Btrfs: Fix csum error for compressed data

The decompress code doesn't take the logical offset in extent
pointer into account. If the logical offset isn't zero, data
will be decompressed into wrong pages.

The solution used here is to record the starting offset of the extent
in the file separately from the logical start of the extent_map struct.
This allows us to avoid problems inserting overlapping extents.

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

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h
index accfedaeb51..fb6eeef06bb 100644
--- a/fs/btrfs/extent_map.h
+++ b/fs/btrfs/extent_map.h
@@ -20,6 +20,7 @@ struct extent_map {
 	/* all of these are in bytes */
 	u64 start;
 	u64 len;
+	u64 orig_start;
 	u64 block_start;
 	u64 block_len;
 	unsigned long flags;