@@ -1686,12 +1686,21 @@ static noinline_for_stack int merge_reloc_root(struct reloc_control *rc,
btrfs_unlock_up_safe(path, 0);
}
- min_reserved = fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
+ /*
+ * In merge_reloc_root(), we modify the upper level pointer to swap
+ * the tree blocks between reloc tree and subvolume tree.
+ * Thus for tree block COW, we COW at most from level 1 to root level
+ * for each tree.
+ *
+ * Thus the needed metadata space is at most root_level * nodesize,
+ * and * 2 since we have two trees to COW.
+ */
+ min_reserved = fs_info->nodesize * btrfs_root_level(root_item) * 2;
memset(&next_key, 0, sizeof(next_key));
while (1) {
ret = btrfs_block_rsv_refill(root, rc->block_rsv, min_reserved,
- BTRFS_RESERVE_FLUSH_ALL);
+ BTRFS_RESERVE_FLUSH_LIMIT);
if (ret) {
err = ret;
goto out;
@@ -4135,7 +4135,19 @@ int btrfs_balance(struct btrfs_fs_info *fs_info,
mutex_lock(&fs_info->balance_mutex);
if (ret == -ECANCELED && atomic_read(&fs_info->balance_pause_req))
btrfs_info(fs_info, "balance: paused");
- else if (ret == -ECANCELED && atomic_read(&fs_info->balance_cancel_req))
+ /*
+ * Balance can be canceled by:
+ * - Regular cancel request
+ * Then ret == -ECANCELED and balance_cancel_req > 0
+ * - Fatal signal to "btrfs" process
+ * Either the signal caught by wait_reserve_ticket() and callers
+ * got -EINTR, or caught by btrfs_should_cancel_balance() and
+ * got -ECANCELED.
+ * Either way, in this case balance_cancel_req = 0, and
+ * ret == -EINTR or ret == -ECANCELED.
+ * So here we only check the return value to catch canceled balance.
+ */
+ else if (ret == -ECANCELED || ret == -EINTR)
btrfs_info(fs_info, "balance: canceled");
else
btrfs_info(fs_info, "balance: ended with status: %d", ret);
Since most metadata reservation calls can return -EINTR when get interrupted by fatal signal, we need to review the all the metadata reservation call sites. In relocation code, the metadata reservation happens in the following sites: - btrfs_block_rsv_refill() in merge_reloc_root() merge_reloc_root() is a pretty critical section, we don't want to be interrupted by signal, so change the flush status to BTRFS_RESERVE_FLUSH_LIMIT, so it won't get interrupted by signal. Since such change can be ENPSPC-prone, also shrink the amount of metadata to reserve a little to avoid deadly ENOSPC there. - btrfs_block_rsv_refill() in reserve_metadata_space() It calls with BTRFS_RESERVE_FLUSH_LIMIT, which won't get interrupted by signal. - btrfs_block_rsv_refill() in prepare_to_relocate() - btrfs_block_rsv_add() in prepare_to_relocate() - btrfs_block_rsv_refill() in relocate_block_group() - btrfs_delalloc_reserve_metadata() in relocate_file_extent_cluster() - btrfs_start_transaction() in relocate_block_group() - btrfs_start_transaction() in create_reloc_inode() Can be interrupted by fatal signal and we can handle it easily. For these call sites, just catch the -EINTR value in btrfs_balance() and count them as canceled. Signed-off-by: Qu Wenruo <wqu@suse.com> --- fs/btrfs/relocation.c | 13 +++++++++++-- fs/btrfs/volumes.c | 14 +++++++++++++- 2 files changed, 24 insertions(+), 3 deletions(-)