eCryptfs: update metadata read/write functions

Update the metadata read/write functions and grow_file() to use the
read_write.c routines.  Do not open another lower file; use the persistent
lower file instead.  Provide a separate function for
crypto.c::ecryptfs_read_xattr_region() to get to the lower xattr without
having to go through the eCryptfs getxattr.

Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c
index 59c846d..df70bfa 100644
--- a/fs/ecryptfs/file.c
+++ b/fs/ecryptfs/file.c
@@ -248,7 +248,7 @@
 	mutex_lock(&crypt_stat->cs_mutex);
 	if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED)
 	    || !(crypt_stat->flags & ECRYPTFS_KEY_VALID)) {
-		rc = ecryptfs_read_metadata(ecryptfs_dentry, lower_file);
+		rc = ecryptfs_read_metadata(ecryptfs_dentry);
 		if (rc) {
 			ecryptfs_printk(KERN_DEBUG,
 					"Valid headers not found\n");