Re: [PATCH v4 06/13] dm snapshot: merge target should not allocate new exceptions

Mike Snitzer
2009-11-20T20:54:15Z

On Fri, Nov 20 2009 at 3:27pm -0500,
Mike Snitzer <snitzer@redhat.com> 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