SELinux: use a helper function to determine seclabel

Use a helper to determine if a superblock should have the seclabel flag
rather than doing it in the function.  I'm going to use this in the
security server as well.

Signed-off-by: Eric Paris <eparis@redhat.com>

security/selinux/hooks.c

@@ -354,6 +354,29 @@ static int may_context_mount_inode_relabel(u32 sid,
 	return rc;
 }
 
+static int selinux_is_sblabel_mnt(struct super_block *sb)
+{
+	struct superblock_security_struct *sbsec = sb->s_security;
+
+	if (sbsec->behavior == SECURITY_FS_USE_XATTR ||
+	    sbsec->behavior == SECURITY_FS_USE_TRANS ||
+	    sbsec->behavior == SECURITY_FS_USE_TASK)
+		return 1;
+
+	/* Special handling for sysfs. Is genfs but also has setxattr handler*/
+	if (strncmp(sb->s_type->name, "sysfs", sizeof("sysfs")) == 0)
+		return 1;
+
+	/*
+	 * Special handling for rootfs. Is genfs but supports
+	 * setting SELinux context on in-core inodes.
+	 */
+	if (strncmp(sb->s_type->name, "rootfs", sizeof("rootfs")) == 0)
+		return 1;
+
+	return 0;
+}
+
 static int sb_finish_set_opts(struct super_block *sb)
 {
 	struct superblock_security_struct *sbsec = sb->s_security;
@@ -396,20 +419,7 @@ static int sb_finish_set_opts(struct super_block *sb)
 		       labeling_behaviors[sbsec->behavior-1]);
 
 	sbsec->flags |= SE_SBINITIALIZED;
-	if (sbsec->behavior == SECURITY_FS_USE_XATTR ||
-	    sbsec->behavior == SECURITY_FS_USE_TRANS ||
-	    sbsec->behavior == SECURITY_FS_USE_TASK)
-		sbsec->flags |= SBLABEL_MNT;
-
-	/* Special handling for sysfs. Is genfs but also has setxattr handler*/
-	if (strncmp(sb->s_type->name, "sysfs", sizeof("sysfs")) == 0)
-		sbsec->flags |= SBLABEL_MNT;
-
-	/*
-	 * Special handling for rootfs. Is genfs but supports
-	 * setting SELinux context on in-core inodes.
-	 */
-	if (strncmp(sb->s_type->name, "rootfs", sizeof("rootfs")) == 0)
+	if (selinux_is_sblabel_mnt(sb))
 		sbsec->flags |= SBLABEL_MNT;
 
 	/* Initialize the root inode. */