Btrfs: Delete csum items when freeing extents

This finishes off the new checksumming code by removing csum items
for extents that are no longer in use.

The trick is doing it without racing because a single csum item may
hold csums for more than one extent.  Extra checks are added to
btrfs_csum_file_blocks to make sure that we are using the correct
csum item after dropping locks.

A new btrfs_split_item is added to split a single csum item so it
can be split without dropping the leaf lock.  This is used to
remove csum bytes from the middle of an item.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index f72b438..5b0c79d 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -409,6 +409,12 @@ struct btrfs_path {
 	int keep_locks;
 	int skip_locking;
 	int lowest_level;
+
+	/*
+	 * set by btrfs_split_item, tells search_slot to keep all locks
+	 * and to force calls to keep space in the nodes
+	 */
+	int search_for_split;
 };
 
 /*
@@ -1816,6 +1822,11 @@ int btrfs_truncate_item(struct btrfs_trans_handle *trans,
 			struct btrfs_root *root,
 			struct btrfs_path *path,
 			u32 new_size, int from_end);
+int btrfs_split_item(struct btrfs_trans_handle *trans,
+		     struct btrfs_root *root,
+		     struct btrfs_path *path,
+		     struct btrfs_key *new_key,
+		     unsigned long split_offset);
 int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
 		      *root, struct btrfs_key *key, struct btrfs_path *p, int
 		      ins_len, int cow);
@@ -1953,6 +1964,8 @@ int btrfs_lookup_inode(struct btrfs_trans_handle *trans, struct btrfs_root
 		       struct btrfs_key *location, int mod);
 
 /* file-item.c */
+int btrfs_del_csums(struct btrfs_trans_handle *trans,
+		    struct btrfs_root *root, u64 bytenr, u64 len);
 int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
 			  struct bio *bio, u32 *dst);
 int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,