static int read_swapfiles(void) /* This is called before saving image */
{
int i, len;
len=strlen(resume_file);
root_swap = 0xFFFF;
swap_list_lock();
for(i=0; i<MAX_SWAPFILES; i++) {
if (swap_info[i].flags == 0) {
swapfile_used[i]=SWAPFILE_UNUSED;
} else {
if(!len) {
pr_debug("pmdisk: Default resume partition not set.\n");
if(root_swap == 0xFFFF) {
swapfile_used[i] = SWAPFILE_SUSPEND;
root_swap = i;
} else
swapfile_used[i] = SWAPFILE_IGNORED;
} else {
/* we ignore all swap devices that are not the resume_file */
if (1) {
// FIXME if(resume_device == swap_info[i].swap_device) {
swapfile_used[i] = SWAPFILE_SUSPEND;
root_swap = i;
} else
swapfile_used[i] = SWAPFILE_IGNORED;
}
}
}
swap_list_unlock();
return (root_swap != 0xffff) ? 0 : -ENODEV;
}
static int swsusp_swap_check(void) /* This is called before saving image */
{
int i, len;
len=strlen(resume_file);
root_swap = 0xFFFF;
swap_list_lock();
for(i=0; i<MAX_SWAPFILES; i++) {
if (swap_info[i].flags == 0) {
swapfile_used[i]=SWAPFILE_UNUSED;
} else {
if(!len) {
printk(KERN_WARNING "resume= option should be used to set suspend device" );
if(root_swap == 0xFFFF) {
swapfile_used[i] = SWAPFILE_SUSPEND;
root_swap = i;
} else
swapfile_used[i] = SWAPFILE_IGNORED;
} else {
/* we ignore all swap devices that are not the resume_file */
if (is_resume_device(&swap_info[i])) {
swapfile_used[i] = SWAPFILE_SUSPEND;
root_swap = i;
} else {
swapfile_used[i] = SWAPFILE_IGNORED;
}
}
}
}
swap_list_unlock();
return (root_swap != 0xffff) ? 0 : -ENODEV;
}
/**
* This is called after saving image so modification
* will be lost after resume... and that's what we want.
* we make the device unusable. A new call to
* lock_swapdevices can unlock the devices.
*/
static void lock_swapdevices(void)
{
int i;
swap_list_lock();
for(i = 0; i< MAX_SWAPFILES; i++)
if(swapfile_used[i] == SWAPFILE_IGNORED) {
swap_info[i].flags ^= 0xFF;
}
swap_list_unlock();
}
/* This is called after saving image so modification
will be lost after resume... and that's what we want. */
static void lock_swapdevices(void)
{
int i;
swap_list_lock();
for(i = 0; i< MAX_SWAPFILES; i++)
if(swapfile_used[i] == SWAPFILE_IGNORED) {
swap_info[i].flags ^= 0xFF; /* we make the device unusable. A new call to
lock_swapdevices can unlock the devices. */
}
swap_list_unlock();
}
static void lock_swapdevices(void) /* This is called after saving image so modification
will be lost after resume... and that's what we want. */
{
int i;
swap_list_lock();
for(i = 0; i< MAX_SWAPFILES; i++)
if(swapfile_used[i] == SWAPFILE_IGNORED) {
swap_info[i].flags ^= 0xFF; /* we make the device unusable. A new call to
lock_swapdevices can unlock the devices. */
}
swap_list_unlock();
}
swp_entry_t get_swap_page(void)
{
struct swap_info_struct * p;
unsigned long offset;
swp_entry_t entry;
int type, wrapped = 0;
entry.val = 0; /* Out of memory */
swap_list_lock();
type = swap_list.next;
if (type < 0)
goto out;
if (nr_swap_pages <= 0)
goto out;
while (1) {
p = &swap_info[type];
if ((p->flags & SWP_WRITEOK) == SWP_WRITEOK) {
swap_device_lock(p);
offset = scan_swap_map(p);
swap_device_unlock(p);
if (offset) {
entry = SWP_ENTRY(type,offset);
type = swap_info[type].next;
if (type < 0 ||
p->prio != swap_info[type].prio) {
swap_list.next = swap_list.head;
} else {
swap_list.next = type;
}
goto out;
}
}
type = p->next;
if (!wrapped) {
if (type < 0 || p->prio != swap_info[type].prio) {
type = swap_list.head;
wrapped = 1;
}
} else
if (type < 0)
goto out; /* out of swap space */
}
out:
swap_list_unlock();
return entry;
}
static void read_swapfiles(void) /* This is called before saving image */
{
int i, len;
len=strlen(resume_file);
root_swap = 0xFFFF;
swap_list_lock();
for(i=0; i<MAX_SWAPFILES; i++) {
if (swap_info[i].flags == 0) {
swapfile_used[i]=SWAPFILE_UNUSED;
} else {
if(!len) {
printk(KERN_WARNING "resume= option should be used to set suspend device" );
if(root_swap == 0xFFFF) {
swapfile_used[i] = SWAPFILE_SUSPEND;
root_swap = i;
} else
swapfile_used[i] = SWAPFILE_IGNORED;
} else {
/* we ignore all swap devices that are not the resume_file */
if (1) {
// FIXME if(resume_device == swap_info[i].swap_device) {
swapfile_used[i] = SWAPFILE_SUSPEND;
root_swap = i;
} else {
#if 0
printk( "Resume: device %s (%x != %x) ignored\n", swap_info[i].swap_file->d_name.name, swap_info[i].swap_device, resume_device );
#endif
swapfile_used[i] = SWAPFILE_IGNORED;
}
}
}
}
swap_list_unlock();
}
/*
* We completely avoid races by reading each swap page in advance,
* and then search for the process using it. All the necessary
* page table adjustments can then be made atomically.
*/
static int try_to_unuse(unsigned int type)
{
struct swap_info_struct * si = &swap_info[type];
struct mm_struct *start_mm;
unsigned short *swap_map;
unsigned short swcount;
struct page *page;
swp_entry_t entry;
int i = 0;
int retval = 0;
int reset_overflow = 0;
/*
* When searching mms for an entry, a good strategy is to
* start at the first mm we freed the previous entry from
* (though actually we don't notice whether we or coincidence
* freed the entry). Initialize this start_mm with a hold.
*
* A simpler strategy would be to start at the last mm we
* freed the previous entry from; but that would take less
* advantage of mmlist ordering (now preserved by swap_out()),
* which clusters forked address spaces together, most recent
* child immediately after parent. If we race with dup_mmap(),
* we very much want to resolve parent before child, otherwise
* we may miss some entries: using last mm would invert that.
*/
start_mm = &init_mm;
atomic_inc(&init_mm.mm_users);
/*
* Keep on scanning until all entries have gone. Usually,
* one pass through swap_map is enough, but not necessarily:
* mmput() removes mm from mmlist before exit_mmap() and its
* zap_page_range(). That's not too bad, those entries are
* on their way out, and handled faster there than here.
* do_munmap() behaves similarly, taking the range out of mm's
* vma list before zap_page_range(). But unfortunately, when
* unmapping a part of a vma, it takes the whole out first,
* then reinserts what's left after (might even reschedule if
* open() method called) - so swap entries may be invisible
* to swapoff for a while, then reappear - but that is rare.
*/
while ((i = find_next_to_unuse(si, i))) {
/*
* Get a page for the entry, using the existing swap
* cache page if there is one. Otherwise, get a clean
* page and read the swap into it.
*/
swap_map = &si->swap_map[i];
entry = SWP_ENTRY(type, i);
page = read_swap_cache_async(entry);
if (!page) {
/*
* Either swap_duplicate() failed because entry
* has been freed independently, and will not be
* reused since sys_swapoff() already disabled
* allocation from here, or alloc_page() failed.
*/
if (!*swap_map)
continue;
retval = -ENOMEM;
break;
}
/*
* Don't hold on to start_mm if it looks like exiting.
*/
if (atomic_read(&start_mm->mm_users) == 1) {
mmput(start_mm);
start_mm = &init_mm;
atomic_inc(&init_mm.mm_users);
}
/*
* Wait for and lock page. When do_swap_page races with
* try_to_unuse, do_swap_page can handle the fault much
* faster than try_to_unuse can locate the entry. This
* apparently redundant "wait_on_page" lets try_to_unuse
* defer to do_swap_page in such a case - in some tests,
* do_swap_page and try_to_unuse repeatedly compete.
*/
wait_on_page(page);
lock_page(page);
/*
* Remove all references to entry, without blocking.
* Whenever we reach init_mm, there's no address space
* to search, but use it as a reminder to search shmem.
*/
swcount = *swap_map;
if (swcount > 1) {
flush_page_to_ram(page);
if (start_mm == &init_mm)
shmem_unuse(entry, page);
else
unuse_process(start_mm, entry, page);
}
if (*swap_map > 1) {
int set_start_mm = (*swap_map >= swcount);
struct list_head *p = &start_mm->mmlist;
struct mm_struct *new_start_mm = start_mm;
struct mm_struct *mm;
spin_lock(&mmlist_lock);
while (*swap_map > 1 &&
(p = p->next) != &start_mm->mmlist) {
mm = list_entry(p, struct mm_struct, mmlist);
swcount = *swap_map;
if (mm == &init_mm) {
set_start_mm = 1;
shmem_unuse(entry, page);
} else
unuse_process(mm, entry, page);
if (set_start_mm && *swap_map < swcount) {
new_start_mm = mm;
set_start_mm = 0;
}
}
atomic_inc(&new_start_mm->mm_users);
spin_unlock(&mmlist_lock);
mmput(start_mm);
start_mm = new_start_mm;
}
/*
* How could swap count reach 0x7fff when the maximum
* pid is 0x7fff, and there's no way to repeat a swap
* page within an mm (except in shmem, where it's the
* shared object which takes the reference count)?
* We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
*
* If that's wrong, then we should worry more about
* exit_mmap() and do_munmap() cases described above:
* we might be resetting SWAP_MAP_MAX too early here.
* We know "Undead"s can happen, they're okay, so don't
* report them; but do report if we reset SWAP_MAP_MAX.
*/
if (*swap_map == SWAP_MAP_MAX) {
swap_list_lock();
swap_device_lock(si);
nr_swap_pages++;
*swap_map = 1;
swap_device_unlock(si);
swap_list_unlock();
reset_overflow = 1;
}
/*
* If a reference remains (rare), we would like to leave
* the page in the swap cache; but try_to_swap_out could
* then re-duplicate the entry once we drop page lock,
* so we might loop indefinitely; also, that page could
* not be swapped out to other storage meanwhile. So:
* delete from cache even if there's another reference,
* after ensuring that the data has been saved to disk -
* since if the reference remains (rarer), it will be
* read from disk into another page. Splitting into two
* pages would be incorrect if swap supported "shared
* private" pages, but they are handled by tmpfs files.
* Note shmem_unuse already deleted its from swap cache.
*/
if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
rw_swap_page(WRITE, page);
lock_page(page);
}
if (PageSwapCache(page))
delete_from_swap_cache(page);
/*
* So we could skip searching mms once swap count went
* to 1, we did not mark any present ptes as dirty: must
* mark page dirty so try_to_swap_out will preserve it.
*/
SetPageDirty(page);
UnlockPage(page);
page_cache_release(page);
/*
* Make sure that we aren't completely killing
* interactive performance. Interruptible check on
* signal_pending() would be nice, but changes the spec?
*/
if (current->need_resched)
schedule();
}
static void swap_info_put(struct swap_info_struct * p)
{
swap_device_unlock(p);
swap_list_unlock();
}
