kern/116608: [panic] [patch] [msdosfs] msdosfs fails to check mount options

Bruce Evans brde at
Sun Oct 14 23:18:20 PDT 2007

On Sun, 14 Oct 2007, Eugene Grosbein wrote:

> Subject: Re: kern/116608: [panic] [patch] [msdosfs] msdosfs fails to check mount options
> Here is a version of last patch adjusted for 7.0-PRERELEASE:

Is the bug in -current just that "mount -o rw" doesn't give rw when fstab
says ro?

ffs seems to have the same bug -- rw just doesn't work.  noro works.
This may be affected by my mount utilities being out of date (~5.2 mount,
~5.2 mount_ffs, old -current mount_msdosfs -- so old or broken that it
can't handle noauto in fstab).

Starting with a file system mounted ro, "mount -u -o fstab,rw" and
"mount -u -o current,rw" show the same bug (noro works).  Even
"mount -u" and "mount -u -o rw" don't work (noro works) for msdosfs,
but work for ffs.  This might be because my mount_msdosfs is old enough
to be missing fixes and my mount_ffs is old enough to be missing bugs
(it doesn't use nmount(), whose existence is the cause of most of these
bugs).  Upgrading to the ~5.2 mount_msdosfs fixes the bugs for -u but
not for initial mounts.  (I downgraded to the old -current mount_msdosfs
to test what it does.  This works because at least the compatibility cruft
parts of nmount() work OK.)

> --- sys/fs/msdosfs/msdosfs_vfsops.c.orig	2007-08-16 01:40:09.000000000 +0800
> +++ sys/fs/msdosfs/msdosfs_vfsops.c	2007-10-14 17:58:20.000000000 +0800
> @@ -265,6 +265,7 @@
>  			}
>  		}
>  		if (!(pmp->pm_flags & MSDOSFSMNT_RONLY) &&
> +		    !vfs_flagopt(mp->mnt_optnew, "noro", NULL, 0) &&
>  		    vfs_flagopt(mp->mnt_optnew, "ro", NULL, 0)) {
>  			error = VFS_SYNC(mp, MNT_WAIT, td);
>  			if (error)
> @@ -314,10 +315,12 @@
>  			ro_to_rw = 1;
>  		}
> +		if(!vfs_flagopt(mp->mnt_optnew, "noro", NULL, 0)) {
>  		vfs_flagopt(mp->mnt_optnew, "ro",
>  		    &pmp->pm_flags, MSDOSFSMNT_RONLY);
>  		vfs_flagopt(mp->mnt_optnew, "ro",
>  		    &mp->mnt_flag, MNT_RDONLY);
> +		}
>  		if (ro_to_rw) {
>  			/* Now that the volume is modifiable, mark it dirty. */

I think the patch belongs at a higher level.  Individual file systems
already have a lot of bloat to parse options.  Where mount(1) had
centralized table-driven option parsing for at least generic options,
ffs has a 4-line if statement for each supported option, and msdosfs
apparently has missing code -- why does ffs need more than a table to
indicate its support for the atime option, and how does atime work in
msdosfs where this support is missing; why does ffs have mounds of
code to parse both async and noasync, and if this is needed than why
isn't it needed for almost all options?


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