Reorder the flags field in struct btrfs_header and record a flag on writeout

This allows detection of blocks that have already been written in the
running transaction so they can be recowed instead of modified again.
It is step one in trusting the transid field of the block pointers.

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

1 files changed, 8 insertions, 2 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 70b6ddf..6ba5394 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -124,6 +124,7 @@ int btrfs_copy_root(struct btrfs_trans_handle *trans,
 	btrfs_set_header_bytenr(cow, cow->start);
 	btrfs_set_header_generation(cow, trans->transid);
 	btrfs_set_header_owner(cow, new_root_objectid);
+	btrfs_clear_header_flag(cow, BTRFS_HEADER_FLAG_WRITTEN);
 
 	WARN_ON(btrfs_header_generation(buf) > trans->transid);
 	ret = btrfs_inc_ref(trans, new_root, buf);
@@ -183,6 +184,7 @@ int __btrfs_cow_block(struct btrfs_trans_handle *trans,
 	btrfs_set_header_bytenr(cow, cow->start);
 	btrfs_set_header_generation(cow, trans->transid);
 	btrfs_set_header_owner(cow, root->root_key.objectid);
+	btrfs_clear_header_flag(cow, BTRFS_HEADER_FLAG_WRITTEN);
 
 	WARN_ON(btrfs_header_generation(buf) > trans->transid);
 	if (btrfs_header_generation(buf) != trans->transid) {
@@ -245,11 +247,14 @@ int btrfs_cow_block(struct btrfs_trans_handle *trans,
 	}
 
 	header_trans = btrfs_header_generation(buf);
-	if (header_trans == trans->transid) {
+	spin_lock(&root->fs_info->hash_lock);
+	if (header_trans == trans->transid &&
+	    !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN)) {
 		*cow_ret = buf;
+		spin_unlock(&root->fs_info->hash_lock);
 		return 0;
 	}
-
+	spin_unlock(&root->fs_info->hash_lock);
 	search_start = buf->start & ~((u64)(1024 * 1024 * 1024) - 1);
 	ret = __btrfs_cow_block(trans, root, buf, parent,
 				 parent_slot, cow_ret, search_start, 0);
@@ -1494,6 +1499,7 @@ static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
 	btrfs_set_header_bytenr(split, split->start);
 	btrfs_set_header_generation(split, trans->transid);
 	btrfs_set_header_owner(split, root->root_key.objectid);
+	btrfs_set_header_flags(split, 0);
 	write_extent_buffer(split, root->fs_info->fsid,
 			    (unsigned long)btrfs_header_fsid(split),
 			    BTRFS_FSID_SIZE);