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>

diff --git a/Documentation/filesystems/btrfs.txt b/Documentation/filesystems/btrfs.txt
index 79c08f368ace8d4f2545f0ad515913ab7dc2a007..bbd1f0f57ce9e409ad3d35008879ba36b58ab2d9 100644 (file)
--- a/Documentation/filesystems/btrfs.txt
+++ b/Documentation/filesystems/btrfs.txt
@@ -154,9 +154,10 @@ Options with (*) are default options and will not show in the mount options.
        (non-battery-backed) write-back cache, nobarrier option will lead to
        filesystem corruption on a system crash or power loss.
 
+  datacow(*)
   nodatacow
-       Disable data copy-on-write for newly created files.  Implies nodatasum,
-       and disables all compression.
+       Enable/disable data copy-on-write for newly created files.
+       Nodatacow implies nodatasum, and disables all compression.
 
   nodatasum
        Disable data checksumming for newly created files.

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 76eecd13db1939d03f13106e33e66a27549e25fa..6567865a25049c624ed9abdfbcc21f726e6783e0 100644 (file)
--- 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;