btrfs: relocation: review the call sites which can be interrupted by signal (44d354ab) · Commits · 戴 / test

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 least amount 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. CC: stable@vger.kernel.org # 5.4+ Signed-off-by:

Qu Wenruo <wqu@suse.com> Reviewed-by:

David Sterba <dsterba@suse.com> Signed-off-by:

David Sterba <dsterba@suse.com>

fs/btrfs/relocation.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -1686,12 +1686,20 @@ 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 size 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;

fs/btrfs/volumes.c

+16 −1

Original line number	Diff line number	Diff line
		@@ -4135,7 +4135,22 @@ 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);

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