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swap: revert special hibernation allocation 

Please revert 2.6.36-rc commit d2997b1042
"hibernation: freeze swap at hibernation".  It complicated matters by
adding a second swap allocation path, just for hibernation; without in any
way fixing the issue that it was intended to address - page reclaim after
fixing the hibernation image might free swap from a page already imaged as
swapcache, letting its swap be reallocated to store a different page of
the image: resulting in data corruption if the imaged page were freed as
clean then swapped back in.  Pages freed to si->swap_map were still in
danger of being reallocated by the alternative allocation path.

I guess it inadvertently fixed slow SSD swap allocation for hibernation,
as reported by Nigel Cunningham: by missing out the discards that occur on
the usual swap allocation path; but that was unintentional, and needs a
separate fix.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Ondrej Zary <linux@rainbow-software.org>
Cc: Andrea Gelmini <andrea.gelmini@gmail.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Nigel Cunningham <nigel@tuxonice.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2010-09-09 16:38:07 -07:00 committed by Linus Torvalds
parent ac8456d6f9
commit 910321ea81
5 changed files with 26 additions and 84 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/swap.h
View File

@ -315,6 +315,7 @@ extern long nr_swap_pages;
extern long total_swap_pages;
extern void si_swapinfo(struct sysinfo *);
extern swp_entry_t get_swap_page(void);
extern swp_entry_t get_swap_page_of_type(int);
extern int valid_swaphandles(swp_entry_t, unsigned long *);
extern int add_swap_count_continuation(swp_entry_t, gfp_t);
extern void swap_shmem_alloc(swp_entry_t);
@ -331,13 +332,6 @@ extern int reuse_swap_page(struct page *);
extern int try_to_free_swap(struct page *);
struct backing_dev_info;
#ifdef CONFIG_HIBERNATION
void hibernation_freeze_swap(void);
void hibernation_thaw_swap(void);
swp_entry_t get_swap_for_hibernation(int type);
void swap_free_for_hibernation(swp_entry_t val);
#endif
/* linux/mm/thrash.c */
extern struct mm_struct *swap_token_mm;
extern void grab_swap_token(struct mm_struct *);

1
kernel/power/hibernate.c
View File

@ -338,7 +338,6 @@ int hibernation_snapshot(int platform_mode)
goto Close;
suspend_console();
hibernation_freeze_swap();
saved_mask = clear_gfp_allowed_mask(GFP_IOFS);
error = dpm_suspend_start(PMSG_FREEZE);
if (error)

1
kernel/power/snapshot.c
View File

@ -1086,7 +1086,6 @@ void swsusp_free(void)
buffer = NULL;
alloc_normal = 0;
alloc_highmem = 0;
hibernation_thaw_swap();
}
/* Helper functions used for the shrinking of memory. */

6
kernel/power/swap.c
View File

@ -136,10 +136,10 @@ sector_t alloc_swapdev_block(int swap)
{
unsigned long offset;
offset = swp_offset(get_swap_for_hibernation(swap));
offset = swp_offset(get_swap_page_of_type(swap));
if (offset) {
if (swsusp_extents_insert(offset))
swap_free_for_hibernation(swp_entry(swap, offset));
swap_free(swp_entry(swap, offset));
else
return swapdev_block(swap, offset);
}
@ -163,7 +163,7 @@ void free_all_swap_pages(int swap)
ext = container_of(node, struct swsusp_extent, node);
rb_erase(node, &swsusp_extents);
for (offset = ext->start; offset <= ext->end; offset++)
swap_free_for_hibernation(swp_entry(swap, offset));
swap_free(swp_entry(swap, offset));
kfree(ext);
}

94
mm/swapfile.c
View File

@ -47,8 +47,6 @@ 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 ";
@ -453,8 +451,6 @@ 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) {
@ -487,6 +483,28 @@ 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;
@ -746,74 +764,6 @@ 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).
*