From 44d354abf33e92a5e73b965c84caf5a5d5e58a0b Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Mon, 13 Jul 2020 09:03:21 +0800 Subject: btrfs: relocation: review the call sites which can be interrupted by signal 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 Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/volumes.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) (limited to 'fs/btrfs/volumes.c') diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index c1a4dab8e811..537ccf66ee20 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -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); -- cgit v1.2.3