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hibernation: freeze swap at hibernation

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When taking a memory snapshot in hibernate_snapshot(), all (directly
called) memory allocations use GFP_ATOMIC.  Hence swap misusage during
hibernation never occurs.

But from a pessimistic point of view, there is no guarantee that no page
allcation has __GFP_WAIT.  It is better to have a global indication "we
enter hibernation, don't use swap!".

This patch tries to freeze new-swap-allocation during hibernation.  (All
user processes are frozenm so swapin is not a concern).

This way, no updates will happen to swap_map[] between
hibernate_snapshot() and save_image().  Swap is thawed when swsusp_free()
is called.  We can be assured that swap corruption will not occur.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Hugh Dickins <hughd@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Ondrej Zary <linux@rainbow-software.org>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KAMEZAWA Hiroyuki
2010-08-09 17:20:11 -07:00
committed by Linus Torvalds
parent 966cca029f
commit d2997b1042
5 changed files with 84 additions and 26 deletions
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94
mm/swapfile.c
View File

@ -47,6 +47,8 @@ long nr_swap_pages;
long total_swap_pages;
static int least_priority;
static bool swap_for_hibernation;
static const char Bad_file[] = "Bad swap file entry ";
static const char Unused_file[] = "Unused swap file entry ";
static const char Bad_offset[] = "Bad swap offset entry ";
@ -451,6 +453,8 @@ swp_entry_t get_swap_page(void)
spin_lock(&swap_lock);
if (nr_swap_pages <= 0)
goto noswap;
if (swap_for_hibernation)
goto noswap;
nr_swap_pages--;
for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
@ -483,28 +487,6 @@ noswap:
return (swp_entry_t) {0};
}
/* The only caller of this function is now susupend routine */
swp_entry_t get_swap_page_of_type(int type)
{
struct swap_info_struct *si;
pgoff_t offset;
spin_lock(&swap_lock);
si = swap_info[type];
if (si && (si->flags & SWP_WRITEOK)) {
nr_swap_pages--;
/* This is called for allocating swap entry, not cache */
offset = scan_swap_map(si, 1);
if (offset) {
spin_unlock(&swap_lock);
return swp_entry(type, offset);
}
nr_swap_pages++;
}
spin_unlock(&swap_lock);
return (swp_entry_t) {0};
}
static struct swap_info_struct *swap_info_get(swp_entry_t entry)
{
struct swap_info_struct *p;
@ -764,6 +746,74 @@ int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep)
#endif
#ifdef CONFIG_HIBERNATION
static pgoff_t hibernation_offset[MAX_SWAPFILES];
/*
* Once hibernation starts to use swap, we freeze swap_map[]. Otherwise,
* saved swap_map[] image to the disk will be an incomplete because it's
* changing without synchronization with hibernation snap shot.
* At resume, we just make swap_for_hibernation=false. We can forget
* used maps easily.
*/
void hibernation_freeze_swap(void)
{
int i;
spin_lock(&swap_lock);
printk(KERN_INFO "PM: Freeze Swap\n");
swap_for_hibernation = true;
for (i = 0; i < MAX_SWAPFILES; i++)
hibernation_offset[i] = 1;
spin_unlock(&swap_lock);
}
void hibernation_thaw_swap(void)
{
spin_lock(&swap_lock);
if (swap_for_hibernation) {
printk(KERN_INFO "PM: Thaw Swap\n");
swap_for_hibernation = false;
}
spin_unlock(&swap_lock);
}
/*
* Because updateing swap_map[] can make not-saved-status-change,
* we use our own easy allocator.
* Please see kernel/power/swap.c, Used swaps are recorded into
* RB-tree.
*/
swp_entry_t get_swap_for_hibernation(int type)
{
pgoff_t off;
swp_entry_t val = {0};
struct swap_info_struct *si;
spin_lock(&swap_lock);
si = swap_info[type];
if (!si || !(si->flags & SWP_WRITEOK))
goto done;
for (off = hibernation_offset[type]; off < si->max; ++off) {
if (!si->swap_map[off])
break;
}
if (off < si->max) {
val = swp_entry(type, off);
hibernation_offset[type] = off + 1;
}
done:
spin_unlock(&swap_lock);
return val;
}
void swap_free_for_hibernation(swp_entry_t ent)
{
/* Nothing to do */
}
/*
* Find the swap type that corresponds to given device (if any).
*