svn commit: r217828 - projects/graid/head/sys/geom/raid

[John Baldwin]

On Tuesday, January 25, 2011 11:33:03 am Alexander Motin wrote:
> On 25.01.2011 18:17, John Baldwin wrote:
> > On Tuesday, January 25, 2011 10:34:07 am Alexander Motin wrote:
> >> Author: mav
> >> Date: Tue Jan 25 15:34:07 2011
> >> New Revision: 217828
> >> URL: http://svn.freebsd.org/changeset/base/217828
> >>
> >> Log:
> >>    Implement kernel dumping to geom_raid volumes. Dumping mechanism supports
> >>    any RAID levels without any additional magic. Dumping to RAID0 and RAID1
> >>    verified to work right now.
> >>
> >> Modified:
> >>    projects/graid/head/sys/geom/raid/g_raid.c
> >>    projects/graid/head/sys/geom/raid/g_raid.h
> >>    projects/graid/head/sys/geom/raid/md_intel.c
> >>
> >> Modified: projects/graid/head/sys/geom/raid/g_raid.c
> >>
> > ==============================================================================
> >> --- projects/graid/head/sys/geom/raid/g_raid.c	Tue Jan 25 15:18:10 2011	
> > (r217827)
> >> +++ projects/graid/head/sys/geom/raid/g_raid.c	Tue Jan 25 15:34:07 2011	
> > (r217828)
> >> +static int
> >> +g_raid_dump(void *arg,
> >> +    void *virtual, vm_offset_t physical, off_t offset, size_t length)
> >> +{
> >> +	struct g_raid_softc *sc;
> >> +	struct g_raid_volume *vol;
> >> +	struct bio *bp;
> >> +
> >> +	vol = (struct g_raid_volume *)arg;
> >> +	sc = vol->v_softc;
> >> +	G_RAID_DEBUG(3, "Dumping at off %llu len %llu.",
> >> +	    (long long unsigned)offset, (long long unsigned)length);
> >> +
> >> +	bp = g_alloc_bio();
> >> +	bp->bio_cmd = BIO_WRITE;
> >> +	bp->bio_done = g_raid_dumpdone;
> >> +	bp->bio_attribute = NULL;
> >> +	bp->bio_offset = offset;
> >> +	bp->bio_length = length;
> >> +	bp->bio_data = virtual;
> >> +	bp->bio_to = vol->v_provider;
> >> +
> >> +	g_raid_start(bp);
> >> +
> >> +	while (!(bp->bio_flags&  BIO_DONE)) {
> >> +		G_RAID_DEBUG(4, "Poll...");
> >> +		g_raid_poll(sc);
> >> +		DELAY(10);
> >> +	}
> >> +
> >> +	G_RAID_DEBUG(3, "Dumping at off %llu len %llu done.",
> >> +	    (long long unsigned)offset, (long long unsigned)length);
> >> +
> >> +	g_destroy_bio(bp);
> >> +	return (0);
> >> +}
> >
> > Hmm, so this allocates bio's to make the dump work.  I believer other dump
> > routines in other drivers do not do this, but instead use pre-allocated
> > commands to schedule dump I/O requests.  Would it be possible to pre-allocate
> > the bio that is used here when dumping is enabled and reuse it for each
> > g_raid_dump() call without free'ing it when the I/O is finished?
> 
> Actually I've also thought about it. It is trivial to use static 
> variable in this particular place. But transformation modules 
> (RAID0/RAID1/...) are also allocating some BIOs via g_clone_bio() and 
> there it can be more difficult to fix, as several BIOs are allocated 
> same time to fulfill original request.

Hummm.  That's a bit unfortunate.

> When testing with minidump enabled I've noticed errors about attempts to 
> write after the dump device end. Is it unavoidable consequence of these 
> allocations?

Possibly.  That I can't say for certain.

-- 
John Baldwin