2 files changed, 22 insertions, 1 deletions

diff --git a/fs/libfs.c b/fs/libfs.c
index b004dfadd891..892d41cb3382 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -528,6 +528,23 @@ ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
         return count;
 }
 
+ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
+                                const void *from, size_t available)
+{
+        loff_t pos = *ppos;
+
+        if (pos < 0)
+                return -EINVAL;
+        if (pos >= available)
+                return 0;
+        if (count > available - pos)
+                count = available - pos;
+        memcpy(to, from + pos, count);
+        *ppos = pos + count;
+
+        return count;
+}
+
 /*
  * Transaction based IO.
  * The file expects a single write which triggers the transaction, and then
@@ -800,6 +817,7 @@ EXPORT_SYMBOL(simple_statfs);
 EXPORT_SYMBOL(simple_sync_file);
 EXPORT_SYMBOL(simple_unlink);
 EXPORT_SYMBOL(simple_read_from_buffer);
+EXPORT_SYMBOL(memory_read_from_buffer);
 EXPORT_SYMBOL(simple_transaction_get);
 EXPORT_SYMBOL(simple_transaction_read);
 EXPORT_SYMBOL(simple_transaction_release);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f413085f748e..d490779f18d9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2000,7 +2000,10 @@ extern int simple_fill_super(struct super_block *, int, struct tree_descr *);
 extern int simple_pin_fs(struct file_system_type *, struct vfsmount **mount, int *count);
 extern void simple_release_fs(struct vfsmount **mount, int *count);
 
-extern ssize_t simple_read_from_buffer(void __user *, size_t, loff_t *, const void *, size_t);
+extern ssize_t simple_read_from_buffer(void __user *to, size_t count,
+                        loff_t *ppos, const void *from, size_t available);
+extern ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
+                        const void *from, size_t available);
 
 #ifdef CONFIG_MIGRATION
 extern int buffer_migrate_page(struct address_space *,