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Subject[PATCH 4/4] swsusp: reduce the use of global variables
Date
The following patch reduces the use of global variables in the
snapshot-handling part of swsusp, snapshot.c.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

Index: linux-2.6.14-rc4-mm1/kernel/power/snapshot.c
===================================================================
--- linux-2.6.14-rc4-mm1.orig/kernel/power/snapshot.c 2005-10-17 23:28:40.000000000 +0200
+++ linux-2.6.14-rc4-mm1/kernel/power/snapshot.c 2005-10-18 00:13:02.000000000 +0200
@@ -164,37 +164,38 @@
return 1;
}

-static void count_data_pages(void)
+static unsigned count_data_pages(void)
{
struct zone *zone;
unsigned long zone_pfn;
+ unsigned n;

- nr_copy_pages = 0;
-
+ n = 0;
for_each_zone (zone) {
if (is_highmem(zone))
continue;
mark_free_pages(zone);
for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn)
- nr_copy_pages += saveable(zone, &zone_pfn);
+ n += saveable(zone, &zone_pfn);
}
+ return n;
}

-static void copy_data_pages(void)
+static void copy_data_pages(struct pbe *pblist)
{
struct zone *zone;
unsigned long zone_pfn;
- struct pbe *pbe = pagedir_nosave, *p;
+ struct pbe *pbe, *p;

- pr_debug("copy_data_pages(): pages to copy: %d\n", nr_copy_pages);
+ pbe = pblist;
for_each_zone (zone) {
if (is_highmem(zone))
continue;
mark_free_pages(zone);
/* This is necessary for swsusp_free() */
- for_each_pb_page (p, pagedir_nosave)
+ for_each_pb_page (p, pblist)
SetPageNosaveFree(virt_to_page(p));
- for_each_pbe (p, pagedir_nosave)
+ for_each_pbe (p, pblist)
SetPageNosaveFree(virt_to_page(p->address));
for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn) {
if (saveable(zone, &zone_pfn)) {
@@ -347,46 +348,39 @@
* free pages.
*/

-static int enough_free_mem(void)
+static int enough_free_mem(unsigned nr_pages)
{
pr_debug("swsusp: available memory: %u pages\n", nr_free_pages());
- return nr_free_pages() > (nr_copy_pages + PAGES_FOR_IO +
- nr_copy_pages/PBES_PER_PAGE + !!(nr_copy_pages%PBES_PER_PAGE));
+ return nr_free_pages() > (nr_pages + PAGES_FOR_IO +
+ (nr_pages + PBES_PER_PAGE - 1) / PBES_PER_PAGE);
}


-static int swsusp_alloc(void)
+static struct pbe *swsusp_alloc(unsigned nr_pages)
{
- struct pbe *p;
+ struct pbe *pblist, *p;

- pagedir_nosave = NULL;
-
- if (MAX_PBES < nr_copy_pages / PBES_PER_PAGE +
- !!(nr_copy_pages % PBES_PER_PAGE))
- return -ENOSPC;
-
- if (!(pagedir_save = alloc_pagedir(nr_copy_pages))) {
+ if (!(pblist = alloc_pagedir(nr_pages))) {
printk(KERN_ERR "suspend: Allocating pagedir failed.\n");
- return -ENOMEM;
+ return NULL;
}
- create_pbe_list(pagedir_save, nr_copy_pages);
- pagedir_nosave = pagedir_save;
+ create_pbe_list(pblist, nr_pages);

- for_each_pbe (p, pagedir_save) {
+ for_each_pbe (p, pblist) {
p->address = (unsigned long)alloc_image_page();
if (!p->address) {
printk(KERN_ERR "suspend: Allocating image pages failed.\n");
swsusp_free();
- return -ENOMEM;
+ return NULL;
}
}

- return 0;
+ return pblist;
}

int swsusp_save(void)
{
- int error;
+ unsigned nr_pages;

pr_debug("swsusp: critical section: \n");
if (save_highmem()) {
@@ -396,33 +390,37 @@
}

drain_local_pages();
- count_data_pages();
- printk("swsusp: Need to copy %u pages\n", nr_copy_pages);
+ nr_pages = count_data_pages();
+ printk("swsusp: Need to copy %u pages\n", nr_pages);

pr_debug("swsusp: pages needed: %u + %lu + %u, free: %u\n",
- nr_copy_pages,
- nr_copy_pages/PBES_PER_PAGE + !!(nr_copy_pages%PBES_PER_PAGE),
+ nr_pages,
+ (nr_pages + PBES_PER_PAGE - 1) / PBES_PER_PAGE,
PAGES_FOR_IO, nr_free_pages());

- if (!enough_free_mem()) {
+ /* This is needed because of the fixed size of swsusp_info */
+ if (MAX_PBES < (nr_pages + PBES_PER_PAGE - 1) / PBES_PER_PAGE)
+ return -ENOSPC;
+
+ if (!enough_free_mem(nr_pages)) {
printk(KERN_ERR "swsusp: Not enough free memory\n");
return -ENOMEM;
}

- if (!enough_swap()) {
+ if (!enough_swap(nr_pages)) {
printk(KERN_ERR "swsusp: Not enough free swap\n");
return -ENOSPC;
}

- error = swsusp_alloc();
- if (error)
- return error;
+ pagedir_nosave = swsusp_alloc(nr_pages);
+ if (!pagedir_nosave)
+ return -ENOMEM;

/* During allocating of suspend pagedir, new cold pages may appear.
* Kill them.
*/
drain_local_pages();
- copy_data_pages();
+ copy_data_pages(pagedir_nosave);

/*
* End of critical section. From now on, we can write to memory,
@@ -430,6 +428,8 @@
* touch swap space! Except we must write out our image of course.
*/

- printk("swsusp: critical section/: done (%d pages copied)\n", nr_copy_pages );
+ nr_copy_pages = nr_pages;
+
+ printk("swsusp: critical section/: done (%d pages copied)\n", nr_pages);
return 0;
}
Index: linux-2.6.14-rc4-mm1/kernel/power/swsusp.c
===================================================================
--- linux-2.6.14-rc4-mm1.orig/kernel/power/swsusp.c 2005-10-17 23:28:52.000000000 +0200
+++ linux-2.6.14-rc4-mm1/kernel/power/swsusp.c 2005-10-18 00:13:02.000000000 +0200
@@ -543,14 +543,14 @@
* We should only consider resume_device.
*/

-int enough_swap(void)
+int enough_swap(unsigned nr_pages)
{
struct sysinfo i;

si_swapinfo(&i);
pr_debug("swsusp: available swap: %lu pages\n", i.freeswap);
- return i.freeswap > (nr_copy_pages + PAGES_FOR_IO +
- nr_copy_pages/PBES_PER_PAGE + !!(nr_copy_pages%PBES_PER_PAGE));
+ return i.freeswap > (nr_pages + PAGES_FOR_IO +
+ (nr_pages + PBES_PER_PAGE - 1) / PBES_PER_PAGE);
}


Index: linux-2.6.14-rc4-mm1/kernel/power/power.h
===================================================================
--- linux-2.6.14-rc4-mm1.orig/kernel/power/power.h 2005-10-17 23:28:29.000000000 +0200
+++ linux-2.6.14-rc4-mm1/kernel/power/power.h 2005-10-18 00:13:02.000000000 +0200
@@ -69,4 +69,4 @@
extern struct pbe * alloc_pagedir(unsigned nr_pages);
extern void create_pbe_list(struct pbe *pblist, unsigned nr_pages);
extern void swsusp_free(void);
-extern int enough_swap(void);
+extern int enough_swap(unsigned nr_pages);
-
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