Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 | /*
* linux/mm/swap_state.c
*
* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
* Swap reorganised 29.12.95, Stephen Tweedie
*
* Rewritten to use page cache, (C) 1998 Stephen Tweedie
*/
#include <linux/mm.h>
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/swapctl.h>
#include <linux/init.h>
#include <linux/pagemap.h>
#include <linux/smp_lock.h>
#include <asm/pgtable.h>
struct address_space swapper_space = {
{ /* pages */
&swapper_space.pages, /* .next */
&swapper_space.pages /* .prev */
},
0 /* nrpages */
};
#ifdef SWAP_CACHE_INFO
unsigned long swap_cache_add_total = 0;
unsigned long swap_cache_del_total = 0;
unsigned long swap_cache_find_total = 0;
unsigned long swap_cache_find_success = 0;
void show_swap_cache_info(void)
{
printk("Swap cache: add %ld, delete %ld, find %ld/%ld\n",
swap_cache_add_total,
swap_cache_del_total,
swap_cache_find_success, swap_cache_find_total);
}
#endif
void add_to_swap_cache(struct page *page, swp_entry_t entry)
{
#ifdef SWAP_CACHE_INFO
swap_cache_add_total++;
#endif
if (PageTestandSetSwapCache(page))
BUG();
if (page->mapping)
BUG();
add_to_page_cache(page, &swapper_space, entry.val);
}
/*
* Verify that a swap entry is valid and increment its swap map count.
*
* Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
* "permanent", but will be reclaimed by the next swapoff.
*/
int swap_duplicate(swp_entry_t entry)
{
struct swap_info_struct * p;
unsigned long offset, type;
int result = 0;
/* Swap entry 0 is illegal */
if (!entry.val)
goto out;
type = SWP_TYPE(entry);
if (type >= nr_swapfiles)
goto bad_file;
p = type + swap_info;
offset = SWP_OFFSET(entry);
if (offset >= p->max)
goto bad_offset;
if (!p->swap_map[offset])
goto bad_unused;
/*
* Entry is valid, so increment the map count.
*/
if (p->swap_map[offset] < SWAP_MAP_MAX)
p->swap_map[offset]++;
else {
static int overflow = 0;
if (overflow++ < 5)
printk("VM: swap entry overflow\n");
p->swap_map[offset] = SWAP_MAP_MAX;
}
result = 1;
out:
return result;
bad_file:
printk("Bad swap file entry %08lx\n", entry.val);
goto out;
bad_offset:
printk("Bad swap offset entry %08lx\n", entry.val);
goto out;
bad_unused:
printk("Unused swap offset entry %08lx\n", entry.val);
goto out;
}
int swap_count(struct page *page)
{
struct swap_info_struct * p;
unsigned long offset, type;
swp_entry_t entry;
int retval = 0;
entry.val = page->index;
if (!entry.val)
goto bad_entry;
type = SWP_TYPE(entry);
if (type >= nr_swapfiles)
goto bad_file;
p = type + swap_info;
offset = SWP_OFFSET(entry);
if (offset >= p->max)
goto bad_offset;
if (!p->swap_map[offset])
goto bad_unused;
retval = p->swap_map[offset];
out:
return retval;
bad_entry:
printk(KERN_ERR "swap_count: null entry!\n");
goto out;
bad_file:
printk("Bad swap file entry %08lx\n", entry.val);
goto out;
bad_offset:
printk("Bad swap offset entry %08lx\n", entry.val);
goto out;
bad_unused:
printk("Unused swap offset entry %08lx\n", entry.val);
goto out;
}
static inline void remove_from_swap_cache(struct page *page)
{
struct address_space *mapping = page->mapping;
if (mapping != &swapper_space)
BUG();
if (!PageSwapCache(page))
PAGE_BUG(page);
PageClearSwapCache(page);
remove_inode_page(page);
}
/*
* This must be called only on pages that have
* been verified to be in the swap cache.
*/
void __delete_from_swap_cache(struct page *page)
{
swp_entry_t entry;
entry.val = page->index;
#ifdef SWAP_CACHE_INFO
swap_cache_del_total++;
#endif
remove_from_swap_cache(page);
lock_kernel();
swap_free(entry);
unlock_kernel();
}
static void delete_from_swap_cache_nolock(struct page *page)
{
if (block_flushpage(NULL, page, 0))
lru_cache_del(page);
__delete_from_swap_cache(page);
}
/*
* This must be called only on pages that have
* been verified to be in the swap cache.
*/
void delete_from_swap_cache(struct page *page)
{
lock_page(page);
delete_from_swap_cache_nolock(page);
UnlockPage(page);
page_cache_release(page);
}
/*
* Perform a free_page(), also freeing any swap cache associated with
* this page if it is the last user of the page.
*/
void free_page_and_swap_cache(struct page *page)
{
/*
* If we are the only user, then free up the swap cache.
*/
lock_page(page);
if (PageSwapCache(page) && !is_page_shared(page)) {
delete_from_swap_cache_nolock(page);
page_cache_release(page);
}
UnlockPage(page);
clear_bit(PG_swap_entry, &page->flags);
__free_page(page);
}
/*
* Lookup a swap entry in the swap cache. A found page will be returned
* unlocked and with its refcount incremented - we rely on the kernel
* lock getting page table operations atomic even if we drop the page
* lock before returning.
*/
struct page * lookup_swap_cache(swp_entry_t entry)
{
struct page *found;
#ifdef SWAP_CACHE_INFO
swap_cache_find_total++;
#endif
while (1) {
/*
* Right now the pagecache is 32-bit only. But it's a 32 bit index. =)
*/
found = find_lock_page(&swapper_space, entry.val);
if (!found)
return 0;
if (found->mapping != &swapper_space || !PageSwapCache(found))
goto out_bad;
#ifdef SWAP_CACHE_INFO
swap_cache_find_success++;
#endif
UnlockPage(found);
return found;
}
out_bad:
printk (KERN_ERR "VM: Found a non-swapper swap page!\n");
UnlockPage(found);
__free_page(found);
return 0;
}
/*
* Locate a page of swap in physical memory, reserving swap cache space
* and reading the disk if it is not already cached. If wait==0, we are
* only doing readahead, so don't worry if the page is already locked.
*
* A failure return means that either the page allocation failed or that
* the swap entry is no longer in use.
*/
struct page * read_swap_cache_async(swp_entry_t entry, int wait)
{
struct page *found_page = 0, *new_page;
unsigned long new_page_addr;
/*
* Make sure the swap entry is still in use.
*/
if (!swap_duplicate(entry)) /* Account for the swap cache */
goto out;
/*
* Look for the page in the swap cache.
*/
found_page = lookup_swap_cache(entry);
if (found_page)
goto out_free_swap;
new_page_addr = __get_free_page(GFP_USER);
if (!new_page_addr)
goto out_free_swap; /* Out of memory */
new_page = mem_map + MAP_NR(new_page_addr);
/*
* Check the swap cache again, in case we stalled above.
*/
found_page = lookup_swap_cache(entry);
if (found_page)
goto out_free_page;
/*
* Add it to the swap cache and read its contents.
*/
add_to_swap_cache(new_page, entry);
rw_swap_page(READ, new_page, wait);
return new_page;
out_free_page:
__free_page(new_page);
out_free_swap:
swap_free(entry);
out:
return found_page;
}
|