From f66e0209bd914465c277c259472aa974cad94e3f Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Thu, 28 Sep 2023 11:12:49 +0100 Subject: btrfs: stop reserving excessive space for block group item updates Space for block group item updates, necessary after allocating or deallocating an extent from a block group, is reserved in the delayed refs block reserve. Currently we do this by incrementing the transaction handle's delayed_ref_updates counter and then calling btrfs_update_delayed_refs_rsv(), which will increase the size of the delayed refs block reserve by an amount that corresponds to the same amount we use for delayed refs, given by btrfs_calc_delayed_ref_bytes(). That is an excessive amount because it corresponds to the amount of space needed to insert one item in a btree (btrfs_calc_insert_metadata_size()) times 2 when the free space tree feature is enabled. All we need is an amount as given by btrfs_calc_metadata_size(), since we only need to update an existing block group item in the extent tree (or block group tree if this feature is enabled). By using btrfs_calc_metadata_size() we will need to reserve 4 times less space when using the free space tree and 2 times less space when not using it, putting less pressure on space reservation. So use helpers to reserve and release space for block group item updates that use btrfs_calc_metadata_size() for calculation of the space. Signed-off-by: Filipe Manana Signed-off-by: David Sterba --- fs/btrfs/delayed-ref.c | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) (limited to 'fs/btrfs/delayed-ref.c') diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c index 619d10eff0b4..de8434795913 100644 --- a/fs/btrfs/delayed-ref.c +++ b/fs/btrfs/delayed-ref.c @@ -125,6 +125,41 @@ void btrfs_update_delayed_refs_rsv(struct btrfs_trans_handle *trans) trans->delayed_ref_csum_deletions = 0; } +/* + * Adjust the size of the delayed refs block reserve for 1 block group item + * update. + */ +void btrfs_inc_delayed_refs_rsv_bg_updates(struct btrfs_fs_info *fs_info) +{ + struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_refs_rsv; + + spin_lock(&delayed_rsv->lock); + /* + * Updating a block group item does not result in new nodes/leaves and + * does not require changing the free space tree, only the extent tree + * or the block group tree, so this is all we need. + */ + delayed_rsv->size += btrfs_calc_metadata_size(fs_info, 1); + delayed_rsv->full = false; + spin_unlock(&delayed_rsv->lock); +} + +/* + * Adjust the size of the delayed refs block reserve to release space for 1 + * block group item update. + */ +void btrfs_dec_delayed_refs_rsv_bg_updates(struct btrfs_fs_info *fs_info) +{ + struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_refs_rsv; + const u64 num_bytes = btrfs_calc_metadata_size(fs_info, 1); + u64 released; + + released = btrfs_block_rsv_release(fs_info, delayed_rsv, num_bytes, NULL); + if (released > 0) + trace_btrfs_space_reservation(fs_info, "delayed_refs_rsv", + 0, released, 0); +} + /* * Transfer bytes to our delayed refs rsv. * -- cgit v1.2.3