On Fri, 20 Nov 2009, Mike Snitzer wrote:
> On Fri, Nov 20 2009 at 3:27pm -0500,
> Mike Snitzer <snitzer@xxxxxxxxxx> wrote:
>
> > If a write request to a merging snapshot device is to be dispatched
> > directly to the origin (because the chunk is not remapped or was already
> > merged), snapshot_merge_map() must make exceptions in other snapshots.
> ...
> > +static int snapshot_merge_map(struct dm_target *ti, struct bio *bio,
> > + union map_info *map_context)
> > +{
> > + struct dm_exception *e;
> > + struct dm_snapshot *s = ti->private;
> > + int r = DM_MAPIO_REMAPPED;
> > + chunk_t chunk;
> > +
> > + chunk = sector_to_chunk(s->store, bio->bi_sector);
> > +
> > + down_read(&s->lock);
> > +
> > + /* Full snapshots are not usable */
> > + if (!s->valid) {
> > + r = -EIO;
> > + goto out_unlock;
> > + }
> > +
> > + /* If the block is already remapped - use that */
> > + e = dm_lookup_exception(&s->complete, chunk);
> > + if (e) {
> > + remap_exception(s, e, bio, chunk);
> > + goto out_unlock;
> > + }
> > +
> > + bio->bi_bdev = s->origin->bdev;
> > +
> > + if (bio_rw(bio) == WRITE) {
> > + up_write(&s->lock);
> > + return do_origin(s->origin, bio);
> > + }
>
> OK, I caught this in review but clearly didn't refresh the patch; the
> above up_write() should be up_read().
>
> Mike
Right.
BTW, this will be converted to a single lock (non-read-write) anyway, when
those clustering patches will be applied.
Mikulas
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