CRED: Wrap task credential accesses in the AFFS filesystem

Wrap access to task credentials so that they can be separated more easily from
the task_struct during the introduction of COW creds.

Change most current->(|e|s|fs)[ug]id to current_(|e|s|fs)[ug]id().

Change some task->e?[ug]id to task_e?[ug]id().  In some places it makes more
sense to use RCU directly rather than a convenient wrapper; these will be
addressed by later patches.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: James Morris <jmorris@namei.org>

fs/affs/inode.c

@@ -293,8 +293,8 @@ affs_new_inode(struct inode *dir)
 	mark_buffer_dirty_inode(bh, inode);
 	affs_brelse(bh);
 
-	inode->i_uid     = current->fsuid;
-	inode->i_gid     = current->fsgid;
+	inode->i_uid     = current_fsuid();
+	inode->i_gid     = current_fsgid();
 	inode->i_ino     = block;
 	inode->i_nlink   = 1;
 	inode->i_mtime   = inode->i_atime = inode->i_ctime = CURRENT_TIME_SEC;

fs/affs/super.c

@@ -163,8 +163,8 @@ parse_options(char *options, uid_t *uid, gid_t *gid, int *mode, int *reserved, s
 
 	/* Fill in defaults */
 
-	*uid        = current->uid;
-	*gid        = current->gid;
+	*uid        = current_uid();
+	*gid        = current_gid();
 	*reserved   = 2;
 	*root       = -1;
 	*blocksize  = -1;