btrfs: Add noflushoncommit mount option.

Add noflushoncommit mount option to disable flush on commit 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>

2 files changed, 8 insertions, 1 deletions

diff --git a/Documentation/filesystems/btrfs.txt b/Documentation/filesystems/btrfs.txt
index 13a7cac80430..303b49c6c296 100644
--- a/Documentation/filesystems/btrfs.txt
+++ b/Documentation/filesystems/btrfs.txt
@@ -117,6 +117,7 @@ Options with (*) are default options and will not show in the mount options.
           "bug" - BUG() on a fatal error.  This is the default.
           "panic" - panic() on a fatal error.
 
+  noflushoncommit(*)
   flushoncommit
         The 'flushoncommit' mount option forces any data dirtied by a write in a
         prior transaction to commit as part of the current commit.  This makes
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 832540645c20..98a682340935 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_noenospc_debug, Opt_noflushoncommit,
         Opt_err,
 };
 
@@ -350,6 +350,7 @@ static match_table_t tokens = {
         {Opt_noacl, "noacl"},
         {Opt_notreelog, "notreelog"},
         {Opt_flushoncommit, "flushoncommit"},
+        {Opt_noflushoncommit, "noflushoncommit"},
         {Opt_ratio, "metadata_ratio=%d"},
         {Opt_discard, "discard"},
         {Opt_nodiscard, "nodiscard"},
@@ -562,6 +563,11 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
                         btrfs_info(root->fs_info, "turning on flush-on-commit");
                         btrfs_set_opt(info->mount_opt, FLUSHONCOMMIT);
                         break;
+                case Opt_noflushoncommit:
+                        if (btrfs_test_opt(root, FLUSHONCOMMIT))
+                                btrfs_info(root->fs_info, "turning off flush-on-commit");
+                        btrfs_clear_opt(info->mount_opt, FLUSHONCOMMIT);
+                        break;
                 case Opt_ratio:
                         ret = match_int(&args[0], &intarg);
                         if (ret) {