Btrfs: Add mount option to turn off data cow

A number of workloads do not require copy on write data or checksumming.
mount -o nodatasum to disable checksums and -o nodatacow to disable
both copy on write and checksumming.

In nodatacow mode, copy on write is still performed when a given extent
is under snapshot.

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

1 files changed, 8 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 5e255cabfd10..b51b021fff85 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -431,6 +431,7 @@ struct btrfs_root {
 #define BTRFS_STRING_ITEM_KEY   253
 
 #define BTRFS_MOUNT_NODATASUM           0x1
+#define BTRFS_MOUNT_NODATACOW           0x2
 
 #define btrfs_clear_opt(o, opt)         ((o) &= ~BTRFS_MOUNT_##opt)
 #define btrfs_set_opt(o, opt)           ((o) |= BTRFS_MOUNT_##opt)
@@ -915,6 +916,9 @@ static inline u32 btrfs_level_size(struct btrfs_root *root, int level) {
         btrfs_item_offset_nr(leaf, slot)))
 
 /* extent-tree.c */
+u32 btrfs_count_snapshots_in_path(struct btrfs_root *root,
+                                  struct btrfs_path *count_path,
+                                  u64 first_extent);
 int btrfs_extent_post_op(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root);
 int btrfs_copy_pinned(struct btrfs_root *root, struct extent_map_tree *copy);
@@ -974,6 +978,10 @@ int btrfs_cow_block(struct btrfs_trans_handle *trans,
                     struct btrfs_root *root, struct extent_buffer *buf,
                     struct extent_buffer *parent, int parent_slot,
                     struct extent_buffer **cow_ret);
+int btrfs_copy_root(struct btrfs_trans_handle *trans,
+                      struct btrfs_root *root,
+                      struct extent_buffer *buf,
+                      struct extent_buffer **cow_ret, u64 new_root_objectid);
 int btrfs_extend_item(struct btrfs_trans_handle *trans, struct btrfs_root
                       *root, struct btrfs_path *path, u32 data_size);
 int btrfs_truncate_item(struct btrfs_trans_handle *trans,