btrfs: Add datacow mount option.

Add datacow mount option to enable copy-on-write with
remount option.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 76eecd13db19..6567865a2504 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -324,7 +324,7 @@ enum {
         Opt_check_integrity, Opt_check_integrity_including_extent_data,
         Opt_check_integrity_print_mask, Opt_fatal_errors, Opt_rescan_uuid_tree,
         Opt_commit_interval, Opt_barrier, Opt_nodefrag, Opt_nodiscard,
-        Opt_noenospc_debug, Opt_noflushoncommit, Opt_acl,
+        Opt_noenospc_debug, Opt_noflushoncommit, Opt_acl, Opt_datacow,
         Opt_err,
 };
 
@@ -335,6 +335,7 @@ static match_table_t tokens = {
         {Opt_device, "device=%s"},
         {Opt_nodatasum, "nodatasum"},
         {Opt_nodatacow, "nodatacow"},
+        {Opt_datacow, "datacow"},
         {Opt_nobarrier, "nobarrier"},
         {Opt_barrier, "barrier"},
         {Opt_max_inline, "max_inline=%s"},
@@ -446,6 +447,11 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
                         btrfs_set_opt(info->mount_opt, NODATACOW);
                         btrfs_set_opt(info->mount_opt, NODATASUM);
                         break;
+                case Opt_datacow:
+                        if (btrfs_test_opt(root, NODATACOW))
+                                btrfs_info(root->fs_info, "setting datacow");
+                        btrfs_clear_opt(info->mount_opt, NODATACOW);
+                        break;
                 case Opt_compress_force:
                 case Opt_compress_force_type:
                         compress_force = true;