freebsd-skq/sys/ufs
phk d9d9558b8b Move UFS from DEVFS backing to GEOM backing.
This eliminates a bunch of vnode overhead (approx 1-2 % speed
improvement) and gives us more control over the access to the storage
device.

Access counts on the underlying device are not correctly tracked and
therefore it is possible to read-only mount the same disk device multiple
times:
	syv# mount -p
	/dev/md0        /var    ufs rw  2 2
	/dev/ad0        /mnt    ufs ro  1 1
	/dev/ad0        /mnt2   ufs ro  1 1
	/dev/ad0        /mnt3   ufs ro  1 1

Since UFS/FFS is not a synchrousely consistent filesystem (ie: it caches
things in RAM) this is not possible with read-write mounts, and the system
will correctly reject this.

Details:

	Add a geom consumer and a bufobj pointer to ufsmount.

	Eliminate the vnode argument from softdep_disk_prewrite().
	Pick the vnode out of bp->b_vp for now.  Eventually we
	should find it through bp->b_bufobj->b_private.

	In the mountcode, use g_vfs_open() once we have used
	VOP_ACCESS() to check permissions.

	When upgrading and downgrading between r/o and r/w do the
	right thing with GEOM access counts.  Remove all the
	workarounds for not being able to do this with VOP_OPEN().

	If we are the root mount, drop the exclusive access count
	until we upgrade to r/w.  This allows fsck of the root
	filesystem and the MNT_RELOAD to work correctly.

	Set bo_private to the GEOM consumer on the device bufobj.

	Change the ffs_ops->strategy function to call g_vfs_strategy()

	In ufs_strategy() directly call the strategy on the disk
	bufobj.  Same in rawread.

	In ffs_fsync() we will no longer see VCHR device nodes, so
	remove code which synced the filesystem mounted on it, in
	case we came there.  I'm not sure this code made sense in
	the first place since we would have taken the specfs route
	on such a vnode.

	Redo the highly bogus readblock() function in the snapshot
	code to something slightly less bogus: Constructing an uio
	and using physio was really quite a detour.  Instead just
	fill in a bio and ship it down.
2004-10-29 10:15:56 +00:00
..
ffs Move UFS from DEVFS backing to GEOM backing. 2004-10-29 10:15:56 +00:00
ufs Move UFS from DEVFS backing to GEOM backing. 2004-10-29 10:15:56 +00:00