsigned long addr)
351 int nr_pages;
352 struct page *page;
353 unsigned long offset;
354 unsigned long end_offset;
357 * Get starting offset for readaround, and number of pages to read.
358 * Adjust starting address by readbehind (for NUMA interleave case)?
359 * No, it's very unlikely that swap layout would follow vma layout,
360 * more likely that neighbouring swap pages came from the same node:
361 * so use the same "addr" to choose the same node for each swap read.
363 nr_pages = valid_swaphandles(entry, &offset);
364 for (end_offset = offset + nr_pages; offset < end_offset; offset++) {
365 /* Ok, do the async read-ahead now */
366 page = read_swap_cache_async(swp_entry(swp_type(entry), offset),
367 gfp_mask, vma, addr);
368 if (!page)
369 break;
370 page_cache_release(page);
372 lru_add_drain(); /* Push any new pages onto the LRU now */
373 return read_swap_cache_async(entry, gfp_mask, vma, addr);