Btrfs: fix nodatasum handling in balancing code

Checksums on data can be disabled by mount option, so it's
possible some data extents don't have checksums or have
invalid checksums. This causes trouble for data relocation.
This patch contains following things to make data relocation
work.

1) make nodatasum/nodatacow mount option only affects new
files. Checksums and COW on data are only controlled by the
inode flags.

2) check the existence of checksum in the nodatacow checker.
If checksums exist, force COW the data extent. This ensure that
checksum for a given block is either valid or does not exist.

3) update data relocation code to properly handle the case
of checksum missing.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 2d5f67065b69..c5b483a79137 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -16,6 +16,7 @@
 #define EXTENT_ORDERED (1 << 9)
 #define EXTENT_ORDERED_METADATA (1 << 10)
 #define EXTENT_BOUNDARY (1 << 11)
+#define EXTENT_NODATASUM (1 << 12)
 #define EXTENT_IOBITS (EXTENT_LOCKED | EXTENT_WRITEBACK)
 
 /* flags for bio submission */