[dm-devel] [PATCH] device-mapper snaphot: barriers not supported
Alasdair G Kergon
agk at redhat.com
Wed Jan 11 15:04:26 UTC 2006
The snapshot and origin targets are incapable of handling barriers and
need to indicate this.
http://www.kernel.org/pub/linux/kernel/people/agk/patches/2.6/editing/dm-snapshot-barriers-not-supported.patch
Index: linux-2.6.14-rc2/drivers/md/dm-snap.c
===================================================================
--- linux-2.6.14-rc2.orig/drivers/md/dm-snap.c 2006-01-06 14:27:50.000000000 +0000
+++ linux-2.6.14-rc2/drivers/md/dm-snap.c 2006-01-06 14:36:26.000000000 +0000
@@ -799,6 +799,9 @@ static int snapshot_map(struct dm_target
if (!s->valid)
return -EIO;
+ if (unlikely(bio_barrier(bio)))
+ return -EOPNOTSUPP;
+
/*
* Write to snapshot - higher level takes care of RW/RO
* flags so we should only get this if we are
@@ -1065,6 +1068,9 @@ static int origin_map(struct dm_target *
struct dm_dev *dev = (struct dm_dev *) ti->private;
bio->bi_bdev = dev->bdev;
+ if (unlikely(bio_barrier(bio)))
+ return -EOPNOTSUPP;
+
/* Only tell snapshots if this is a write */
return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : 1;
}
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