Btrfs: deal with bad mappings in btrfs_map_block

Martin Steigerwald reported a BUG_ON() in btrfs_map_block where we didn't find
a chunk for a particular block we were trying to map.  This happened because the
block was bogus.  We shouldn't be BUG_ON()'ing in this case, just print a
message and return an error.  This came from reada_add_block and it appears to
deal with an error fine so we should be good there.  Thanks,

Reported-by: Martin Steigerwald <Martin@lichtvoll.de>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 76ded9eb77a7..c8a315d4b86f 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4406,10 +4406,16 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
                 btrfs_crit(fs_info, "unable to find logical %llu len %llu",
                         (unsigned long long)logical,
                         (unsigned long long)*length);
-                BUG();
+                return -EINVAL;
+        }
+
+        if (em->start > logical || em->start + em->len < logical) {
+                btrfs_crit(fs_info, "found a bad mapping, wanted %Lu, "
+                           "found %Lu-%Lu\n", logical, em->start,
+                           em->start + em->len);
+                return -EINVAL;
         }
 
-        BUG_ON(em->start > logical || em->start + em->len < logical);
         map = (struct map_lookup *)em->bdev;
         offset = logical - em->start;