The following commit has been merged in the linux branch: commit e244a0aeb6a599c19a7c802cda6e2d67c847b154 Author: Christoph Hellwig hch@lst.de Date: Wed Oct 14 09:24:59 2009 -0400

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

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index dfd7e6f..e5dd628 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -1153,6 +1153,7 @@ struct btrfs_root { #define BTRFS_MOUNT_FLUSHONCOMMIT (1 << 7) #define BTRFS_MOUNT_SSD_SPREAD (1 << 8) #define BTRFS_MOUNT_NOSSD (1 << 9) +#define BTRFS_MOUNT_DISCARD (1 << 10)

#define btrfs_clear_opt(o, opt) ((o) &= ~BTRFS_MOUNT_##opt) #define btrfs_set_opt(o, opt) ((o) |= BTRFS_MOUNT_##opt) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 4aedbff..bf7782f 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -1584,6 +1584,9 @@ static int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr, u64 map_length = num_bytes; struct btrfs_multi_bio *multi = NULL;

+ if (!btrfs_test_opt(root, DISCARD)) + return 0; + /* Tell the block device(s) that the sectors can be discarded */ ret = btrfs_map_block(&root->fs_info->mapping_tree, READ, bytenr, &map_length, &multi, 0); diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 3fbbf07..939b68f 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; }