nfs: fix xattr inode op pointers when disabled

Chris Mason reported a NULL pointer derefernence in generic_getxattr()
that was due to sb->s_xattr being NULL.

The reason is that the nfs #ifdef's for ACL support were misplaced, and
the nfs3 inode operations had the xattr operation pointers set up, even
though xattrs were not actually supported.  As a result, the xattr code
was being called without the infrastructure having been set up.

Move the #ifdef's appropriately.
Reported-and-tested-by: NChris Mason <clm@fb.com>
Acked-by: Al Viro viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/nfs/nfs3proc.c

@@ -924,11 +924,11 @@ static const struct inode_operations nfs3_dir_inode_operations = {
 	.permission	= nfs_permission,
 	.getattr	= nfs_getattr,
 	.setattr	= nfs_setattr,
+#ifdef CONFIG_NFS_V3_ACL
 	.listxattr	= generic_listxattr,
 	.getxattr	= generic_getxattr,
 	.setxattr	= generic_setxattr,
 	.removexattr	= generic_removexattr,
-#ifdef CONFIG_NFS_V3_ACL
 	.get_acl	= nfs3_get_acl,
 	.set_acl	= nfs3_set_acl,
 #endif
@@ -938,11 +938,11 @@ static const struct inode_operations nfs3_file_inode_operations = {
 	.permission	= nfs_permission,
 	.getattr	= nfs_getattr,
 	.setattr	= nfs_setattr,
+#ifdef CONFIG_NFS_V3_ACL
 	.listxattr	= generic_listxattr,
 	.getxattr	= generic_getxattr,
 	.setxattr	= generic_setxattr,
 	.removexattr	= generic_removexattr,
-#ifdef CONFIG_NFS_V3_ACL
 	.get_acl	= nfs3_get_acl,
 	.set_acl	= nfs3_set_acl,
 #endif