CRED: Wrap task credential accesses in the hugetlbfs 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: William Irwin <wli@holomorphy.com>
Signed-off-by: James Morris <jmorris@namei.org>

fs/hugetlbfs/inode.c

@@ -551,9 +551,9 @@ static int hugetlbfs_mknod(struct inode *dir,
 		if (S_ISDIR(mode))
 			mode |= S_ISGID;
 	} else {
-		gid = current->fsgid;
+		gid = current_fsgid();
 	}
-	inode = hugetlbfs_get_inode(dir->i_sb, current->fsuid, gid, mode, dev);
+	inode = hugetlbfs_get_inode(dir->i_sb, current_fsuid(), gid, mode, dev);
 	if (inode) {
 		dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 		d_instantiate(dentry, inode);
@@ -586,9 +586,9 @@ static int hugetlbfs_symlink(struct inode *dir,
 	if (dir->i_mode & S_ISGID)
 		gid = dir->i_gid;
 	else
-		gid = current->fsgid;
+		gid = current_fsgid();
 
-	inode = hugetlbfs_get_inode(dir->i_sb, current->fsuid,
+	inode = hugetlbfs_get_inode(dir->i_sb, current_fsuid(),
 					gid, S_IFLNK|S_IRWXUGO, 0);
 	if (inode) {
 		int l = strlen(symname)+1;
@@ -854,8 +854,8 @@ hugetlbfs_fill_super(struct super_block *sb, void *data, int silent)
 
 	config.nr_blocks = -1; /* No limit on size by default */
 	config.nr_inodes = -1; /* No limit on number of inodes by default */
-	config.uid = current->fsuid;
-	config.gid = current->fsgid;
+	config.uid = current_fsuid();
+	config.gid = current_fsgid();
 	config.mode = 0755;
 	config.hstate = &default_hstate;
 	ret = hugetlbfs_parse_options(data, &config);
@@ -970,8 +970,8 @@ struct file *hugetlb_file_setup(const char *name, size_t size)
 		goto out_shm_unlock;
 
 	error = -ENOSPC;
-	inode = hugetlbfs_get_inode(root->d_sb, current->fsuid,
-				current->fsgid, S_IFREG | S_IRWXUGO, 0);
+	inode = hugetlbfs_get_inode(root->d_sb, current_fsuid(),
+				current_fsgid(), S_IFREG | S_IRWXUGO, 0);
 	if (!inode)
 		goto out_dentry;