Panic in getblkx() booting from disc1.iso in Qemu VM

[Kirk McKusick]

Thanks Rebecca for the report and Mark for the analysis of the problem.
This should be fixed in -r342290.

	Kirk McKusick

=-=-=

From:    Kirk McKusick <mckusick at FreeBSD.org>
Date:    Fri, 21 Dec 2018 01:09:25 +0000 (UTC)
To:      src-committers at freebsd.org, svn-src-all at freebsd.org,
	 svn-src-head at freebsd.org
Subject: svn commit: r342290 - head/sys/kern

Author: mckusick
Date: Fri Dec 21 01:09:25 2018
New Revision: 342290
URL: https://svnweb.freebsd.org/changeset/base/342290

Log:
  Some filesystems (like cd9660 and ext3) require that VFS_STATFS()
  be called before VFS_ROOT() is called. Move the call for VFS_STATFS()
  so that it is done after VFS_MOUNT(), but before VFS_ROOT().
  This change actually improves the robustness of the mount system
  call because it returns an error rather than failing silently
  when VFS_STATFS() returns failure.
  
  Reported by:  Rebecca Cran <rebecca at bluestop.org>
  Sponsored by: Netflix

Modified:
  head/sys/kern/vfs_mount.c

Modified: head/sys/kern/vfs_mount.c
==============================================================================
--- head/sys/kern/vfs_mount.c	Thu Dec 20 22:39:58 2018	(r342289)
+++ head/sys/kern/vfs_mount.c	Fri Dec 21 01:09:25 2018	(r342290)
@@ -895,6 +895,7 @@ vfs_domount_first(
 	 */
 	error1 = 0;
 	if ((error = VFS_MOUNT(mp)) != 0 ||
+	    (error1 = VFS_STATFS(mp, &mp->mnt_stat)) != 0 ||
 	    (error1 = VFS_ROOT(mp, LK_EXCLUSIVE, &newdp)) != 0) {
 		if (error1 != 0) {
 			error = error1;
@@ -916,7 +917,6 @@ vfs_domount_first(
 		vfs_freeopts(mp->mnt_opt);
 	mp->mnt_opt = mp->mnt_optnew;
 	*optlist = NULL;
-	(void)VFS_STATFS(mp, &mp->mnt_stat);
 
 	/*
 	 * Prevent external consumers of mount options from reading mnt_optnew.