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, 2 insertions, 0 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 337221e..85841c5 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -222,6 +222,7 @@ int btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end,
 		    em->start < start) {
 			split->start = em->start;
 			split->len = start - em->start;
+			split->orig_start = em->orig_start;
 			split->block_start = em->block_start;
 
 			if (compressed)
@@ -243,6 +244,7 @@ int btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end,
 
 			split->start = start + len;
 			split->len = em->start + em->len - (start + len);
+			split->orig_start = em->orig_start;
 			split->bdev = em->bdev;
 			split->flags = flags;