]> Pileus Git - ~andy/linux/blobdiff - kernel/power/snapshot.c
[PATCH] Change the name of pagedir_nosave
[~andy/linux] / kernel / power / snapshot.c
index 8d5a5986d6213919e991835d8a4fcc7ecaaf018d..1d276b3ae15292df2e92c64de9069c8a13975b14 100644 (file)
@@ -10,6 +10,7 @@
  */
 
 
+#include <linux/version.h>
 #include <linux/module.h>
 #include <linux/mm.h>
 #include <linux/suspend.h>
 
 #include "power.h"
 
-struct pbe *pagedir_nosave;
-unsigned int nr_copy_pages;
+/* List of PBEs used for creating and restoring the suspend image */
+struct pbe *restore_pblist;
+
+static unsigned int nr_copy_pages;
+static unsigned int nr_meta_pages;
+static unsigned long *buffer;
 
 #ifdef CONFIG_HIGHMEM
 unsigned int count_highmem_pages(void)
@@ -80,7 +85,7 @@ static int save_highmem_zone(struct zone *zone)
                void *kaddr;
                unsigned long pfn = zone_pfn + zone->zone_start_pfn;
 
-               if (!(pfn%1000))
+               if (!(pfn%10000))
                        printk(".");
                if (!pfn_valid(pfn))
                        continue;
@@ -119,13 +124,15 @@ int save_highmem(void)
        struct zone *zone;
        int res = 0;
 
-       pr_debug("swsusp: Saving Highmem\n");
+       pr_debug("swsusp: Saving Highmem");
+       drain_local_pages();
        for_each_zone (zone) {
                if (is_highmem(zone))
                        res = save_highmem_zone(zone);
                if (res)
                        return res;
        }
+       printk("\n");
        return 0;
 }
 
@@ -145,9 +152,65 @@ int restore_highmem(void)
        }
        return 0;
 }
+#else
+static inline unsigned int count_highmem_pages(void) {return 0;}
+static inline int save_highmem(void) {return 0;}
+static inline int restore_highmem(void) {return 0;}
 #endif
 
-static int pfn_is_nosave(unsigned long pfn)
+/**
+ *     @safe_needed - on resume, for storing the PBE list and the image,
+ *     we can only use memory pages that do not conflict with the pages
+ *     used before suspend.
+ *
+ *     The unsafe pages are marked with the PG_nosave_free flag
+ *     and we count them using unsafe_pages
+ */
+
+static unsigned int unsafe_pages;
+
+static void *alloc_image_page(gfp_t gfp_mask, int safe_needed)
+{
+       void *res;
+
+       res = (void *)get_zeroed_page(gfp_mask);
+       if (safe_needed)
+               while (res && PageNosaveFree(virt_to_page(res))) {
+                       /* The page is unsafe, mark it for swsusp_free() */
+                       SetPageNosave(virt_to_page(res));
+                       unsafe_pages++;
+                       res = (void *)get_zeroed_page(gfp_mask);
+               }
+       if (res) {
+               SetPageNosave(virt_to_page(res));
+               SetPageNosaveFree(virt_to_page(res));
+       }
+       return res;
+}
+
+unsigned long get_safe_page(gfp_t gfp_mask)
+{
+       return (unsigned long)alloc_image_page(gfp_mask, 1);
+}
+
+/**
+ *     free_image_page - free page represented by @addr, allocated with
+ *     alloc_image_page (page flags set by it must be cleared)
+ */
+
+static inline void free_image_page(void *addr, int clear_nosave_free)
+{
+       ClearPageNosave(virt_to_page(addr));
+       if (clear_nosave_free)
+               ClearPageNosaveFree(virt_to_page(addr));
+       free_page((unsigned long)addr);
+}
+
+/**
+ *     pfn_is_nosave - check if given pfn is in the 'nosave' section
+ */
+
+static inline int pfn_is_nosave(unsigned long pfn)
 {
        unsigned long nosave_begin_pfn = __pa(&__nosave_begin) >> PAGE_SHIFT;
        unsigned long nosave_end_pfn = PAGE_ALIGN(__pa(&__nosave_end)) >> PAGE_SHIFT;
@@ -158,71 +221,77 @@ static int pfn_is_nosave(unsigned long pfn)
  *     saveable - Determine whether a page should be cloned or not.
  *     @pfn:   The page
  *
- *     We save a page if it's Reserved, and not in the range of pages
- *     statically defined as 'unsaveable', or if it isn't reserved, and
- *     isn't part of a free chunk of pages.
+ *     We save a page if it isn't Nosave, and is not in the range of pages
+ *     statically defined as 'unsaveable', and it
+ *     isn't part of a free chunk of pages.
  */
 
-static int saveable(struct zone *zone, unsigned long *zone_pfn)
+static struct page *saveable_page(unsigned long pfn)
 {
-       unsigned long pfn = *zone_pfn + zone->zone_start_pfn;
        struct page *page;
 
        if (!pfn_valid(pfn))
-               return 0;
+               return NULL;
 
        page = pfn_to_page(pfn);
-       BUG_ON(PageReserved(page) && PageNosave(page));
+
        if (PageNosave(page))
-               return 0;
+               return NULL;
        if (PageReserved(page) && pfn_is_nosave(pfn))
-               return 0;
+               return NULL;
        if (PageNosaveFree(page))
-               return 0;
+               return NULL;
 
-       return 1;
+       return page;
 }
 
 unsigned int count_data_pages(void)
 {
        struct zone *zone;
-       unsigned long zone_pfn;
+       unsigned long pfn, max_zone_pfn;
        unsigned int 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)
-                       n += saveable(zone, &zone_pfn);
+               max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
+               for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
+                       n += !!saveable_page(pfn);
        }
        return n;
 }
 
+static inline void copy_data_page(long *dst, long *src)
+{
+       int n;
+
+       /* copy_page and memcpy are not usable for copying task structs. */
+       for (n = PAGE_SIZE / sizeof(long); n; n--)
+               *dst++ = *src++;
+}
+
 static void copy_data_pages(struct pbe *pblist)
 {
        struct zone *zone;
-       unsigned long zone_pfn;
-       struct pbe *pbe, *p;
+       unsigned long pfn, max_zone_pfn;
+       struct pbe *pbe;
 
        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, pblist)
-                       SetPageNosaveFree(virt_to_page(p));
-               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)) {
-                               struct page *page;
-                               page = pfn_to_page(zone_pfn + zone->zone_start_pfn);
+               max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
+               for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
+                       struct page *page = saveable_page(pfn);
+
+                       if (page) {
+                               void *ptr = page_address(page);
+
                                BUG_ON(!pbe);
-                               pbe->orig_address = (unsigned long)page_address(page);
-                               /* copy_page is not usable for copying task structs. */
-                               memcpy((void *)pbe->address, (void *)pbe->orig_address, PAGE_SIZE);
+                               copy_data_page((void *)pbe->address, ptr);
+                               pbe->orig_address = (unsigned long)ptr;
                                pbe = pbe->next;
                        }
                }
@@ -230,20 +299,17 @@ static void copy_data_pages(struct pbe *pblist)
        BUG_ON(pbe);
 }
 
-
 /**
  *     free_pagedir - free pages allocated with alloc_pagedir()
  */
 
-void free_pagedir(struct pbe *pblist)
+static void free_pagedir(struct pbe *pblist, int clear_nosave_free)
 {
        struct pbe *pbe;
 
        while (pblist) {
                pbe = (pblist + PB_PAGE_SKIP)->next;
-               ClearPageNosave(virt_to_page(pblist));
-               ClearPageNosaveFree(virt_to_page(pblist));
-               free_page((unsigned long)pblist);
+               free_image_page(pblist, clear_nosave_free);
                pblist = pbe;
        }
 }
@@ -252,12 +318,12 @@ void free_pagedir(struct pbe *pblist)
  *     fill_pb_page - Create a list of PBEs on a given memory page
  */
 
-static inline void fill_pb_page(struct pbe *pbpage)
+static inline void fill_pb_page(struct pbe *pbpage, unsigned int n)
 {
        struct pbe *p;
 
        p = pbpage;
-       pbpage += PB_PAGE_SKIP;
+       pbpage += n - 1;
        do
                p->next = p + 1;
        while (++p < pbpage);
@@ -266,93 +332,27 @@ static inline void fill_pb_page(struct pbe *pbpage)
 /**
  *     create_pbe_list - Create a list of PBEs on top of a given chain
  *     of memory pages allocated with alloc_pagedir()
+ *
+ *     This function assumes that pages allocated by alloc_image_page() will
+ *     always be zeroed.
  */
 
 static inline void create_pbe_list(struct pbe *pblist, unsigned int nr_pages)
 {
-       struct pbe *pbpage, *p;
+       struct pbe *pbpage;
        unsigned int num = PBES_PER_PAGE;
 
        for_each_pb_page (pbpage, pblist) {
                if (num >= nr_pages)
                        break;
 
-               fill_pb_page(pbpage);
+               fill_pb_page(pbpage, PBES_PER_PAGE);
                num += PBES_PER_PAGE;
        }
        if (pbpage) {
-               for (num -= PBES_PER_PAGE - 1, p = pbpage; num < nr_pages; p++, num++)
-                       p->next = p + 1;
-               p->next = NULL;
-       }
-}
-
-/**
- *     On resume it is necessary to trace and eventually free the unsafe
- *     pages that have been allocated, because they are needed for I/O
- *     (on x86-64 we likely will "eat" these pages once again while
- *     creating the temporary page translation tables)
- */
-
-struct eaten_page {
-       struct eaten_page *next;
-       char padding[PAGE_SIZE - sizeof(void *)];
-};
-
-static struct eaten_page *eaten_pages = NULL;
-
-void release_eaten_pages(void)
-{
-       struct eaten_page *p, *q;
-
-       p = eaten_pages;
-       while (p) {
-               q = p->next;
-               /* We don't want swsusp_free() to free this page again */
-               ClearPageNosave(virt_to_page(p));
-               free_page((unsigned long)p);
-               p = q;
+               num -= PBES_PER_PAGE;
+               fill_pb_page(pbpage, nr_pages - num);
        }
-       eaten_pages = NULL;
-}
-
-/**
- *     @safe_needed - on resume, for storing the PBE list and the image,
- *     we can only use memory pages that do not conflict with the pages
- *     which had been used before suspend.
- *
- *     The unsafe pages are marked with the PG_nosave_free flag
- *
- *     Allocated but unusable (ie eaten) memory pages should be marked
- *     so that swsusp_free() can release them
- */
-
-static inline void *alloc_image_page(gfp_t gfp_mask, int safe_needed)
-{
-       void *res;
-
-       if (safe_needed)
-               do {
-                       res = (void *)get_zeroed_page(gfp_mask);
-                       if (res && PageNosaveFree(virt_to_page(res))) {
-                               /* This is for swsusp_free() */
-                               SetPageNosave(virt_to_page(res));
-                               ((struct eaten_page *)res)->next = eaten_pages;
-                               eaten_pages = res;
-                       }
-               } while (res && PageNosaveFree(virt_to_page(res)));
-       else
-               res = (void *)get_zeroed_page(gfp_mask);
-       if (res) {
-               SetPageNosave(virt_to_page(res));
-               SetPageNosaveFree(virt_to_page(res));
-       }
-       return res;
-}
-
-unsigned long get_safe_page(gfp_t gfp_mask)
-{
-       return (unsigned long)alloc_image_page(gfp_mask, 1);
 }
 
 /**
@@ -368,7 +368,8 @@ unsigned long get_safe_page(gfp_t gfp_mask)
  *     On each page we set up a list of struct_pbe elements.
  */
 
-struct pbe *alloc_pagedir(unsigned int nr_pages, gfp_t gfp_mask, int safe_needed)
+static struct pbe *alloc_pagedir(unsigned int nr_pages, gfp_t gfp_mask,
+                                int safe_needed)
 {
        unsigned int num;
        struct pbe *pblist, *pbe;
@@ -376,19 +377,18 @@ struct pbe *alloc_pagedir(unsigned int nr_pages, gfp_t gfp_mask, int safe_needed
        if (!nr_pages)
                return NULL;
 
-       pr_debug("alloc_pagedir(): nr_pages = %d\n", nr_pages);
        pblist = alloc_image_page(gfp_mask, safe_needed);
-       /* FIXME: rewrite this ugly loop */
-       for (pbe = pblist, num = PBES_PER_PAGE; pbe && num < nr_pages;
-                       pbe = pbe->next, num += PBES_PER_PAGE) {
+       pbe = pblist;
+       for (num = PBES_PER_PAGE; num < nr_pages; num += PBES_PER_PAGE) {
+               if (!pbe) {
+                       free_pagedir(pblist, 1);
+                       return NULL;
+               }
                pbe += PB_PAGE_SKIP;
                pbe->next = alloc_image_page(gfp_mask, safe_needed);
+               pbe = pbe->next;
        }
-       if (!pbe) { /* get_zeroed_page() failed */
-               free_pagedir(pblist);
-               pblist = NULL;
-        } else
-               create_pbe_list(pblist, nr_pages);
+       create_pbe_list(pblist, nr_pages);
        return pblist;
 }
 
@@ -400,13 +400,14 @@ struct pbe *alloc_pagedir(unsigned int nr_pages, gfp_t gfp_mask, int safe_needed
 void swsusp_free(void)
 {
        struct zone *zone;
-       unsigned long zone_pfn;
+       unsigned long pfn, max_zone_pfn;
 
        for_each_zone(zone) {
-               for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn)
-                       if (pfn_valid(zone_pfn + zone->zone_start_pfn)) {
-                               struct page *page;
-                               page = pfn_to_page(zone_pfn + zone->zone_start_pfn);
+               max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
+               for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
+                       if (pfn_valid(pfn)) {
+                               struct page *page = pfn_to_page(pfn);
+
                                if (PageNosave(page) && PageNosaveFree(page)) {
                                        ClearPageNosave(page);
                                        ClearPageNosaveFree(page);
@@ -414,6 +415,10 @@ void swsusp_free(void)
                                }
                        }
        }
+       nr_copy_pages = 0;
+       nr_meta_pages = 0;
+       restore_pblist = NULL;
+       buffer = NULL;
 }
 
 
@@ -437,7 +442,7 @@ static int enough_free_mem(unsigned int nr_pages)
                (nr_pages + PBES_PER_PAGE - 1) / PBES_PER_PAGE);
 }
 
-int alloc_data_pages(struct pbe *pblist, gfp_t gfp_mask, int safe_needed)
+static int alloc_data_pages(struct pbe *pblist, gfp_t gfp_mask, int safe_needed)
 {
        struct pbe *p;
 
@@ -487,15 +492,15 @@ asmlinkage int swsusp_save(void)
                return -ENOMEM;
        }
 
-       pagedir_nosave = swsusp_alloc(nr_pages);
-       if (!pagedir_nosave)
+       restore_pblist = swsusp_alloc(nr_pages);
+       if (!restore_pblist)
                return -ENOMEM;
 
        /* During allocating of suspend pagedir, new cold pages may appear.
         * Kill them.
         */
        drain_local_pages();
-       copy_data_pages(pagedir_nosave);
+       copy_data_pages(restore_pblist);
 
        /*
         * End of critical section. From now on, we can write to memory,
@@ -504,7 +509,383 @@ asmlinkage int swsusp_save(void)
         */
 
        nr_copy_pages = nr_pages;
+       nr_meta_pages = (nr_pages * sizeof(long) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 
        printk("swsusp: critical section/: done (%d pages copied)\n", nr_pages);
        return 0;
 }
+
+static void init_header(struct swsusp_info *info)
+{
+       memset(info, 0, sizeof(struct swsusp_info));
+       info->version_code = LINUX_VERSION_CODE;
+       info->num_physpages = num_physpages;
+       memcpy(&info->uts, &system_utsname, sizeof(system_utsname));
+       info->cpus = num_online_cpus();
+       info->image_pages = nr_copy_pages;
+       info->pages = nr_copy_pages + nr_meta_pages + 1;
+       info->size = info->pages;
+       info->size <<= PAGE_SHIFT;
+}
+
+/**
+ *     pack_orig_addresses - the .orig_address fields of the PBEs from the
+ *     list starting at @pbe are stored in the array @buf[] (1 page)
+ */
+
+static inline struct pbe *pack_orig_addresses(unsigned long *buf, struct pbe *pbe)
+{
+       int j;
+
+       for (j = 0; j < PAGE_SIZE / sizeof(long) && pbe; j++) {
+               buf[j] = pbe->orig_address;
+               pbe = pbe->next;
+       }
+       if (!pbe)
+               for (; j < PAGE_SIZE / sizeof(long); j++)
+                       buf[j] = 0;
+       return pbe;
+}
+
+/**
+ *     snapshot_read_next - used for reading the system memory snapshot.
+ *
+ *     On the first call to it @handle should point to a zeroed
+ *     snapshot_handle structure.  The structure gets updated and a pointer
+ *     to it should be passed to this function every next time.
+ *
+ *     The @count parameter should contain the number of bytes the caller
+ *     wants to read from the snapshot.  It must not be zero.
+ *
+ *     On success the function returns a positive number.  Then, the caller
+ *     is allowed to read up to the returned number of bytes from the memory
+ *     location computed by the data_of() macro.  The number returned
+ *     may be smaller than @count, but this only happens if the read would
+ *     cross a page boundary otherwise.
+ *
+ *     The function returns 0 to indicate the end of data stream condition,
+ *     and a negative number is returned on error.  In such cases the
+ *     structure pointed to by @handle is not updated and should not be used
+ *     any more.
+ */
+
+int snapshot_read_next(struct snapshot_handle *handle, size_t count)
+{
+       if (handle->cur > nr_meta_pages + nr_copy_pages)
+               return 0;
+       if (!buffer) {
+               /* This makes the buffer be freed by swsusp_free() */
+               buffer = alloc_image_page(GFP_ATOMIC, 0);
+               if (!buffer)
+                       return -ENOMEM;
+       }
+       if (!handle->offset) {
+               init_header((struct swsusp_info *)buffer);
+               handle->buffer = buffer;
+               handle->pbe = restore_pblist;
+       }
+       if (handle->prev < handle->cur) {
+               if (handle->cur <= nr_meta_pages) {
+                       handle->pbe = pack_orig_addresses(buffer, handle->pbe);
+                       if (!handle->pbe)
+                               handle->pbe = restore_pblist;
+               } else {
+                       handle->buffer = (void *)handle->pbe->address;
+                       handle->pbe = handle->pbe->next;
+               }
+               handle->prev = handle->cur;
+       }
+       handle->buf_offset = handle->cur_offset;
+       if (handle->cur_offset + count >= PAGE_SIZE) {
+               count = PAGE_SIZE - handle->cur_offset;
+               handle->cur_offset = 0;
+               handle->cur++;
+       } else {
+               handle->cur_offset += count;
+       }
+       handle->offset += count;
+       return count;
+}
+
+/**
+ *     mark_unsafe_pages - mark the pages that cannot be used for storing
+ *     the image during resume, because they conflict with the pages that
+ *     had been used before suspend
+ */
+
+static int mark_unsafe_pages(struct pbe *pblist)
+{
+       struct zone *zone;
+       unsigned long pfn, max_zone_pfn;
+       struct pbe *p;
+
+       if (!pblist) /* a sanity check */
+               return -EINVAL;
+
+       /* Clear page flags */
+       for_each_zone (zone) {
+               max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
+               for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
+                       if (pfn_valid(pfn))
+                               ClearPageNosaveFree(pfn_to_page(pfn));
+       }
+
+       /* Mark orig addresses */
+       for_each_pbe (p, pblist) {
+               if (virt_addr_valid(p->orig_address))
+                       SetPageNosaveFree(virt_to_page(p->orig_address));
+               else
+                       return -EFAULT;
+       }
+
+       unsafe_pages = 0;
+
+       return 0;
+}
+
+static void copy_page_backup_list(struct pbe *dst, struct pbe *src)
+{
+       /* We assume both lists contain the same number of elements */
+       while (src) {
+               dst->orig_address = src->orig_address;
+               dst = dst->next;
+               src = src->next;
+       }
+}
+
+static int check_header(struct swsusp_info *info)
+{
+       char *reason = NULL;
+
+       if (info->version_code != LINUX_VERSION_CODE)
+               reason = "kernel version";
+       if (info->num_physpages != num_physpages)
+               reason = "memory size";
+       if (strcmp(info->uts.sysname,system_utsname.sysname))
+               reason = "system type";
+       if (strcmp(info->uts.release,system_utsname.release))
+               reason = "kernel release";
+       if (strcmp(info->uts.version,system_utsname.version))
+               reason = "version";
+       if (strcmp(info->uts.machine,system_utsname.machine))
+               reason = "machine";
+       if (reason) {
+               printk(KERN_ERR "swsusp: Resume mismatch: %s\n", reason);
+               return -EPERM;
+       }
+       return 0;
+}
+
+/**
+ *     load header - check the image header and copy data from it
+ */
+
+static int load_header(struct snapshot_handle *handle,
+                              struct swsusp_info *info)
+{
+       int error;
+       struct pbe *pblist;
+
+       error = check_header(info);
+       if (!error) {
+               pblist = alloc_pagedir(info->image_pages, GFP_ATOMIC, 0);
+               if (!pblist)
+                       return -ENOMEM;
+               restore_pblist = pblist;
+               handle->pbe = pblist;
+               nr_copy_pages = info->image_pages;
+               nr_meta_pages = info->pages - info->image_pages - 1;
+       }
+       return error;
+}
+
+/**
+ *     unpack_orig_addresses - copy the elements of @buf[] (1 page) to
+ *     the PBEs in the list starting at @pbe
+ */
+
+static inline struct pbe *unpack_orig_addresses(unsigned long *buf,
+                                                struct pbe *pbe)
+{
+       int j;
+
+       for (j = 0; j < PAGE_SIZE / sizeof(long) && pbe; j++) {
+               pbe->orig_address = buf[j];
+               pbe = pbe->next;
+       }
+       return pbe;
+}
+
+/**
+ *     prepare_image - use metadata contained in the PBE list
+ *     pointed to by restore_pblist to mark the pages that will
+ *     be overwritten in the process of restoring the system
+ *     memory state from the image ("unsafe" pages) and allocate
+ *     memory for the image
+ *
+ *     The idea is to allocate the PBE list first and then
+ *     allocate as many pages as it's needed for the image data,
+ *     but not to assign these pages to the PBEs initially.
+ *     Instead, we just mark them as allocated and create a list
+ *     of "safe" which will be used later
+ */
+
+struct safe_page {
+       struct safe_page *next;
+       char padding[PAGE_SIZE - sizeof(void *)];
+};
+
+static struct safe_page *safe_pages;
+
+static int prepare_image(struct snapshot_handle *handle)
+{
+       int error = 0;
+       unsigned int nr_pages = nr_copy_pages;
+       struct pbe *p, *pblist = NULL;
+
+       p = restore_pblist;
+       error = mark_unsafe_pages(p);
+       if (!error) {
+               pblist = alloc_pagedir(nr_pages, GFP_ATOMIC, 1);
+               if (pblist)
+                       copy_page_backup_list(pblist, p);
+               free_pagedir(p, 0);
+               if (!pblist)
+                       error = -ENOMEM;
+       }
+       safe_pages = NULL;
+       if (!error && nr_pages > unsafe_pages) {
+               nr_pages -= unsafe_pages;
+               while (nr_pages--) {
+                       struct safe_page *ptr;
+
+                       ptr = (struct safe_page *)get_zeroed_page(GFP_ATOMIC);
+                       if (!ptr) {
+                               error = -ENOMEM;
+                               break;
+                       }
+                       if (!PageNosaveFree(virt_to_page(ptr))) {
+                               /* The page is "safe", add it to the list */
+                               ptr->next = safe_pages;
+                               safe_pages = ptr;
+                       }
+                       /* Mark the page as allocated */
+                       SetPageNosave(virt_to_page(ptr));
+                       SetPageNosaveFree(virt_to_page(ptr));
+               }
+       }
+       if (!error) {
+               restore_pblist = pblist;
+       } else {
+               handle->pbe = NULL;
+               swsusp_free();
+       }
+       return error;
+}
+
+static void *get_buffer(struct snapshot_handle *handle)
+{
+       struct pbe *pbe = handle->pbe, *last = handle->last_pbe;
+       struct page *page = virt_to_page(pbe->orig_address);
+
+       if (PageNosave(page) && PageNosaveFree(page)) {
+               /*
+                * We have allocated the "original" page frame and we can
+                * use it directly to store the read page
+                */
+               pbe->address = 0;
+               if (last && last->next)
+                       last->next = NULL;
+               return (void *)pbe->orig_address;
+       }
+       /*
+        * The "original" page frame has not been allocated and we have to
+        * use a "safe" page frame to store the read page
+        */
+       pbe->address = (unsigned long)safe_pages;
+       safe_pages = safe_pages->next;
+       if (last)
+               last->next = pbe;
+       handle->last_pbe = pbe;
+       return (void *)pbe->address;
+}
+
+/**
+ *     snapshot_write_next - used for writing the system memory snapshot.
+ *
+ *     On the first call to it @handle should point to a zeroed
+ *     snapshot_handle structure.  The structure gets updated and a pointer
+ *     to it should be passed to this function every next time.
+ *
+ *     The @count parameter should contain the number of bytes the caller
+ *     wants to write to the image.  It must not be zero.
+ *
+ *     On success the function returns a positive number.  Then, the caller
+ *     is allowed to write up to the returned number of bytes to the memory
+ *     location computed by the data_of() macro.  The number returned
+ *     may be smaller than @count, but this only happens if the write would
+ *     cross a page boundary otherwise.
+ *
+ *     The function returns 0 to indicate the "end of file" condition,
+ *     and a negative number is returned on error.  In such cases the
+ *     structure pointed to by @handle is not updated and should not be used
+ *     any more.
+ */
+
+int snapshot_write_next(struct snapshot_handle *handle, size_t count)
+{
+       int error = 0;
+
+       if (handle->prev && handle->cur > nr_meta_pages + nr_copy_pages)
+               return 0;
+       if (!buffer) {
+               /* This makes the buffer be freed by swsusp_free() */
+               buffer = alloc_image_page(GFP_ATOMIC, 0);
+               if (!buffer)
+                       return -ENOMEM;
+       }
+       if (!handle->offset)
+               handle->buffer = buffer;
+       handle->sync_read = 1;
+       if (handle->prev < handle->cur) {
+               if (!handle->prev) {
+                       error = load_header(handle,
+                                       (struct swsusp_info *)buffer);
+                       if (error)
+                               return error;
+               } else if (handle->prev <= nr_meta_pages) {
+                       handle->pbe = unpack_orig_addresses(buffer,
+                                                       handle->pbe);
+                       if (!handle->pbe) {
+                               error = prepare_image(handle);
+                               if (error)
+                                       return error;
+                               handle->pbe = restore_pblist;
+                               handle->last_pbe = NULL;
+                               handle->buffer = get_buffer(handle);
+                               handle->sync_read = 0;
+                       }
+               } else {
+                       handle->pbe = handle->pbe->next;
+                       handle->buffer = get_buffer(handle);
+                       handle->sync_read = 0;
+               }
+               handle->prev = handle->cur;
+       }
+       handle->buf_offset = handle->cur_offset;
+       if (handle->cur_offset + count >= PAGE_SIZE) {
+               count = PAGE_SIZE - handle->cur_offset;
+               handle->cur_offset = 0;
+               handle->cur++;
+       } else {
+               handle->cur_offset += count;
+       }
+       handle->offset += count;
+       return count;
+}
+
+int snapshot_image_loaded(struct snapshot_handle *handle)
+{
+       return !(!handle->pbe || handle->pbe->next || !nr_copy_pages ||
+               handle->cur <= nr_meta_pages + nr_copy_pages);
+}