cvs commit: src/sys/fs/msdosfs msdosfs_vfsops.c

[Bruce Evans]

bde         2007-07-23 07:10:17 UTC

  FreeBSD src repository

  Modified files:
    sys/fs/msdosfs       msdosfs_vfsops.c 
  Log:
  Make using msdosfs as the root file system sort of work:
  
  o Initialize ownerships and permissions.  They were garbage (0) for
    root mounts since vfs_mountroot_try() doesn't ask for them to be set
    and msdosfs's old incomplete code to set them was removed.  The
    garbage happened to give the correct ownerships root:wheel, but it
    gave permissions 000 so init could not be execed.  Use the macros
    for root: wheel and 0755.  (The removed code gave 0:0 and 0777.  0755
    is more normal and secure, thought wrong for /tmp.)
  
  o Check the readonly flag for initial (non-MNT_UPDATE) mounts in the
    correct place, as in ffs.  For root mounts, it is only passed in
    mp->mnt_flags, since vfs_mountroot_try() only passes it as a flag
    and nothing translates the flag to the "ro" option string.  msdosfs
    only looked for it in the string, so it gave a rw mount for root
    mounts without even clearing the flag in mp->mnt_flags, so the final
    state was inconsistent.  Checking the flag only in mp->mnt_flags
    works for initial userland mounts too.  The MNT_UPDATE case is
    messier.
  
  The main point that should work but doesn't is fsck of msdosfs root
  while it is mounted ro.  This needs mainly MNT_RELOAD support to work.
  It should be possible to run fsck -p and succeed provided the fs is
  consistent, not just for msdosfs, but this fails because fsck -p always
  tries to open the device rw.  The hack that allows open for writing
  in ffs is not implemented in msdosfs, since without MNT_RELOAD support
  writing could only be harmful.  So fsck must be turned off to use
  msdosfs as root.  This is quite dangerous, since msdosfs is still missing
  actually using its fs-dirty flag internally, so it is happy to mount
  dirty fileystems rw.
  
  Unrelated changes:
  - Fix missing error handling for MNT_UPDATE from rw to ro.
  - Catch up with renaming msdos to msdosfs in a string.
  
  Approved by:    re (kensmith)
  
  Revision  Changes    Path
  1.167     +15 -3     src/sys/fs/msdosfs/msdosfs_vfsops.c