1 files changed, 25 insertions, 12 deletions

diff --git a/kernel/power/user.c b/kernel/power/user.c
index a8c96212bc1b..e819e17877ca 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -151,6 +151,7 @@ static ssize_t snapshot_read(struct file *filp, char __user *buf,
 {
         struct snapshot_data *data;
         ssize_t res;
+        loff_t pg_offp = *offp & ~PAGE_MASK;
 
         mutex_lock(&pm_mutex);
 
@@ -159,14 +160,19 @@ static ssize_t snapshot_read(struct file *filp, char __user *buf,
                 res = -ENODATA;
                 goto Unlock;
         }
-        res = snapshot_read_next(&data->handle, count);
-        if (res > 0) {
-                if (copy_to_user(buf, data_of(data->handle), res))
-                        res = -EFAULT;
-                else
-                        *offp = data->handle.offset;
+        if (!pg_offp) { /* on page boundary? */
+                res = snapshot_read_next(&data->handle);
+                if (res <= 0)
+                        goto Unlock;
+        } else {
+                res = PAGE_SIZE - pg_offp;
         }
 
+        res = simple_read_from_buffer(buf, count, &pg_offp,
+                        data_of(data->handle), res);
+        if (res > 0)
+                *offp += res;
+
  Unlock:
         mutex_unlock(&pm_mutex);
 
@@ -178,18 +184,25 @@ static ssize_t snapshot_write(struct file *filp, const char __user *buf,
 {
         struct snapshot_data *data;
         ssize_t res;
+        loff_t pg_offp = *offp & ~PAGE_MASK;
 
         mutex_lock(&pm_mutex);
 
         data = filp->private_data;
-        res = snapshot_write_next(&data->handle, count);
-        if (res > 0) {
-                if (copy_from_user(data_of(data->handle), buf, res))
-                        res = -EFAULT;
-                else
-                        *offp = data->handle.offset;
+
+        if (!pg_offp) {
+                res = snapshot_write_next(&data->handle);
+                if (res <= 0)
+                        goto unlock;
+        } else {
+                res = PAGE_SIZE - pg_offp;
         }
 
+        res = simple_write_to_buffer(data_of(data->handle), res, &pg_offp,
+                        buf, count);
+        if (res > 0)
+                *offp += res;
+unlock:
         mutex_unlock(&pm_mutex);
 
         return res;