Date: Fri, 26 May 2006 08:02:57 -0600 From: Scott Long <scottl@samsco.org> To: Craig Rodrigues <rodrigc@crodrigues.org> Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/fs/udf udf_vfsops.c Message-ID: <44770A91.50007@samsco.org> In-Reply-To: <20060526033840.GA9864@crodrigues.org> References: <200605260121.k4Q1LqLd098354@repoman.freebsd.org> <44766E9B.6030000@samsco.org> <20060526033840.GA9864@crodrigues.org>
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Craig Rodrigues wrote:
> On Thu, May 25, 2006 at 08:57:31PM -0600, Scott Long wrote:
>
>>So is it no longer possible for a filesystem to veto or otherwise
>>massage an export request?
>
>
> It is still possible. This is because vfs_export() is
> only called in vfs_mount.c, only *after* the VFS_MOUNT()
> call for an individual filesystem is called.
>
> An individual filesystem can check the mount options being passed into
> its VFS_MOUNT() call, and do a vfs_getopt() and look for the
> "export" option, which contains a "struct export_args", which is
> eventually passed to vfs_export().
>
> The specific filesystem can do:
> (1) If the mount options passed into the specific filesystem's
> VFS_MOUNT() call contains "export", the filesystem
> can return an error from VFS_MOUNT() if it doesn't want to deal
> with export requests at all.
> The code in vfs_mount.c checks for the return status of VFS_MOUNT,
> and if there is an error, it will *not* call vfs_export().
>
> (2) If the mount options contains "export", the filesystem
> can do a vfs_getopt(), manipulate the contents of the struct export_args,
> then return 0 (for success). The code in VFS_MOUNT will
> then call vfs_export(), passing in the same struct export_args
> that the individual filesystem
>
>
> One example of a filesystem vetoing an "export" request
> is in fs/msdosfs/msdosfs_vfsops.c :
>
> if (vfs_flagopt(mp->mnt_optnew, "export", NULL, 0) {
> /* Process export requests. */
> if ((pmp->pm_flags & MSDOSFS_LARGEFS) != 0)
> return (EOPNOTSUPP);
> else
> return (0);
> }
>
>
> Most of the filesystem code I saw looked like they had
> just cut-n-pasted their calls to vfs_export(), so it was
> fairly easy to consolidate everything in one place, vfs_mount.c
>
> With my recent changes to mountd, to convert to nmount() and remove hardcoded
> dependencies on ufs, cd9660, ntfs, and msdosfs,
> it should be easier to export different filesystems from FreeBSD.
>
> For example, it should now be possible to NFS export an ext2fs
> from FreeBSD.
>
Assuming that fhtovp, vptofh, vget, and cookies all work in ext2fs =-)
Scott
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