CRED: Wrap task credential accesses in 9P2000 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>
Reviewed-by: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Ron Minnich <rminnich@sandia.gov>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Cc: v9fs-developer@lists.sourceforge.net
Signed-off-by: James Morris <jmorris@namei.org>

fs/9p/fid.c

@@ -120,7 +120,7 @@ struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
 	switch (access) {
 	case V9FS_ACCESS_SINGLE:
 	case V9FS_ACCESS_USER:
-		uid = current->fsuid;
+		uid = current_fsuid();
 		any = 0;
 		break;
 

fs/9p/vfs_inode.c

@@ -215,8 +215,8 @@ struct inode *v9fs_get_inode(struct super_block *sb, int mode)
 	inode = new_inode(sb);
 	if (inode) {
 		inode->i_mode = mode;
-		inode->i_uid = current->fsuid;
-		inode->i_gid = current->fsgid;
+		inode->i_uid = current_fsuid();
+		inode->i_gid = current_fsgid();
 		inode->i_blocks = 0;
 		inode->i_rdev = 0;
 		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;

fs/9p/vfs_super.c

@@ -113,8 +113,8 @@ static int v9fs_get_sb(struct file_system_type *fs_type, int flags,
 	struct v9fs_session_info *v9ses = NULL;
 	struct p9_wstat *st = NULL;
 	int mode = S_IRWXUGO | S_ISVTX;
-	uid_t uid = current->fsuid;
-	gid_t gid = current->fsgid;
+	uid_t uid = current_fsuid();
+	gid_t gid = current_fsgid();
 	struct p9_fid *fid;
 	int retval = 0;
 

net/9p/client.c

@@ -628,7 +628,7 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
 	memset(&fid->qid, 0, sizeof(struct p9_qid));
 	fid->mode = -1;
 	fid->rdir_fpos = 0;
-	fid->uid = current->fsuid;
+	fid->uid = current_fsuid();
 	fid->clnt = clnt;
 	fid->aux = NULL;