diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 5fb4cb646c82..ab9d9ed20e0c 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -468,6 +468,7 @@ enum { BTRFS_BLOCK_RSV_TRANS, BTRFS_BLOCK_RSV_CHUNK, BTRFS_BLOCK_RSV_DELOPS, + BTRFS_BLOCK_RSV_DELREFS, BTRFS_BLOCK_RSV_EMPTY, BTRFS_BLOCK_RSV_TEMP, }; @@ -831,6 +832,8 @@ struct btrfs_fs_info { struct btrfs_block_rsv chunk_block_rsv; /* block reservation for delayed operations */ struct btrfs_block_rsv delayed_block_rsv; + /* block reservation for delayed refs */ + struct btrfs_block_rsv delayed_refs_rsv; struct btrfs_block_rsv empty_block_rsv; @@ -2816,6 +2819,13 @@ int btrfs_cond_migrate_bytes(struct btrfs_fs_info *fs_info, void btrfs_block_rsv_release(struct btrfs_fs_info *fs_info, struct btrfs_block_rsv *block_rsv, u64 num_bytes); +void btrfs_delayed_refs_rsv_release(struct btrfs_fs_info *fs_info, int nr); +void btrfs_update_delayed_refs_rsv(struct btrfs_trans_handle *trans); +int btrfs_delayed_refs_rsv_refill(struct btrfs_fs_info *fs_info, + enum btrfs_reserve_flush_enum flush); +void btrfs_migrate_to_delayed_refs_rsv(struct btrfs_fs_info *fs_info, + struct btrfs_block_rsv *src, + u64 num_bytes); int btrfs_inc_block_group_ro(struct btrfs_block_group_cache *cache); void btrfs_dec_block_group_ro(struct btrfs_block_group_cache *cache); void btrfs_put_block_group_cache(struct btrfs_fs_info *info); diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c index 48725fa757a3..cad36c99a483 100644 --- a/fs/btrfs/delayed-ref.c +++ b/fs/btrfs/delayed-ref.c @@ -473,12 +473,14 @@ inserted: * helper function to update the accounting in the head ref * existing and update must have the same bytenr */ -static noinline void -update_existing_head_ref(struct btrfs_delayed_ref_root *delayed_refs, +static noinline void update_existing_head_ref(struct btrfs_trans_handle *trans, struct btrfs_delayed_ref_head *existing, struct btrfs_delayed_ref_head *update, int *old_ref_mod_ret) { + struct btrfs_delayed_ref_root *delayed_refs = + &trans->transaction->delayed_refs; + struct btrfs_fs_info *fs_info = trans->fs_info; int old_ref_mod; BUG_ON(existing->is_data != update->is_data); @@ -536,10 +538,18 @@ update_existing_head_ref(struct btrfs_delayed_ref_root *delayed_refs, * versa we need to make sure to adjust pending_csums accordingly. */ if (existing->is_data) { - if (existing->total_ref_mod >= 0 && old_ref_mod < 0) + u64 csum_leaves = + btrfs_csum_bytes_to_leaves(fs_info, + existing->num_bytes); + + if (existing->total_ref_mod >= 0 && old_ref_mod < 0) { delayed_refs->pending_csums -= existing->num_bytes; - if (existing->total_ref_mod < 0 && old_ref_mod >= 0) + btrfs_delayed_refs_rsv_release(fs_info, csum_leaves); + } + if (existing->total_ref_mod < 0 && old_ref_mod >= 0) { delayed_refs->pending_csums += existing->num_bytes; + trans->delayed_ref_updates += csum_leaves; + } } spin_unlock(&existing->lock); } @@ -645,7 +655,7 @@ add_delayed_ref_head(struct btrfs_trans_handle *trans, && head_ref->qgroup_reserved && existing->qgroup_ref_root && existing->qgroup_reserved); - update_existing_head_ref(delayed_refs, existing, head_ref, + update_existing_head_ref(trans, existing, head_ref, old_ref_mod); /* * we've updated the existing ref, free the newly @@ -656,8 +666,12 @@ add_delayed_ref_head(struct btrfs_trans_handle *trans, } else { if (old_ref_mod) *old_ref_mod = 0; - if (head_ref->is_data && head_ref->ref_mod < 0) + if (head_ref->is_data && head_ref->ref_mod < 0) { delayed_refs->pending_csums += head_ref->num_bytes; + trans->delayed_ref_updates += + btrfs_csum_bytes_to_leaves(trans->fs_info, + head_ref->num_bytes); + } delayed_refs->num_heads++; delayed_refs->num_heads_ready++; atomic_inc(&delayed_refs->num_entries); @@ -793,6 +807,12 @@ int btrfs_add_delayed_tree_ref(struct btrfs_trans_handle *trans, ret = insert_delayed_ref(trans, delayed_refs, head_ref, &ref->node); spin_unlock(&delayed_refs->lock); + /* + * Need to update the delayed_refs_rsv with any changes we may have + * made. + */ + btrfs_update_delayed_refs_rsv(trans); + trace_add_delayed_tree_ref(fs_info, &ref->node, ref, action == BTRFS_ADD_DELAYED_EXTENT ? BTRFS_ADD_DELAYED_REF : action); @@ -874,6 +894,12 @@ int btrfs_add_delayed_data_ref(struct btrfs_trans_handle *trans, ret = insert_delayed_ref(trans, delayed_refs, head_ref, &ref->node); spin_unlock(&delayed_refs->lock); + /* + * Need to update the delayed_refs_rsv with any changes we may have + * made. + */ + btrfs_update_delayed_refs_rsv(trans); + trace_add_delayed_data_ref(trans->fs_info, &ref->node, ref, action == BTRFS_ADD_DELAYED_EXTENT ? BTRFS_ADD_DELAYED_REF : action); @@ -910,6 +936,12 @@ int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info, NULL, NULL, NULL); spin_unlock(&delayed_refs->lock); + + /* + * Need to update the delayed_refs_rsv with any changes we may have + * made. + */ + btrfs_update_delayed_refs_rsv(trans); return 0; } diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index cbb7cf4a993d..2f934a0b2148 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -2678,6 +2678,9 @@ int open_ctree(struct super_block *sb, btrfs_init_block_rsv(&fs_info->empty_block_rsv, BTRFS_BLOCK_RSV_EMPTY); btrfs_init_block_rsv(&fs_info->delayed_block_rsv, BTRFS_BLOCK_RSV_DELOPS); + btrfs_init_block_rsv(&fs_info->delayed_refs_rsv, + BTRFS_BLOCK_RSV_DELREFS); + atomic_set(&fs_info->async_delalloc_pages, 0); atomic_set(&fs_info->defrag_running, 0); atomic_set(&fs_info->qgroup_op_seq, 0); @@ -4446,6 +4449,7 @@ void btrfs_cleanup_dirty_bgs(struct btrfs_transaction *cur_trans, spin_unlock(&cur_trans->dirty_bgs_lock); btrfs_put_block_group(cache); + btrfs_delayed_refs_rsv_release(fs_info, 1); spin_lock(&cur_trans->dirty_bgs_lock); } spin_unlock(&cur_trans->dirty_bgs_lock); diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 32a68b6bbeea..54dc55b55a4b 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -2462,6 +2462,7 @@ static void cleanup_ref_head_accounting(struct btrfs_trans_handle *trans, struct btrfs_fs_info *fs_info = trans->fs_info; struct btrfs_delayed_ref_root *delayed_refs = &trans->transaction->delayed_refs; + int nr_items = 1; /* Dropping this ref head update. */ if (head->total_ref_mod < 0) { struct btrfs_space_info *space_info; @@ -2479,16 +2480,24 @@ static void cleanup_ref_head_accounting(struct btrfs_trans_handle *trans, -head->num_bytes, BTRFS_TOTAL_BYTES_PINNED_BATCH); + /* + * We had csum deletions accounted for in our delayed refs rsv, + * we need to drop the csum leaves for this update from our + * delayed_refs_rsv. + */ if (head->is_data) { spin_lock(&delayed_refs->lock); delayed_refs->pending_csums -= head->num_bytes; spin_unlock(&delayed_refs->lock); + nr_items += btrfs_csum_bytes_to_leaves(fs_info, + head->num_bytes); } } /* Also free its reserved qgroup space */ btrfs_qgroup_free_delayed_ref(fs_info, head->qgroup_ref_root, head->qgroup_reserved); + btrfs_delayed_refs_rsv_release(fs_info, nr_items); } static int cleanup_ref_head(struct btrfs_trans_handle *trans, @@ -3626,6 +3635,8 @@ again: */ mutex_lock(&trans->transaction->cache_write_mutex); while (!list_empty(&dirty)) { + bool drop_reserve = true; + cache = list_first_entry(&dirty, struct btrfs_block_group_cache, dirty_list); @@ -3698,6 +3709,7 @@ again: list_add_tail(&cache->dirty_list, &cur_trans->dirty_bgs); btrfs_get_block_group(cache); + drop_reserve = false; } spin_unlock(&cur_trans->dirty_bgs_lock); } else if (ret) { @@ -3708,6 +3720,8 @@ again: /* if its not on the io list, we need to put the block group */ if (should_put) btrfs_put_block_group(cache); + if (drop_reserve) + btrfs_delayed_refs_rsv_release(fs_info, 1); if (ret) break; @@ -3856,6 +3870,7 @@ int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans, /* if its not on the io list, we need to put the block group */ if (should_put) btrfs_put_block_group(cache); + btrfs_delayed_refs_rsv_release(fs_info, 1); spin_lock(&cur_trans->dirty_bgs_lock); } spin_unlock(&cur_trans->dirty_bgs_lock); @@ -5389,6 +5404,90 @@ int btrfs_cond_migrate_bytes(struct btrfs_fs_info *fs_info, return 0; } +/** + * btrfs_migrate_to_delayed_refs_rsv - transfer bytes to our delayed refs rsv. + * @fs_info - the fs info for our fs. + * @src - the source block rsv to transfer from. + * @num_bytes - the number of bytes to transfer. + * + * This transfers up to the num_bytes amount from the src rsv to the + * delayed_refs_rsv. Any extra bytes are returned to the space info. + */ +void btrfs_migrate_to_delayed_refs_rsv(struct btrfs_fs_info *fs_info, + struct btrfs_block_rsv *src, + u64 num_bytes) +{ + struct btrfs_block_rsv *delayed_refs_rsv = &fs_info->delayed_refs_rsv; + u64 to_free = 0; + + spin_lock(&src->lock); + src->reserved -= num_bytes; + src->size -= num_bytes; + spin_unlock(&src->lock); + + spin_lock(&delayed_refs_rsv->lock); + if (delayed_refs_rsv->size > delayed_refs_rsv->reserved) { + u64 delta = delayed_refs_rsv->size - + delayed_refs_rsv->reserved; + if (num_bytes > delta) { + to_free = num_bytes - delta; + num_bytes = delta; + } + } else { + to_free = num_bytes; + num_bytes = 0; + } + + if (num_bytes) + delayed_refs_rsv->reserved += num_bytes; + if (delayed_refs_rsv->reserved >= delayed_refs_rsv->size) + delayed_refs_rsv->full = 1; + spin_unlock(&delayed_refs_rsv->lock); + + if (num_bytes) + trace_btrfs_space_reservation(fs_info, "delayed_refs_rsv", + 0, num_bytes, 1); + if (to_free) + space_info_add_old_bytes(fs_info, delayed_refs_rsv->space_info, + to_free); +} + +/** + * btrfs_delayed_refs_rsv_refill - refill based on our delayed refs usage. + * @fs_info - the fs_info for our fs. + * @flush - control how we can flush for this reservation. + * + * This will refill the delayed block_rsv up to 1 items size worth of space and + * will return -ENOSPC if we can't make the reservation. + */ +int btrfs_delayed_refs_rsv_refill(struct btrfs_fs_info *fs_info, + enum btrfs_reserve_flush_enum flush) +{ + struct btrfs_block_rsv *block_rsv = &fs_info->delayed_refs_rsv; + u64 limit = btrfs_calc_trans_metadata_size(fs_info, 1); + u64 num_bytes = 0; + int ret = -ENOSPC; + + spin_lock(&block_rsv->lock); + if (block_rsv->reserved < block_rsv->size) { + num_bytes = block_rsv->size - block_rsv->reserved; + num_bytes = min(num_bytes, limit); + } + spin_unlock(&block_rsv->lock); + + if (!num_bytes) + return 0; + + ret = reserve_metadata_bytes(fs_info->extent_root, block_rsv, + num_bytes, flush); + if (ret) + return ret; + block_rsv_add_bytes(block_rsv, num_bytes, 0); + trace_btrfs_space_reservation(fs_info, "delayed_refs_rsv", + 0, num_bytes, 1); + return 0; +} + /* * This is for space we already have accounted in space_info->bytes_may_use, so * basically when we're returning space from block_rsv's. @@ -5709,6 +5808,31 @@ static int btrfs_inode_rsv_refill(struct btrfs_inode *inode, return ret; } +static u64 __btrfs_block_rsv_release(struct btrfs_fs_info *fs_info, + struct btrfs_block_rsv *block_rsv, + u64 num_bytes, u64 *qgroup_to_release) +{ + struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv; + struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_refs_rsv; + struct btrfs_block_rsv *target = delayed_rsv; + + if (target->full || target == block_rsv) + target = global_rsv; + + if (block_rsv->space_info != target->space_info) + target = NULL; + + return block_rsv_release_bytes(fs_info, block_rsv, target, num_bytes, + qgroup_to_release); +} + +void btrfs_block_rsv_release(struct btrfs_fs_info *fs_info, + struct btrfs_block_rsv *block_rsv, + u64 num_bytes) +{ + __btrfs_block_rsv_release(fs_info, block_rsv, num_bytes, NULL); +} + /** * btrfs_inode_rsv_release - release any excessive reservation. * @inode - the inode we need to release from. @@ -5723,7 +5847,6 @@ static int btrfs_inode_rsv_refill(struct btrfs_inode *inode, static void btrfs_inode_rsv_release(struct btrfs_inode *inode, bool qgroup_free) { struct btrfs_fs_info *fs_info = inode->root->fs_info; - struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv; struct btrfs_block_rsv *block_rsv = &inode->block_rsv; u64 released = 0; u64 qgroup_to_release = 0; @@ -5733,8 +5856,8 @@ static void btrfs_inode_rsv_release(struct btrfs_inode *inode, bool qgroup_free) * are releasing 0 bytes, and then we'll just get the reservation over * the size free'd. */ - released = block_rsv_release_bytes(fs_info, block_rsv, global_rsv, 0, - &qgroup_to_release); + released = __btrfs_block_rsv_release(fs_info, block_rsv, 0, + &qgroup_to_release); if (released > 0) trace_btrfs_space_reservation(fs_info, "delalloc", btrfs_ino(inode), released, 0); @@ -5745,16 +5868,26 @@ static void btrfs_inode_rsv_release(struct btrfs_inode *inode, bool qgroup_free) qgroup_to_release); } -void btrfs_block_rsv_release(struct btrfs_fs_info *fs_info, - struct btrfs_block_rsv *block_rsv, - u64 num_bytes) +/** + * btrfs_delayed_refs_rsv_release - release a ref head's reservation. + * @fs_info - the fs_info for our fs. + * @nr - the number of items to drop. + * + * This drops the delayed ref head's count from the delayed refs rsv and frees + * any excess reservation we had. + */ +void btrfs_delayed_refs_rsv_release(struct btrfs_fs_info *fs_info, int nr) { + struct btrfs_block_rsv *block_rsv = &fs_info->delayed_refs_rsv; struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv; + u64 num_bytes = btrfs_calc_trans_metadata_size(fs_info, nr); + u64 released = 0; - if (global_rsv == block_rsv || - block_rsv->space_info != global_rsv->space_info) - global_rsv = NULL; - block_rsv_release_bytes(fs_info, block_rsv, global_rsv, num_bytes, NULL); + released = block_rsv_release_bytes(fs_info, block_rsv, global_rsv, + num_bytes, NULL); + if (released) + trace_btrfs_space_reservation(fs_info, "delayed_refs_rsv", + 0, released, 0); } static void update_global_block_rsv(struct btrfs_fs_info *fs_info) @@ -5819,9 +5952,10 @@ static void init_global_block_rsv(struct btrfs_fs_info *fs_info) fs_info->trans_block_rsv.space_info = space_info; fs_info->empty_block_rsv.space_info = space_info; fs_info->delayed_block_rsv.space_info = space_info; + fs_info->delayed_refs_rsv.space_info = space_info; - fs_info->extent_root->block_rsv = &fs_info->global_block_rsv; - fs_info->csum_root->block_rsv = &fs_info->global_block_rsv; + fs_info->extent_root->block_rsv = &fs_info->delayed_refs_rsv; + fs_info->csum_root->block_rsv = &fs_info->delayed_refs_rsv; fs_info->dev_root->block_rsv = &fs_info->global_block_rsv; fs_info->tree_root->block_rsv = &fs_info->global_block_rsv; if (fs_info->quota_root) @@ -5841,8 +5975,34 @@ static void release_global_block_rsv(struct btrfs_fs_info *fs_info) WARN_ON(fs_info->chunk_block_rsv.reserved > 0); WARN_ON(fs_info->delayed_block_rsv.size > 0); WARN_ON(fs_info->delayed_block_rsv.reserved > 0); + WARN_ON(fs_info->delayed_refs_rsv.reserved > 0); + WARN_ON(fs_info->delayed_refs_rsv.size > 0); } +/* + * btrfs_update_delayed_refs_rsv - adjust the size of the delayed refs rsv + * @trans - the trans that may have generated delayed refs + * + * This is to be called anytime we may have adjusted trans->delayed_ref_updates, + * it'll calculate the additional size and add it to the delayed_refs_rsv. + */ +void btrfs_update_delayed_refs_rsv(struct btrfs_trans_handle *trans) +{ + struct btrfs_fs_info *fs_info = trans->fs_info; + struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_refs_rsv; + u64 num_bytes; + + if (!trans->delayed_ref_updates) + return; + + num_bytes = btrfs_calc_trans_metadata_size(fs_info, + trans->delayed_ref_updates); + spin_lock(&delayed_rsv->lock); + delayed_rsv->size += num_bytes; + delayed_rsv->full = 0; + spin_unlock(&delayed_rsv->lock); + trans->delayed_ref_updates = 0; +} /* * To be called after all the new block groups attached to the transaction @@ -6135,6 +6295,7 @@ static int update_block_group(struct btrfs_trans_handle *trans, u64 old_val; u64 byte_in_group; int factor; + int ret = 0; /* block accounting for super block */ spin_lock(&info->delalloc_root_lock); @@ -6148,8 +6309,10 @@ static int update_block_group(struct btrfs_trans_handle *trans, while (total) { cache = btrfs_lookup_block_group(info, bytenr); - if (!cache) - return -ENOENT; + if (!cache) { + ret = -ENOENT; + break; + } factor = btrfs_bg_type_to_factor(cache->flags); /* @@ -6208,6 +6371,7 @@ static int update_block_group(struct btrfs_trans_handle *trans, list_add_tail(&cache->dirty_list, &trans->transaction->dirty_bgs); trans->transaction->num_dirty_bgs++; + trans->delayed_ref_updates++; btrfs_get_block_group(cache); } spin_unlock(&trans->transaction->dirty_bgs_lock); @@ -6225,7 +6389,10 @@ static int update_block_group(struct btrfs_trans_handle *trans, total -= num_bytes; bytenr += num_bytes; } - return 0; + + /* Modified block groups are accounted for in the delayed_refs_rsv. */ + btrfs_update_delayed_refs_rsv(trans); + return ret; } static u64 first_logical_byte(struct btrfs_fs_info *fs_info, u64 search_start) @@ -8371,7 +8538,12 @@ again: goto again; } - if (btrfs_test_opt(fs_info, ENOSPC_DEBUG)) { + /* + * The global reserve still exists to save us from ourselves, so don't + * warn_on if we are short on our delayed refs reserve. + */ + if (block_rsv->type != BTRFS_BLOCK_RSV_DELREFS && + btrfs_test_opt(fs_info, ENOSPC_DEBUG)) { static DEFINE_RATELIMIT_STATE(_rs, DEFAULT_RATELIMIT_INTERVAL * 10, /*DEFAULT_RATELIMIT_BURST*/ 1); @@ -10304,6 +10476,7 @@ void btrfs_create_pending_block_groups(struct btrfs_trans_handle *trans) add_block_group_free_space(trans, block_group); /* already aborted the transaction if it failed. */ next: + btrfs_delayed_refs_rsv_release(fs_info, 1); list_del_init(&block_group->bg_list); } btrfs_trans_release_chunk_metadata(trans); @@ -10381,6 +10554,8 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans, u64 bytes_used, link_block_group(cache); list_add_tail(&cache->bg_list, &trans->new_bgs); + trans->delayed_ref_updates++; + btrfs_update_delayed_refs_rsv(trans); set_avail_alloc_bits(fs_info, type); return 0; @@ -10418,6 +10593,7 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans, int factor; struct btrfs_caching_control *caching_ctl = NULL; bool remove_em; + bool remove_rsv = false; block_group = btrfs_lookup_block_group(fs_info, group_start); BUG_ON(!block_group); @@ -10482,6 +10658,7 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans, if (!list_empty(&block_group->dirty_list)) { list_del_init(&block_group->dirty_list); + remove_rsv = true; btrfs_put_block_group(block_group); } spin_unlock(&trans->transaction->dirty_bgs_lock); @@ -10691,6 +10868,8 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans, ret = btrfs_del_item(trans, root, path); out: + if (remove_rsv) + btrfs_delayed_refs_rsv_release(fs_info, 1); btrfs_free_path(path); return ret; } diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index 67e84939b758..e18eb75e6fa3 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -454,7 +454,7 @@ start_transaction(struct btrfs_root *root, unsigned int num_items, bool enforce_qgroups) { struct btrfs_fs_info *fs_info = root->fs_info; - + struct btrfs_block_rsv *delayed_refs_rsv = &fs_info->delayed_refs_rsv; struct btrfs_trans_handle *h; struct btrfs_transaction *cur_trans; u64 num_bytes = 0; @@ -483,13 +483,28 @@ start_transaction(struct btrfs_root *root, unsigned int num_items, * the appropriate flushing if need be. */ if (num_items && root != fs_info->chunk_root) { + struct btrfs_block_rsv *rsv = &fs_info->trans_block_rsv; + u64 delayed_refs_bytes = 0; + qgroup_reserved = num_items * fs_info->nodesize; ret = btrfs_qgroup_reserve_meta_pertrans(root, qgroup_reserved, enforce_qgroups); if (ret) return ERR_PTR(ret); + /* + * We want to reserve all the bytes we may need all at once, so + * we only do 1 enospc flushing cycle per transaction start. We + * accomplish this by simply assuming we'll do 2 x num_items + * worth of delayed refs updates in this trans handle, and + * refill that amount for whatever is missing in the reserve. + */ num_bytes = btrfs_calc_trans_metadata_size(fs_info, num_items); + if (delayed_refs_rsv->full == 0) { + delayed_refs_bytes = num_bytes; + num_bytes <<= 1; + } + /* * Do the reservation for the relocation root creation */ @@ -498,8 +513,24 @@ start_transaction(struct btrfs_root *root, unsigned int num_items, reloc_reserved = true; } - ret = btrfs_block_rsv_add(root, &fs_info->trans_block_rsv, - num_bytes, flush); + ret = btrfs_block_rsv_add(root, rsv, num_bytes, flush); + if (ret) + goto reserve_fail; + if (delayed_refs_bytes) { + btrfs_migrate_to_delayed_refs_rsv(fs_info, rsv, + delayed_refs_bytes); + num_bytes -= delayed_refs_bytes; + } + } else if (num_items == 0 && flush == BTRFS_RESERVE_FLUSH_ALL && + !delayed_refs_rsv->full) { + /* + * Some people call with btrfs_start_transaction(root, 0) + * because they can be throttled, but have some other mechanism + * for reserving space. We still want these guys to refill the + * delayed block_rsv so just add 1 items worth of reservation + * here. + */ + ret = btrfs_delayed_refs_rsv_refill(fs_info, flush); if (ret) goto reserve_fail; }