xattr: Add __vfs_{get,set,remove}xattr helpers

Right now, various places in the kernel check for the existence of
getxattr, setxattr, and removexattr inode operations and directly call
those operations.  Switch to helper functions and test for the IOP_XATTR
flag instead.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Acked-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 9c3437c..1f0c471 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -32,6 +32,7 @@
 #include <linux/file.h>
 #include <linux/scatterlist.h>
 #include <linux/slab.h>
+#include <linux/xattr.h>
 #include <asm/unaligned.h>
 #include "ecryptfs_kernel.h"
 
@@ -422,7 +423,7 @@
 	struct inode *lower_inode = d_inode(lower_dentry);
 	int rc;
 
-	if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
+	if (!(lower_inode->i_opflags & IOP_XATTR)) {
 		printk(KERN_WARNING
 		       "No support for setting xattr in lower filesystem\n");
 		rc = -ENOSYS;
@@ -436,15 +437,13 @@
 		goto out;
 	}
 	inode_lock(lower_inode);
-	size = lower_inode->i_op->getxattr(lower_dentry, lower_inode,
-					   ECRYPTFS_XATTR_NAME,
-					   xattr_virt, PAGE_SIZE);
+	size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
+			      xattr_virt, PAGE_SIZE);
 	if (size < 0)
 		size = 8;
 	put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
-	rc = lower_inode->i_op->setxattr(lower_dentry, lower_inode,
-					 ECRYPTFS_XATTR_NAME,
-					 xattr_virt, size, 0);
+	rc = __vfs_setxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
+			    xattr_virt, size, 0);
 	inode_unlock(lower_inode);
 	if (rc)
 		printk(KERN_ERR "Error whilst attempting to write inode size "