On 16.08.19 г. 17:19 ч., Josef Bacik wrote:
> Now that we no longer partially fill tickets we need to rework
> wake_all_tickets to call btrfs_try_to_wakeup_tickets() in order to see
> if any subsequent tickets are able to be satisfied. If our tickets_id
> changes we know something happened and we can keep flushing.
>
> Also if we find a ticket that is smaller than the first ticket in our
> queue then we want to retry the flushing loop again in case
> may_commit_transaction() decides we could satisfy the ticket by
> committing the transaction.
>
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
> ---
> fs/btrfs/space-info.c | 34 +++++++++++++++++++++++++++-------
> 1 file changed, 27 insertions(+), 7 deletions(-)
>
> diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
> index 8a1c7ada67cb..bd485be783b8 100644
> --- a/fs/btrfs/space-info.c
> +++ b/fs/btrfs/space-info.c
> @@ -676,19 +676,39 @@ static inline int need_do_async_reclaim(struct btrfs_fs_info *fs_info,
> !test_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state));
> }
>
> -static bool wake_all_tickets(struct list_head *head)
> +static bool wake_all_tickets(struct btrfs_fs_info *fs_info,
> + struct btrfs_space_info *space_info)
> {
> struct reserve_ticket *ticket;
> + u64 tickets_id = space_info->tickets_id;
> + u64 first_ticket_bytes = 0;
> +
> + while (!list_empty(&space_info->tickets) &&
> + tickets_id == space_info->tickets_id) {
> + ticket = list_first_entry(&space_info->tickets,
> + struct reserve_ticket, list);
> +
> + /*
> + * may_commit_transaction will avoid committing the transaction
> + * if it doesn't feel like the space reclaimed by the commit
> + * would result in the ticket succeeding. However if we have a
> + * smaller ticket in the queue it may be small enough to be
> + * satisified by committing the transaction, so if any
> + * subsequent ticket is smaller than the first ticket go ahead
> + * and send us back for another loop through the enospc flushing
> + * code.
> + */
> + if (first_ticket_bytes == 0)
> + first_ticket_bytes = ticket->bytes;
> + else if (first_ticket_bytes > ticket->bytes)
> + return true;
>
> - while (!list_empty(head)) {
> - ticket = list_first_entry(head, struct reserve_ticket, list);
> list_del_init(&ticket->list);
> ticket->error = -ENOSPC;
> wake_up(&ticket->wait);
> - if (ticket->bytes != ticket->orig_bytes)
> - return true;
> + btrfs_try_to_wakeup_tickets(fs_info, space_info);
So the change in this logic is directly related to the implementation of
btrfs_try_to_wakeup_tickets. Because when we fail and remove a ticket in
this function we give a chance that the next ticket *could* be
satisfied. But how well does that work in practice, given you fail
normal prio tickets here, whereas btrfs_try_to_wakeup_tickets first
checks the prio ticket. So even if you are failing normal ticket but
there is one unsatifiable prio ticket that won't really change anything.
> }
> - return false;
> + return (tickets_id != space_info->tickets_id);
> }
>
> /*
> @@ -756,7 +776,7 @@ static void btrfs_async_reclaim_metadata_space(struct work_struct *work)
> if (flush_state > COMMIT_TRANS) {
> commit_cycles++;
> if (commit_cycles > 2) {
> - if (wake_all_tickets(&space_info->tickets)) {
> + if (wake_all_tickets(fs_info, space_info)) {
> flush_state = FLUSH_DELAYED_ITEMS_NR;
> commit_cycles--;
> } else {
>
