[dm-devel] [PATCH] dm-snasphot: fix a crash if we have an origin with no snapshots

[Mikulas Patocka]

If we have an origin target with no snapshots, o->split_boundary is set to 0.
This causes BUG at block/bio.c:1474

This patch fixes the bug - if there are no snapshots, split_boundary is set
to 0x80000000U.

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
Cc: stable at vger.kernel.org
Reported-by: Michael Tokarev <mjt at tls.msk.ru>

Index: linux-2.6/drivers/md/dm-snap.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-snap.c
+++ linux-2.6/drivers/md/dm-snap.c
@@ -854,12 +854,11 @@ static int dm_add_exception(void *contex
 static uint32_t __minimum_chunk_size(struct origin *o)
 {
 	struct dm_snapshot *snap;
-	unsigned chunk_size = 0;
+	unsigned chunk_size = 0x80000000U;
 
 	if (o)
 		list_for_each_entry(snap, &o->snapshots, list)
-			chunk_size = min_not_zero(chunk_size,
-						  snap->store->chunk_size);
+			chunk_size = min(chunk_size, snap->store->chunk_size);
 
 	return (uint32_t) chunk_size;
 }