From e244a0aeb6a599c19a7c802cda6e2d67c847b154 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 14 Oct 2009 09:24:59 -0400 Subject: 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 Signed-off-by: Chris Mason --- fs/btrfs/extent-tree.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'fs/btrfs/extent-tree.c') diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 4aedbff36b8f..bf7782fc5939 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); -- cgit v1.2.3 From 0634857488ec6e28fa22920cd0bee3c2ac07ccfd Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 14 Oct 2009 09:24:59 -0400 Subject: Btrfs: enable discard support The discard support code in btrfs currently is guarded by ifdefs for BIO_RW_DISCARD, which is never defines as it's the name of an enum memeber. Just remove the useless ifdefs to actually enable the code. Signed-off-by: Christoph Hellwig Signed-off-by: Chris Mason --- fs/btrfs/extent-tree.c | 6 ------ 1 file changed, 6 deletions(-) (limited to 'fs/btrfs/extent-tree.c') diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index bf7782fc5939..d4a35283d99e 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -1568,18 +1568,15 @@ static int remove_extent_backref(struct btrfs_trans_handle *trans, return ret; } -#ifdef BIO_RW_DISCARD static void btrfs_issue_discard(struct block_device *bdev, u64 start, u64 len) { blkdev_issue_discard(bdev, start >> 9, len >> 9, GFP_KERNEL); } -#endif static int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr, u64 num_bytes) { -#ifdef BIO_RW_DISCARD int ret; u64 map_length = num_bytes; struct btrfs_multi_bio *multi = NULL; @@ -1606,9 +1603,6 @@ static int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr, } return ret; -#else - return 0; -#endif } int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans, -- cgit v1.2.3 From 444528b3e614f7f2391488d9bca8e0b872db909b Mon Sep 17 00:00:00 2001 From: Chris Mason Date: Wed, 14 Oct 2009 09:38:28 -0400 Subject: Btrfs: always pin metadata in discard mode We have an optimization in btrfs to allow blocks to be immediately freed if they were allocated in this transaction and never written. Otherwise they are pinned and freed when the transaction commits. This isn't optimal for discard mode because immediately freeing them means immediately discarding them. It is better to give the block to the pinning code and letting the (slow) discard happen later. Signed-off-by: Chris Mason --- fs/btrfs/extent-tree.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'fs/btrfs/extent-tree.c') diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index d4a35283d99e..c56f91639dc1 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -3686,6 +3686,14 @@ static int pin_down_bytes(struct btrfs_trans_handle *trans, if (is_data) goto pinit; + /* + * discard is sloooow, and so triggering discards on + * individual btree blocks isn't a good plan. Just + * pin everything in discard mode. + */ + if (btrfs_test_opt(root, DISCARD)) + goto pinit; + buf = btrfs_find_tree_block(root, bytenr, num_bytes); if (!buf) goto pinit; -- cgit v1.2.3