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, 0 insertions, 8 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 71bfe3a6a444..507081059d97 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1060,14 +1060,6 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
         last_index = (pos + count) >> PAGE_CACHE_SHIFT;
 
         /*
-         * if this is a nodatasum mount, force summing off for the inode
-         * all the time.  That way a later mount with summing on won't
-         * get confused
-         */
-        if (btrfs_test_opt(root, NODATASUM))
-                btrfs_set_flag(inode, NODATASUM);
-
-        /*
          * there are lots of better ways to do this, but this code
          * makes sure the first and last page in the file range are
          * up to date and ready for cow