[PATCH] swsusp: rework memory freeing on resume

The following patch makes swsusp use the PG_nosave and PG_nosave_free flags to
mark pages that should be freed in case of an error during resume.

This allows us to simplify the code and to use swsusp_free() in all of the
swsusp's resume error paths, which makes them actually work.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 45 insertions, 83 deletions

diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index 761956e813f5..44ef5e799df0 100644
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -30,7 +30,6 @@ extern int swsusp_check(void);
 extern int swsusp_read(void);
 extern void swsusp_close(void);
 extern int swsusp_resume(void);
-extern int swsusp_free(void);
 
 
 static int noresume = 0;
@@ -252,14 +251,17 @@ static int software_resume(void)
 
         pr_debug("PM: Reading swsusp image.\n");
 
-        if ((error = swsusp_read()))
-                goto Cleanup;
+        if ((error = swsusp_read())) {
+                swsusp_free();
+                goto Thaw;
+        }
 
         pr_debug("PM: Preparing devices for restore.\n");
 
         if ((error = device_suspend(PMSG_FREEZE))) {
                 printk("Some devices failed to suspend\n");
-                goto Free;
+                swsusp_free();
+                goto Thaw;
         }
 
         mb();
@@ -268,9 +270,7 @@ static int software_resume(void)
         swsusp_resume();
         pr_debug("PM: Restore failed, recovering.n");
         device_resume();
- Free:
-        swsusp_free();
- Cleanup:
+ Thaw:
         unprepare_processes();
  Done:
         /* For success case, the suspend path will release the lock */
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 28afcb090149..d4fd96a135ab 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -66,7 +66,7 @@ extern asmlinkage int swsusp_arch_suspend(void);
 extern asmlinkage int swsusp_arch_resume(void);
 
 extern int restore_highmem(void);
-extern void free_pagedir(struct pbe *pblist);
 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(unsigned nr_pages);
diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 03916cf3ff02..84e686bdb40b 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -240,7 +240,7 @@ static void copy_data_pages(struct pbe *pblist)
  *      free_pagedir - free pages allocated with alloc_pagedir()
  */
 
-void free_pagedir(struct pbe *pblist)
+static void free_pagedir(struct pbe *pblist)
 {
         struct pbe *pbe;
 
diff --git a/kernel/power/swsusp.c b/kernel/power/swsusp.c
index f6abfdb0a02a..50667f4f3a2b 100644
--- a/kernel/power/swsusp.c
+++ b/kernel/power/swsusp.c
@@ -629,6 +629,11 @@ int swsusp_resume(void)
          * execution continues at place where swsusp_arch_suspend was called
          */
         BUG_ON(!error);
+        /* The only reason why swsusp_arch_resume() can fail is memory being
+         * very tight, so we have to free it as soon as we can to avoid
+         * subsequent failures
+         */
+        swsusp_free();
         restore_processor_state();
         restore_highmem();
         touch_softlockup_watchdog();
@@ -644,54 +649,28 @@ int swsusp_resume(void)
  *
  *      We don't know which pages are usable until we allocate them.
  *
- *      Allocated but unusable (ie eaten) memory pages are linked together
- *      to create a list, so that we can free them easily
- *
- *      We could have used a type other than (void *)
- *      for this purpose, but ...
+ *      Allocated but unusable (ie eaten) memory pages are marked so that
+ *      swsusp_free() can release them
  */
-static void **eaten_memory = NULL;
 
-static inline void eat_page(void *page)
-{
-        void **c;
-
-        c = eaten_memory;
-        eaten_memory = page;
-        *eaten_memory = c;
-}
-
-unsigned long get_usable_page(gfp_t gfp_mask)
+unsigned long get_safe_page(gfp_t gfp_mask)
 {
         unsigned long m;
 
-        m = get_zeroed_page(gfp_mask);
-        while (!PageNosaveFree(virt_to_page(m))) {
-                eat_page((void *)m);
+        do {
                 m = get_zeroed_page(gfp_mask);
-                if (!m)
-                        break;
+                if (m && PageNosaveFree(virt_to_page(m)))
+                        /* This is for swsusp_free() */
+                        SetPageNosave(virt_to_page(m));
+        } while (m && PageNosaveFree(virt_to_page(m)));
+        if (m) {
+                /* This is for swsusp_free() */
+                SetPageNosave(virt_to_page(m));
+                SetPageNosaveFree(virt_to_page(m));
         }
         return m;
 }
 
-void free_eaten_memory(void)
-{
-        unsigned long m;
-        void **c;
-        int i = 0;
-
-        c = eaten_memory;
-        while (c) {
-                m = (unsigned long)c;
-                c = *c;
-                free_page(m);
-                i++;
-        }
-        eaten_memory = NULL;
-        pr_debug("swsusp: %d unused pages freed\n", i);
-}
-
 /**
  *      check_pagedir - We ensure here that pages that the PBEs point to
  *      won't collide with pages where we're going to restore from the loaded
@@ -709,7 +688,7 @@ static int check_pagedir(struct pbe *pblist)
                 p->address = 0UL;
 
         for_each_pbe (p, pblist) {
-                p->address = get_usable_page(GFP_ATOMIC);
+                p->address = get_safe_page(GFP_ATOMIC);
                 if (!p->address)
                         return -ENOMEM;
         }
@@ -728,7 +707,7 @@ static struct pbe * swsusp_pagedir_relocate(struct pbe *pblist)
         unsigned long zone_pfn;
         struct pbe *pbpage, *tail, *p;
         void *m;
-        int rel = 0, error = 0;
+        int rel = 0;
 
         if (!pblist) /* a sanity check */
                 return NULL;
@@ -736,41 +715,37 @@ static struct pbe * swsusp_pagedir_relocate(struct pbe *pblist)
         pr_debug("swsusp: Relocating pagedir (%lu pages to check)\n",
                         swsusp_info.pagedir_pages);
 
-        /* Set page flags */
+        /* Clear page flags */
 
         for_each_zone (zone) {
                 for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn)
-                        SetPageNosaveFree(pfn_to_page(zone_pfn +
+                        if (pfn_valid(zone_pfn + zone->zone_start_pfn))
+                                ClearPageNosaveFree(pfn_to_page(zone_pfn +
                                         zone->zone_start_pfn));
         }
 
-        /* Clear orig addresses */
+        /* Mark orig addresses */
 
         for_each_pbe (p, pblist)
-                ClearPageNosaveFree(virt_to_page(p->orig_address));
+                SetPageNosaveFree(virt_to_page(p->orig_address));
 
         tail = pblist + PB_PAGE_SKIP;
 
         /* Relocate colliding pages */
 
         for_each_pb_page (pbpage, pblist) {
-                if (!PageNosaveFree(virt_to_page((unsigned long)pbpage))) {
-                        m = (void *)get_usable_page(GFP_ATOMIC | __GFP_COLD);
-                        if (!m) {
-                                error = -ENOMEM;
-                                break;
-                        }
+                if (PageNosaveFree(virt_to_page((unsigned long)pbpage))) {
+                        m = (void *)get_safe_page(GFP_ATOMIC | __GFP_COLD);
+                        if (!m)
+                                return NULL;
                         memcpy(m, (void *)pbpage, PAGE_SIZE);
                         if (pbpage == pblist)
                                 pblist = (struct pbe *)m;
                         else
                                 tail->next = (struct pbe *)m;
-
-                        eat_page((void *)pbpage);
                         pbpage = (struct pbe *)m;
 
                         /* We have to link the PBEs again */
-
                         for (p = pbpage; p < pbpage + PB_PAGE_SKIP; p++)
                                 if (p->next) /* needed to save the end */
                                         p->next = p + 1;
@@ -780,15 +755,13 @@ static struct pbe * swsusp_pagedir_relocate(struct pbe *pblist)
                 tail = pbpage + PB_PAGE_SKIP;
         }
 
-        if (error) {
-                printk("\nswsusp: Out of memory\n\n");
-                free_pagedir(pblist);
-                free_eaten_memory();
-                pblist = NULL;
-                /* Is this even worth handling? It should never ever happen, and we
-                   have just lost user's state, anyway... */
-        } else
-                printk("swsusp: Relocated %d pages\n", rel);
+        /* This is for swsusp_free() */
+        for_each_pb_page (pbpage, pblist) {
+                SetPageNosave(virt_to_page(pbpage));
+                SetPageNosaveFree(virt_to_page(pbpage));
+        }
+
+        printk("swsusp: Relocated %d pages\n", rel);
 
         return pblist;
 }
@@ -1006,9 +979,7 @@ static int read_pagedir(struct pbe *pblist)
                         break;
         }
 
-        if (error)
-                free_pagedir(pblist);
-        else
+        if (!error)
                 BUG_ON(i != swsusp_info.pagedir_pages);
 
         return error;
@@ -1051,15 +1022,6 @@ static int read_suspend_image(void)
         if (!error)
                 error = data_read(pagedir_nosave);
 
-        if (error) { /* We fail cleanly */
-                free_eaten_memory();
-                for_each_pbe (p, pagedir_nosave)
-                        if (p->address) {
-                                free_page(p->address);
-                                p->address = 0UL;
-                        }
-                free_pagedir(pagedir_nosave);
-        }
         return error;
 }