Btrfs: add -o discard option

Enable discard by default is not a good idea given the the trim speed
of SSD prototypes we've seen, and the carecteristics for many high-end
arrays.  Turn of discards by default and require the -o discard option
to enable them on.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 3fbbf0761ac2..939b68f0612d 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -66,7 +66,8 @@ enum {
         Opt_degraded, Opt_subvol, Opt_device, Opt_nodatasum, Opt_nodatacow,
         Opt_max_extent, Opt_max_inline, Opt_alloc_start, Opt_nobarrier,
         Opt_ssd, Opt_nossd, Opt_ssd_spread, Opt_thread_pool, Opt_noacl,
-        Opt_compress, Opt_notreelog, Opt_ratio, Opt_flushoncommit, Opt_err,
+        Opt_compress, Opt_notreelog, Opt_ratio, Opt_flushoncommit,
+        Opt_discard, Opt_err,
 };
 
 static match_table_t tokens = {
@@ -88,6 +89,7 @@ static match_table_t tokens = {
         {Opt_notreelog, "notreelog"},
         {Opt_flushoncommit, "flushoncommit"},
         {Opt_ratio, "metadata_ratio=%d"},
+        {Opt_discard, "discard"},
         {Opt_err, NULL},
 };
 
@@ -257,6 +259,9 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
                                        info->metadata_ratio);
                         }
                         break;
+                case Opt_discard:
+                        btrfs_set_opt(info->mount_opt, DISCARD);
+                        break;
                 default:
                         break;
                 }