[PATCH] swsusp: low level interface
Introduce the low level interface that can be used for handling the
snapshot of the system memory by the in-kernel swap-writing/reading code of
swsusp and the userland interface code (to be introduced shortly).
Also change the way in which swsusp records the allocated swap pages and,
consequently, simplifies the in-kernel swap-writing/reading code (this is
necessary for the userland interface too). To this end, it introduces two
helper functions in mm/swapfile.c, so that the swsusp code does not refer
directly to the swap internals.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 12415dd..54eac8a 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -234,14 +234,15 @@
/* linux/mm/swapfile.c */
extern long total_swap_pages;
extern unsigned int nr_swapfiles;
-extern struct swap_info_struct swap_info[];
extern void si_swapinfo(struct sysinfo *);
extern swp_entry_t get_swap_page(void);
-extern swp_entry_t get_swap_page_of_type(int type);
+extern swp_entry_t get_swap_page_of_type(int);
extern int swap_duplicate(swp_entry_t);
extern int valid_swaphandles(swp_entry_t, unsigned long *);
extern void swap_free(swp_entry_t);
extern void free_swap_and_cache(swp_entry_t);
+extern int swap_type_of(dev_t);
+extern unsigned int count_swap_pages(int, int);
extern sector_t map_swap_page(struct swap_info_struct *, pgoff_t);
extern struct swap_info_struct *get_swap_info_struct(unsigned);
extern int can_share_swap_page(struct page *);
diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index 0b43847..4eb464b 100644
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -26,9 +26,9 @@
extern int swsusp_shrink_memory(void);
extern int swsusp_suspend(void);
-extern int swsusp_write(struct pbe *pblist, unsigned int nr_pages);
+extern int swsusp_write(void);
extern int swsusp_check(void);
-extern int swsusp_read(struct pbe **pblist_ptr);
+extern int swsusp_read(void);
extern void swsusp_close(void);
extern int swsusp_resume(void);
@@ -70,10 +70,6 @@
while(1);
}
-
-static int in_suspend __nosavedata = 0;
-
-
static inline void platform_finish(void)
{
if (pm_disk_mode == PM_DISK_PLATFORM) {
@@ -145,7 +141,7 @@
if (in_suspend) {
device_resume();
pr_debug("PM: writing image.\n");
- error = swsusp_write(pagedir_nosave, nr_copy_pages);
+ error = swsusp_write();
if (!error)
power_down(pm_disk_mode);
else {
@@ -216,7 +212,7 @@
pr_debug("PM: Reading swsusp image.\n");
- if ((error = swsusp_read(&pagedir_nosave))) {
+ if ((error = swsusp_read())) {
swsusp_free();
goto Thaw;
}
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 388dba6..ea7132e 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -37,21 +37,31 @@
/* References to section boundaries */
extern const void __nosave_begin, __nosave_end;
-extern unsigned int nr_copy_pages;
extern struct pbe *pagedir_nosave;
/* Preferred image size in bytes (default 500 MB) */
extern unsigned long image_size;
+extern int in_suspend;
+
extern asmlinkage int swsusp_arch_suspend(void);
extern asmlinkage int swsusp_arch_resume(void);
extern unsigned int count_data_pages(void);
-extern void free_pagedir(struct pbe *pblist);
-extern void release_eaten_pages(void);
-extern struct pbe *alloc_pagedir(unsigned nr_pages, gfp_t gfp_mask, int safe_needed);
extern void swsusp_free(void);
-extern int alloc_data_pages(struct pbe *pblist, gfp_t gfp_mask, int safe_needed);
-extern unsigned int snapshot_nr_pages(void);
-extern struct pbe *snapshot_pblist(void);
-extern void snapshot_pblist_set(struct pbe *pblist);
+
+struct snapshot_handle {
+ loff_t offset;
+ unsigned int page;
+ unsigned int page_offset;
+ unsigned int prev;
+ struct pbe *pbe;
+ void *buffer;
+ unsigned int buf_offset;
+};
+
+#define data_of(handle) ((handle).buffer + (handle).buf_offset)
+
+extern int snapshot_read_next(struct snapshot_handle *handle, size_t count);
+extern int snapshot_write_next(struct snapshot_handle *handle, size_t count);
+int snapshot_image_loaded(struct snapshot_handle *handle);
diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 8d5a598..cc34943 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -10,6 +10,7 @@
*/
+#include <linux/version.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/suspend.h>
@@ -34,7 +35,8 @@
#include "power.h"
struct pbe *pagedir_nosave;
-unsigned int nr_copy_pages;
+static unsigned int nr_copy_pages;
+static unsigned int nr_meta_pages;
#ifdef CONFIG_HIGHMEM
unsigned int count_highmem_pages(void)
@@ -235,7 +237,7 @@
* free_pagedir - free pages allocated with alloc_pagedir()
*/
-void free_pagedir(struct pbe *pblist)
+static void free_pagedir(struct pbe *pblist)
{
struct pbe *pbe;
@@ -301,7 +303,7 @@
static struct eaten_page *eaten_pages = NULL;
-void release_eaten_pages(void)
+static void release_eaten_pages(void)
{
struct eaten_page *p, *q;
@@ -376,7 +378,6 @@
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;
@@ -414,6 +415,9 @@
}
}
}
+ nr_copy_pages = 0;
+ nr_meta_pages = 0;
+ pagedir_nosave = NULL;
}
@@ -437,7 +441,7 @@
(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;
@@ -504,7 +508,319 @@
*/
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;
+}
+
+/**
+ * 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)
+{
+ static unsigned long *buffer;
+
+ if (handle->page > 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 = pagedir_nosave;
+ }
+ if (handle->prev < handle->page) {
+ if (handle->page <= nr_meta_pages) {
+ handle->pbe = pack_orig_addresses(buffer, handle->pbe);
+ if (!handle->pbe)
+ handle->pbe = pagedir_nosave;
+ } else {
+ handle->buffer = (void *)handle->pbe->address;
+ handle->pbe = handle->pbe->next;
+ }
+ handle->prev = handle->page;
+ }
+ handle->buf_offset = handle->page_offset;
+ if (handle->page_offset + count >= PAGE_SIZE) {
+ count = PAGE_SIZE - handle->page_offset;
+ handle->page_offset = 0;
+ handle->page++;
+ } else {
+ handle->page_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 zone_pfn;
+ struct pbe *p;
+
+ if (!pblist) /* a sanity check */
+ return -EINVAL;
+
+ /* Clear page flags */
+ for_each_zone (zone) {
+ for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn)
+ if (pfn_valid(zone_pfn + zone->zone_start_pfn))
+ ClearPageNosaveFree(pfn_to_page(zone_pfn +
+ zone->zone_start_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;
+ }
+
+ 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;
+ pagedir_nosave = 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;
+}
+
+/**
+ * create_image - use metadata contained in the PBE list
+ * pointed to by pagedir_nosave to mark the pages that will
+ * be overwritten in the process of restoring the system
+ * memory state from the image and allocate memory for
+ * the image avoiding these pages
+ */
+
+static int create_image(struct snapshot_handle *handle)
+{
+ int error = 0;
+ struct pbe *p, *pblist;
+
+ p = pagedir_nosave;
+ error = mark_unsafe_pages(p);
+ if (!error) {
+ pblist = alloc_pagedir(nr_copy_pages, GFP_ATOMIC, 1);
+ if (pblist)
+ copy_page_backup_list(pblist, p);
+ free_pagedir(p);
+ if (!pblist)
+ error = -ENOMEM;
+ }
+ if (!error)
+ error = alloc_data_pages(pblist, GFP_ATOMIC, 1);
+ if (!error) {
+ release_eaten_pages();
+ pagedir_nosave = pblist;
+ } else {
+ pagedir_nosave = NULL;
+ handle->pbe = NULL;
+ nr_copy_pages = 0;
+ nr_meta_pages = 0;
+ }
+ return error;
+}
+
+/**
+ * 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)
+{
+ static unsigned long *buffer;
+ int error = 0;
+
+ if (handle->prev && handle->page > 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;
+ if (handle->prev < handle->page) {
+ 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 = create_image(handle);
+ if (error)
+ return error;
+ handle->pbe = pagedir_nosave;
+ handle->buffer = (void *)handle->pbe->address;
+ }
+ } else {
+ handle->pbe = handle->pbe->next;
+ handle->buffer = (void *)handle->pbe->address;
+ }
+ handle->prev = handle->page;
+ }
+ handle->buf_offset = handle->page_offset;
+ if (handle->page_offset + count >= PAGE_SIZE) {
+ count = PAGE_SIZE - handle->page_offset;
+ handle->page_offset = 0;
+ handle->page++;
+ } else {
+ handle->page_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->page <= nr_meta_pages + nr_copy_pages);
+}
diff --git a/kernel/power/swsusp.c b/kernel/power/swsusp.c
index 4e90905..457084f 100644
--- a/kernel/power/swsusp.c
+++ b/kernel/power/swsusp.c
@@ -77,6 +77,8 @@
*/
unsigned long image_size = 500 * 1024 * 1024;
+int in_suspend __nosavedata = 0;
+
#ifdef CONFIG_HIGHMEM
unsigned int count_highmem_pages(void);
int save_highmem(void);
@@ -98,8 +100,6 @@
char sig[10];
} __attribute__((packed, aligned(PAGE_SIZE))) swsusp_header;
-static struct swsusp_info swsusp_info;
-
/*
* Saving part...
*/
@@ -129,255 +129,261 @@
return error;
}
-/*
- * Check whether the swap device is the specified resume
- * device, irrespective of whether they are specified by
- * identical names.
- *
- * (Thus, device inode aliasing is allowed. You can say /dev/hda4
- * instead of /dev/ide/host0/bus0/target0/lun0/part4 [if using devfs]
- * and they'll be considered the same device. This is *necessary* for
- * devfs, since the resume code can only recognize the form /dev/hda4,
- * but the suspend code would see the long name.)
+/**
+ * swsusp_swap_check - check if the resume device is a swap device
+ * and get its index (if so)
*/
-static inline int is_resume_device(const struct swap_info_struct *swap_info)
-{
- struct file *file = swap_info->swap_file;
- struct inode *inode = file->f_dentry->d_inode;
-
- return S_ISBLK(inode->i_mode) &&
- swsusp_resume_device == MKDEV(imajor(inode), iminor(inode));
-}
static int swsusp_swap_check(void) /* This is called before saving image */
{
- int i;
+ int res = swap_type_of(swsusp_resume_device);
- if (!swsusp_resume_device)
- return -ENODEV;
- spin_lock(&swap_lock);
- for (i = 0; i < MAX_SWAPFILES; i++) {
- if (!(swap_info[i].flags & SWP_WRITEOK))
- continue;
- if (is_resume_device(swap_info + i)) {
- spin_unlock(&swap_lock);
- root_swap = i;
- return 0;
- }
+ if (res >= 0) {
+ root_swap = res;
+ return 0;
}
- spin_unlock(&swap_lock);
- return -ENODEV;
+ return res;
}
/**
- * write_page - Write one page to a fresh swap location.
- * @addr: Address we're writing.
- * @loc: Place to store the entry we used.
+ * The bitmap is used for tracing allocated swap pages
*
- * Allocate a new swap entry and 'sync' it. Note we discard -EIO
- * errors. That is an artifact left over from swsusp. It did not
- * check the return of rw_swap_page_sync() at all, since most pages
- * written back to swap would return -EIO.
- * This is a partial improvement, since we will at least return other
- * errors, though we need to eventually fix the damn code.
+ * The entire bitmap consists of a number of bitmap_page
+ * structures linked with the help of the .next member.
+ * Thus each page can be allocated individually, so we only
+ * need to make 0-order memory allocations to create
+ * the bitmap.
*/
-static int write_page(unsigned long addr, swp_entry_t *loc)
+
+#define BITMAP_PAGE_SIZE (PAGE_SIZE - sizeof(void *))
+#define BITMAP_PAGE_CHUNKS (BITMAP_PAGE_SIZE / sizeof(long))
+#define BITS_PER_CHUNK (sizeof(long) * 8)
+#define BITMAP_PAGE_BITS (BITMAP_PAGE_CHUNKS * BITS_PER_CHUNK)
+
+struct bitmap_page {
+ unsigned long chunks[BITMAP_PAGE_CHUNKS];
+ struct bitmap_page *next;
+};
+
+/**
+ * The following functions are used for tracing the allocated
+ * swap pages, so that they can be freed in case of an error.
+ *
+ * The functions operate on a linked bitmap structure defined
+ * above
+ */
+
+static void free_bitmap(struct bitmap_page *bitmap)
+{
+ struct bitmap_page *bp;
+
+ while (bitmap) {
+ bp = bitmap->next;
+ free_page((unsigned long)bitmap);
+ bitmap = bp;
+ }
+}
+
+static struct bitmap_page *alloc_bitmap(unsigned int nr_bits)
+{
+ struct bitmap_page *bitmap, *bp;
+ unsigned int n;
+
+ if (!nr_bits)
+ return NULL;
+
+ bitmap = (struct bitmap_page *)get_zeroed_page(GFP_KERNEL);
+ bp = bitmap;
+ for (n = BITMAP_PAGE_BITS; n < nr_bits; n += BITMAP_PAGE_BITS) {
+ bp->next = (struct bitmap_page *)get_zeroed_page(GFP_KERNEL);
+ bp = bp->next;
+ if (!bp) {
+ free_bitmap(bitmap);
+ return NULL;
+ }
+ }
+ return bitmap;
+}
+
+static int bitmap_set(struct bitmap_page *bitmap, unsigned long bit)
+{
+ unsigned int n;
+
+ n = BITMAP_PAGE_BITS;
+ while (bitmap && n <= bit) {
+ n += BITMAP_PAGE_BITS;
+ bitmap = bitmap->next;
+ }
+ if (!bitmap)
+ return -EINVAL;
+ n -= BITMAP_PAGE_BITS;
+ bit -= n;
+ n = 0;
+ while (bit >= BITS_PER_CHUNK) {
+ bit -= BITS_PER_CHUNK;
+ n++;
+ }
+ bitmap->chunks[n] |= (1UL << bit);
+ return 0;
+}
+
+static unsigned long alloc_swap_page(int swap, struct bitmap_page *bitmap)
+{
+ unsigned long offset;
+
+ offset = swp_offset(get_swap_page_of_type(swap));
+ if (offset) {
+ if (bitmap_set(bitmap, offset)) {
+ swap_free(swp_entry(swap, offset));
+ offset = 0;
+ }
+ }
+ return offset;
+}
+
+static void free_all_swap_pages(int swap, struct bitmap_page *bitmap)
+{
+ unsigned int bit, n;
+ unsigned long test;
+
+ bit = 0;
+ while (bitmap) {
+ for (n = 0; n < BITMAP_PAGE_CHUNKS; n++)
+ for (test = 1UL; test; test <<= 1) {
+ if (bitmap->chunks[n] & test)
+ swap_free(swp_entry(swap, bit));
+ bit++;
+ }
+ bitmap = bitmap->next;
+ }
+}
+
+/**
+ * write_page - Write one page to given swap location.
+ * @buf: Address we're writing.
+ * @offset: Offset of the swap page we're writing to.
+ */
+
+static int write_page(void *buf, unsigned long offset)
{
swp_entry_t entry;
int error = -ENOSPC;
- entry = get_swap_page_of_type(root_swap);
- if (swp_offset(entry)) {
- error = rw_swap_page_sync(WRITE, entry, virt_to_page(addr));
- if (!error || error == -EIO)
- *loc = entry;
+ if (offset) {
+ entry = swp_entry(root_swap, offset);
+ error = rw_swap_page_sync(WRITE, entry, virt_to_page(buf));
}
return error;
}
-/**
- * Swap map-handling functions
- *
+/*
* The swap map is a data structure used for keeping track of each page
- * written to the swap. It consists of many swap_map_page structures
- * that contain each an array of MAP_PAGE_SIZE swap entries.
- * These structures are linked together with the help of either the
- * .next (in memory) or the .next_swap (in swap) member.
+ * written to a swap partition. It consists of many swap_map_page
+ * structures that contain each an array of MAP_PAGE_SIZE swap entries.
+ * These structures are stored on the swap and linked together with the
+ * help of the .next_swap member.
*
- * The swap map is created during suspend. At that time we need to keep
- * it in memory, because we have to free all of the allocated swap
- * entries if an error occurs. The memory needed is preallocated
- * so that we know in advance if there's enough of it.
+ * The swap map is created during suspend. The swap map pages are
+ * allocated and populated one at a time, so we only need one memory
+ * page to set up the entire structure.
*
- * The first swap_map_page structure is filled with the swap entries that
- * correspond to the first MAP_PAGE_SIZE data pages written to swap and
- * so on. After the all of the data pages have been written, the order
- * of the swap_map_page structures in the map is reversed so that they
- * can be read from swap in the original order. This causes the data
- * pages to be loaded in exactly the same order in which they have been
- * saved.
- *
- * During resume we only need to use one swap_map_page structure
- * at a time, which means that we only need to use two memory pages for
- * reading the image - one for reading the swap_map_page structures
- * and the second for reading the data pages from swap.
+ * During resume we also only need to use one swap_map_page structure
+ * at a time.
*/
-#define MAP_PAGE_SIZE ((PAGE_SIZE - sizeof(swp_entry_t) - sizeof(void *)) \
- / sizeof(swp_entry_t))
+#define MAP_PAGE_ENTRIES (PAGE_SIZE / sizeof(long) - 1)
struct swap_map_page {
- swp_entry_t entries[MAP_PAGE_SIZE];
- swp_entry_t next_swap;
- struct swap_map_page *next;
+ unsigned long entries[MAP_PAGE_ENTRIES];
+ unsigned long next_swap;
};
-static inline void free_swap_map(struct swap_map_page *swap_map)
-{
- struct swap_map_page *swp;
-
- while (swap_map) {
- swp = swap_map->next;
- free_page((unsigned long)swap_map);
- swap_map = swp;
- }
-}
-
-static struct swap_map_page *alloc_swap_map(unsigned int nr_pages)
-{
- struct swap_map_page *swap_map, *swp;
- unsigned n = 0;
-
- if (!nr_pages)
- return NULL;
-
- pr_debug("alloc_swap_map(): nr_pages = %d\n", nr_pages);
- swap_map = (struct swap_map_page *)get_zeroed_page(GFP_ATOMIC);
- swp = swap_map;
- for (n = MAP_PAGE_SIZE; n < nr_pages; n += MAP_PAGE_SIZE) {
- swp->next = (struct swap_map_page *)get_zeroed_page(GFP_ATOMIC);
- swp = swp->next;
- if (!swp) {
- free_swap_map(swap_map);
- return NULL;
- }
- }
- return swap_map;
-}
-
/**
- * reverse_swap_map - reverse the order of pages in the swap map
- * @swap_map
- */
-
-static inline struct swap_map_page *reverse_swap_map(struct swap_map_page *swap_map)
-{
- struct swap_map_page *prev, *next;
-
- prev = NULL;
- while (swap_map) {
- next = swap_map->next;
- swap_map->next = prev;
- prev = swap_map;
- swap_map = next;
- }
- return prev;
-}
-
-/**
- * free_swap_map_entries - free the swap entries allocated to store
- * the swap map @swap_map (this is only called in case of an error)
- */
-static inline void free_swap_map_entries(struct swap_map_page *swap_map)
-{
- while (swap_map) {
- if (swap_map->next_swap.val)
- swap_free(swap_map->next_swap);
- swap_map = swap_map->next;
- }
-}
-
-/**
- * save_swap_map - save the swap map used for tracing the data pages
- * stored in the swap
- */
-
-static int save_swap_map(struct swap_map_page *swap_map, swp_entry_t *start)
-{
- swp_entry_t entry = (swp_entry_t){0};
- int error;
-
- while (swap_map) {
- swap_map->next_swap = entry;
- if ((error = write_page((unsigned long)swap_map, &entry)))
- return error;
- swap_map = swap_map->next;
- }
- *start = entry;
- return 0;
-}
-
-/**
- * free_image_entries - free the swap entries allocated to store
- * the image data pages (this is only called in case of an error)
- */
-
-static inline void free_image_entries(struct swap_map_page *swp)
-{
- unsigned k;
-
- while (swp) {
- for (k = 0; k < MAP_PAGE_SIZE; k++)
- if (swp->entries[k].val)
- swap_free(swp->entries[k]);
- swp = swp->next;
- }
-}
-
-/**
- * The swap_map_handle structure is used for handling the swap map in
+ * The swap_map_handle structure is used for handling swap in
* a file-alike way
*/
struct swap_map_handle {
struct swap_map_page *cur;
+ unsigned long cur_swap;
+ struct bitmap_page *bitmap;
unsigned int k;
};
-static inline void init_swap_map_handle(struct swap_map_handle *handle,
- struct swap_map_page *map)
+static void release_swap_writer(struct swap_map_handle *handle)
{
- handle->cur = map;
- handle->k = 0;
+ if (handle->cur)
+ free_page((unsigned long)handle->cur);
+ handle->cur = NULL;
+ if (handle->bitmap)
+ free_bitmap(handle->bitmap);
+ handle->bitmap = NULL;
}
-static inline int swap_map_write_page(struct swap_map_handle *handle,
- unsigned long addr)
+static int get_swap_writer(struct swap_map_handle *handle)
+{
+ handle->cur = (struct swap_map_page *)get_zeroed_page(GFP_KERNEL);
+ if (!handle->cur)
+ return -ENOMEM;
+ handle->bitmap = alloc_bitmap(count_swap_pages(root_swap, 0));
+ if (!handle->bitmap) {
+ release_swap_writer(handle);
+ return -ENOMEM;
+ }
+ handle->cur_swap = alloc_swap_page(root_swap, handle->bitmap);
+ if (!handle->cur_swap) {
+ release_swap_writer(handle);
+ return -ENOSPC;
+ }
+ handle->k = 0;
+ return 0;
+}
+
+static int swap_write_page(struct swap_map_handle *handle, void *buf)
{
int error;
+ unsigned long offset;
- error = write_page(addr, handle->cur->entries + handle->k);
+ if (!handle->cur)
+ return -EINVAL;
+ offset = alloc_swap_page(root_swap, handle->bitmap);
+ error = write_page(buf, offset);
if (error)
return error;
- if (++handle->k >= MAP_PAGE_SIZE) {
- handle->cur = handle->cur->next;
+ handle->cur->entries[handle->k++] = offset;
+ if (handle->k >= MAP_PAGE_ENTRIES) {
+ offset = alloc_swap_page(root_swap, handle->bitmap);
+ if (!offset)
+ return -ENOSPC;
+ handle->cur->next_swap = offset;
+ error = write_page(handle->cur, handle->cur_swap);
+ if (error)
+ return error;
+ memset(handle->cur, 0, PAGE_SIZE);
+ handle->cur_swap = offset;
handle->k = 0;
}
return 0;
}
+static int flush_swap_writer(struct swap_map_handle *handle)
+{
+ if (handle->cur && handle->cur_swap)
+ return write_page(handle->cur, handle->cur_swap);
+ else
+ return -EINVAL;
+}
+
/**
- * save_image_data - save the data pages pointed to by the PBEs
- * from the list @pblist using the swap map handle @handle
- * (assume there are @nr_pages data pages to save)
+ * save_image - save the suspend image data
*/
-static int save_image_data(struct pbe *pblist,
- struct swap_map_handle *handle,
- unsigned int nr_pages)
+static int save_image(struct swap_map_handle *handle,
+ struct snapshot_handle *snapshot,
+ unsigned int nr_pages)
{
unsigned int m;
- struct pbe *p;
+ int ret;
int error = 0;
printk("Saving image data pages (%u pages) ... ", nr_pages);
@@ -385,98 +391,22 @@
if (!m)
m = 1;
nr_pages = 0;
- for_each_pbe (p, pblist) {
- error = swap_map_write_page(handle, p->address);
- if (error)
- break;
- if (!(nr_pages % m))
- printk("\b\b\b\b%3d%%", nr_pages / m);
- nr_pages++;
- }
+ do {
+ ret = snapshot_read_next(snapshot, PAGE_SIZE);
+ if (ret > 0) {
+ error = swap_write_page(handle, data_of(*snapshot));
+ if (error)
+ break;
+ if (!(nr_pages % m))
+ printk("\b\b\b\b%3d%%", nr_pages / m);
+ nr_pages++;
+ }
+ } while (ret > 0);
if (!error)
printk("\b\b\b\bdone\n");
return error;
}
-static void dump_info(void)
-{
- pr_debug(" swsusp: Version: %u\n",swsusp_info.version_code);
- pr_debug(" swsusp: Num Pages: %ld\n",swsusp_info.num_physpages);
- pr_debug(" swsusp: UTS Sys: %s\n",swsusp_info.uts.sysname);
- pr_debug(" swsusp: UTS Node: %s\n",swsusp_info.uts.nodename);
- pr_debug(" swsusp: UTS Release: %s\n",swsusp_info.uts.release);
- pr_debug(" swsusp: UTS Version: %s\n",swsusp_info.uts.version);
- pr_debug(" swsusp: UTS Machine: %s\n",swsusp_info.uts.machine);
- pr_debug(" swsusp: UTS Domain: %s\n",swsusp_info.uts.domainname);
- pr_debug(" swsusp: CPUs: %d\n",swsusp_info.cpus);
- pr_debug(" swsusp: Image: %ld Pages\n",swsusp_info.image_pages);
- pr_debug(" swsusp: Total: %ld Pages\n", swsusp_info.pages);
-}
-
-static void init_header(unsigned int nr_pages)
-{
- memset(&swsusp_info, 0, sizeof(swsusp_info));
- swsusp_info.version_code = LINUX_VERSION_CODE;
- swsusp_info.num_physpages = num_physpages;
- memcpy(&swsusp_info.uts, &system_utsname, sizeof(system_utsname));
-
- swsusp_info.cpus = num_online_cpus();
- swsusp_info.image_pages = nr_pages;
- swsusp_info.pages = nr_pages +
- ((nr_pages * sizeof(long) + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
-}
-
-/**
- * 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;
-}
-
-/**
- * save_image_metadata - save the .orig_address fields of the PBEs
- * from the list @pblist using the swap map handle @handle
- */
-
-static int save_image_metadata(struct pbe *pblist,
- struct swap_map_handle *handle)
-{
- unsigned long *buf;
- unsigned int n = 0;
- struct pbe *p;
- int error = 0;
-
- printk("Saving image metadata ... ");
- buf = (unsigned long *)get_zeroed_page(GFP_ATOMIC);
- if (!buf)
- return -ENOMEM;
- p = pblist;
- while (p) {
- p = pack_orig_addresses(buf, p);
- error = swap_map_write_page(handle, (unsigned long)buf);
- if (error)
- break;
- n++;
- }
- free_page((unsigned long)buf);
- if (!error)
- printk("done (%u pages saved)\n", n);
- return error;
-}
-
/**
* enough_swap - Make sure we have enough swap to save the image.
*
@@ -486,8 +416,7 @@
static int enough_swap(unsigned int nr_pages)
{
- unsigned int free_swap = swap_info[root_swap].pages -
- swap_info[root_swap].inuse_pages;
+ unsigned int free_swap = count_swap_pages(root_swap, 1);
pr_debug("swsusp: free swap pages: %u\n", free_swap);
return free_swap > (nr_pages + PAGES_FOR_IO +
@@ -503,57 +432,44 @@
* correctly, we'll mark system clean, anyway.)
*/
-int swsusp_write(struct pbe *pblist, unsigned int nr_pages)
+int swsusp_write(void)
{
- struct swap_map_page *swap_map;
struct swap_map_handle handle;
- swp_entry_t start;
+ struct snapshot_handle snapshot;
+ struct swsusp_info *header;
+ unsigned long start;
int error;
if ((error = swsusp_swap_check())) {
printk(KERN_ERR "swsusp: Cannot find swap device, try swapon -a.\n");
return error;
}
- if (!enough_swap(nr_pages)) {
+ memset(&snapshot, 0, sizeof(struct snapshot_handle));
+ error = snapshot_read_next(&snapshot, PAGE_SIZE);
+ if (error < PAGE_SIZE)
+ return error < 0 ? error : -EFAULT;
+ header = (struct swsusp_info *)data_of(snapshot);
+ if (!enough_swap(header->pages)) {
printk(KERN_ERR "swsusp: Not enough free swap\n");
return -ENOSPC;
}
-
- init_header(nr_pages);
- swap_map = alloc_swap_map(swsusp_info.pages);
- if (!swap_map)
- return -ENOMEM;
- init_swap_map_handle(&handle, swap_map);
-
- error = swap_map_write_page(&handle, (unsigned long)&swsusp_info);
+ error = get_swap_writer(&handle);
+ if (!error) {
+ start = handle.cur_swap;
+ error = swap_write_page(&handle, header);
+ }
if (!error)
- error = save_image_metadata(pblist, &handle);
- if (!error)
- error = save_image_data(pblist, &handle, nr_pages);
+ error = save_image(&handle, &snapshot, header->pages - 1);
+ if (!error) {
+ flush_swap_writer(&handle);
+ printk("S");
+ error = mark_swapfiles(swp_entry(root_swap, start));
+ printk("|\n");
+ }
if (error)
- goto Free_image_entries;
-
- swap_map = reverse_swap_map(swap_map);
- error = save_swap_map(swap_map, &start);
- if (error)
- goto Free_map_entries;
-
- dump_info();
- printk( "S" );
- error = mark_swapfiles(start);
- printk( "|\n" );
- if (error)
- goto Free_map_entries;
-
-Free_swap_map:
- free_swap_map(swap_map);
+ free_all_swap_pages(root_swap, handle.bitmap);
+ release_swap_writer(&handle);
return error;
-
-Free_map_entries:
- free_swap_map_entries(swap_map);
-Free_image_entries:
- free_image_entries(swap_map);
- goto Free_swap_map;
}
/**
@@ -663,45 +579,6 @@
return error;
}
-/**
- * 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 void mark_unsafe_pages(struct pbe *pblist)
-{
- struct zone *zone;
- unsigned long zone_pfn;
- struct pbe *p;
-
- if (!pblist) /* a sanity check */
- return;
-
- /* Clear page flags */
- for_each_zone (zone) {
- for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn)
- if (pfn_valid(zone_pfn + zone->zone_start_pfn))
- ClearPageNosaveFree(pfn_to_page(zone_pfn +
- zone->zone_start_pfn));
- }
-
- /* Mark orig addresses */
- for_each_pbe (p, pblist)
- SetPageNosaveFree(virt_to_page(p->orig_address));
-
-}
-
-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;
- }
-}
-
/*
* Using bio to read from swap.
* This code requires a bit more work than just using buffer heads
@@ -779,14 +656,14 @@
* in a file-alike way
*/
-static inline void release_swap_map_reader(struct swap_map_handle *handle)
+static void release_swap_reader(struct swap_map_handle *handle)
{
if (handle->cur)
free_page((unsigned long)handle->cur);
handle->cur = NULL;
}
-static inline int get_swap_map_reader(struct swap_map_handle *handle,
+static int get_swap_reader(struct swap_map_handle *handle,
swp_entry_t start)
{
int error;
@@ -798,149 +675,80 @@
return -ENOMEM;
error = bio_read_page(swp_offset(start), handle->cur);
if (error) {
- release_swap_map_reader(handle);
+ release_swap_reader(handle);
return error;
}
handle->k = 0;
return 0;
}
-static inline int swap_map_read_page(struct swap_map_handle *handle, void *buf)
+static int swap_read_page(struct swap_map_handle *handle, void *buf)
{
unsigned long offset;
int error;
if (!handle->cur)
return -EINVAL;
- offset = swp_offset(handle->cur->entries[handle->k]);
+ offset = handle->cur->entries[handle->k];
if (!offset)
- return -EINVAL;
+ return -EFAULT;
error = bio_read_page(offset, buf);
if (error)
return error;
- if (++handle->k >= MAP_PAGE_SIZE) {
+ if (++handle->k >= MAP_PAGE_ENTRIES) {
handle->k = 0;
- offset = swp_offset(handle->cur->next_swap);
+ offset = handle->cur->next_swap;
if (!offset)
- release_swap_map_reader(handle);
+ release_swap_reader(handle);
else
error = bio_read_page(offset, handle->cur);
}
return error;
}
-static int check_header(void)
-{
- char *reason = NULL;
-
- dump_info();
- if (swsusp_info.version_code != LINUX_VERSION_CODE)
- reason = "kernel version";
- if (swsusp_info.num_physpages != num_physpages)
- reason = "memory size";
- if (strcmp(swsusp_info.uts.sysname,system_utsname.sysname))
- reason = "system type";
- if (strcmp(swsusp_info.uts.release,system_utsname.release))
- reason = "kernel release";
- if (strcmp(swsusp_info.uts.version,system_utsname.version))
- reason = "version";
- if (strcmp(swsusp_info.uts.machine,system_utsname.machine))
- reason = "machine";
- if (reason) {
- printk(KERN_ERR "swsusp: Resume mismatch: %s\n", reason);
- return -EPERM;
- }
- return 0;
-}
-
/**
- * load_image_data - load the image data using the swap map handle
- * @handle and store them using the page backup list @pblist
+ * load_image - load the image using the swap map handle
+ * @handle and the snapshot handle @snapshot
* (assume there are @nr_pages pages to load)
*/
-static int load_image_data(struct pbe *pblist,
- struct swap_map_handle *handle,
- unsigned int nr_pages)
+static int load_image(struct swap_map_handle *handle,
+ struct snapshot_handle *snapshot,
+ unsigned int nr_pages)
{
- int error;
unsigned int m;
- struct pbe *p;
+ int ret;
+ int error = 0;
- if (!pblist)
- return -EINVAL;
printk("Loading image data pages (%u pages) ... ", nr_pages);
m = nr_pages / 100;
if (!m)
m = 1;
nr_pages = 0;
- p = pblist;
- while (p) {
- error = swap_map_read_page(handle, (void *)p->address);
- if (error)
- break;
- p = p->next;
- if (!(nr_pages % m))
- printk("\b\b\b\b%3d%%", nr_pages / m);
- nr_pages++;
- }
+ do {
+ ret = snapshot_write_next(snapshot, PAGE_SIZE);
+ if (ret > 0) {
+ error = swap_read_page(handle, data_of(*snapshot));
+ if (error)
+ break;
+ if (!(nr_pages % m))
+ printk("\b\b\b\b%3d%%", nr_pages / m);
+ nr_pages++;
+ }
+ } while (ret > 0);
if (!error)
printk("\b\b\b\bdone\n");
+ if (!snapshot_image_loaded(snapshot))
+ error = -ENODATA;
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;
-}
-
-/**
- * load_image_metadata - load the image metadata using the swap map
- * handle @handle and put them into the PBEs in the list @pblist
- */
-
-static int load_image_metadata(struct pbe *pblist, struct swap_map_handle *handle)
-{
- struct pbe *p;
- unsigned long *buf;
- unsigned int n = 0;
- int error = 0;
-
- printk("Loading image metadata ... ");
- buf = (unsigned long *)get_zeroed_page(GFP_ATOMIC);
- if (!buf)
- return -ENOMEM;
- p = pblist;
- while (p) {
- error = swap_map_read_page(handle, buf);
- if (error)
- break;
- p = unpack_orig_addresses(buf, p);
- n++;
- }
- free_page((unsigned long)buf);
- if (!error)
- printk("done (%u pages loaded)\n", n);
- return error;
-}
-
-int swsusp_read(struct pbe **pblist_ptr)
+int swsusp_read(void)
{
int error;
- struct pbe *p, *pblist;
struct swap_map_handle handle;
+ struct snapshot_handle snapshot;
+ struct swsusp_info *header;
unsigned int nr_pages;
if (IS_ERR(resume_bdev)) {
@@ -948,38 +756,19 @@
return PTR_ERR(resume_bdev);
}
- error = get_swap_map_reader(&handle, swsusp_header.image);
+ memset(&snapshot, 0, sizeof(struct snapshot_handle));
+ error = snapshot_write_next(&snapshot, PAGE_SIZE);
+ if (error < PAGE_SIZE)
+ return error < 0 ? error : -EFAULT;
+ header = (struct swsusp_info *)data_of(snapshot);
+ error = get_swap_reader(&handle, swsusp_header.image);
if (!error)
- error = swap_map_read_page(&handle, &swsusp_info);
- if (!error)
- error = check_header();
- if (error)
- return error;
- nr_pages = swsusp_info.image_pages;
- p = alloc_pagedir(nr_pages, GFP_ATOMIC, 0);
- if (!p)
- return -ENOMEM;
- error = load_image_metadata(p, &handle);
+ error = swap_read_page(&handle, header);
if (!error) {
- mark_unsafe_pages(p);
- pblist = alloc_pagedir(nr_pages, GFP_ATOMIC, 1);
- if (pblist)
- copy_page_backup_list(pblist, p);
- free_pagedir(p);
- if (!pblist)
- error = -ENOMEM;
-
- /* Allocate memory for the image and read the data from swap */
- if (!error)
- error = alloc_data_pages(pblist, GFP_ATOMIC, 1);
- if (!error) {
- release_eaten_pages();
- error = load_image_data(pblist, &handle, nr_pages);
- }
- if (!error)
- *pblist_ptr = pblist;
+ nr_pages = header->image_pages;
+ error = load_image(&handle, &snapshot, nr_pages);
}
- release_swap_map_reader(&handle);
+ release_swap_reader(&handle);
blkdev_put(resume_bdev);
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 365ed6f..4d11f9d 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -45,7 +45,7 @@
struct swap_list_t swap_list = {-1, -1};
-struct swap_info_struct swap_info[MAX_SWAPFILES];
+static struct swap_info_struct swap_info[MAX_SWAPFILES];
static DEFINE_MUTEX(swapon_mutex);
@@ -417,6 +417,59 @@
}
}
+#ifdef CONFIG_SOFTWARE_SUSPEND
+/*
+ * Find the swap type that corresponds to given device (if any)
+ *
+ * This is needed for software suspend and is done in such a way that inode
+ * aliasing is allowed.
+ */
+int swap_type_of(dev_t device)
+{
+ int i;
+
+ if (!device)
+ return -EINVAL;
+ spin_lock(&swap_lock);
+ for (i = 0; i < nr_swapfiles; i++) {
+ struct inode *inode;
+
+ if (!(swap_info[i].flags & SWP_WRITEOK))
+ continue;
+ inode = swap_info->swap_file->f_dentry->d_inode;
+ if (S_ISBLK(inode->i_mode) &&
+ device == MKDEV(imajor(inode), iminor(inode))) {
+ spin_unlock(&swap_lock);
+ return i;
+ }
+ }
+ spin_unlock(&swap_lock);
+ return -ENODEV;
+}
+
+/*
+ * Return either the total number of swap pages of given type, or the number
+ * of free pages of that type (depending on @free)
+ *
+ * This is needed for software suspend
+ */
+unsigned int count_swap_pages(int type, int free)
+{
+ unsigned int n = 0;
+
+ if (type < nr_swapfiles) {
+ spin_lock(&swap_lock);
+ if (swap_info[type].flags & SWP_WRITEOK) {
+ n = swap_info[type].pages;
+ if (free)
+ n -= swap_info[type].inuse_pages;
+ }
+ spin_unlock(&swap_lock);
+ }
+ return n;
+}
+#endif
+
/*
* No need to decide whether this PTE shares the swap entry with others,
* just let do_wp_page work it out if a write is requested later - to
