On 15/04/2021 20:37, Josef Bacik wrote:
> On 4/15/21 9:58 AM, Johannes Thumshirn wrote:
>> When a file gets deleted on a zoned file system, the space freed is not
>> returned back into the block group's free space, but is migrated to
>> zone_unusable.
>>
>> As this zone_unusable space is behind the current write pointer it is not
>> possible to use it for new allocations. In the current implementation a
>> zone is reset once all of the block group's space is accounted as zone
>> unusable.
>>
>> This behaviour can lead to premature ENOSPC errors on a busy file system.
>>
>> Instead of only reclaiming the zone once it is completely unusable,
>> kick off a reclaim job once the amount of unusable bytes exceeds a user
>> configurable threshold between 51% and 100%. It can be set per mounted
>> filesystem via the sysfs tunable bg_reclaim_threshold which is set to 75%
>> per default.
>>
>> Similar to reclaiming unused block groups, these dirty block groups are
>> added to a to_reclaim list and then on a transaction commit, the reclaim
>> process is triggered but after we deleted unused block groups, which will
>> free space for the relocation process.
>>
>> Signed-off-by: Johannes Thumshirn <johannes.thumsh...@wdc.com>
>> ---
>> fs/btrfs/block-group.c | 96 ++++++++++++++++++++++++++++++++++++
>> fs/btrfs/block-group.h | 3 ++
>> fs/btrfs/ctree.h | 6 +++
>> fs/btrfs/disk-io.c | 13 +++++
>> fs/btrfs/free-space-cache.c | 9 +++-
>> fs/btrfs/sysfs.c | 35 +++++++++++++
>> fs/btrfs/volumes.c | 2 +-
>> fs/btrfs/volumes.h | 1 +
>> include/trace/events/btrfs.h | 12 +++++
>> 9 files changed, 175 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
>> index bbb5a6e170c7..3f06ea42c013 100644
>> --- a/fs/btrfs/block-group.c
>> +++ b/fs/btrfs/block-group.c
>> @@ -1485,6 +1485,92 @@ void btrfs_mark_bg_unused(struct btrfs_block_group
>> *bg)
>> spin_unlock(&fs_info->unused_bgs_lock);
>> }
>>
>> +void btrfs_reclaim_bgs_work(struct work_struct *work)
>> +{
>> + struct btrfs_fs_info *fs_info =
>> + container_of(work, struct btrfs_fs_info, reclaim_bgs_work);
>> + struct btrfs_block_group *bg;
>> + struct btrfs_space_info *space_info;
>> + int ret = 0;
>> +
>> + if (!test_bit(BTRFS_FS_OPEN, &fs_info->flags))
>> + return;
>> +
>> + if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_BALANCE))
>> + return;
>> +
>> + mutex_lock(&fs_info->reclaim_bgs_lock);
>> + spin_lock(&fs_info->unused_bgs_lock);
>> + while (!list_empty(&fs_info->reclaim_bgs)) {
>> + bg = list_first_entry(&fs_info->reclaim_bgs,
>> + struct btrfs_block_group,
>> + bg_list);
>> + list_del_init(&bg->bg_list);
>> +
>> + space_info = bg->space_info;
>> + spin_unlock(&fs_info->unused_bgs_lock);
>> +
>> + /* Don't want to race with allocators so take the groups_sem */
>> + down_write(&space_info->groups_sem);
>> +
>> + spin_lock(&bg->lock);
>> + if (bg->reserved || bg->pinned || bg->ro) {
>> + /*
>> + * We want to bail if we made new allocations or have
>> + * outstanding allocations in this block group. We do
>> + * the ro check in case balance is currently acting on
>> + * this block group.
>> + */
>> + spin_unlock(&bg->lock);
>> + up_write(&space_info->groups_sem);
>> + goto next;
>> + }
>> + spin_unlock(&bg->lock);
>> +
>
> Here I think we want a
>
> if (btrfs_fs_closing())
> goto next;
>
> so we don't block out a umount for all eternity. Thanks,
Right, will add.
