On Mon, Mar 16, 2020 at 03:42:31PM +0100, Christoph Hellwig wrote:
> Merge xlog_state_set_callback into its only caller, which makes the iclog
> I/O completion handling a little easier to follow.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
> fs/xfs/xfs_log.c | 74 +++++++++++++++++++++---------------------------
> 1 file changed, 33 insertions(+), 41 deletions(-)
>
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index 899c324d07e2..865dd1e08679 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -2645,46 +2645,6 @@ xlog_get_lowest_lsn(
> return lowest_lsn;
> }
>
> -/*
> - * Completion of a iclog IO does not imply that a transaction has completed, as
> - * transactions can be large enough to span many iclogs. We cannot change the
> - * tail of the log half way through a transaction as this may be the only
> - * transaction in the log and moving the tail to point to the middle of it
> - * will prevent recovery from finding the start of the transaction. Hence we
> - * should only update the last_sync_lsn if this iclog contains transaction
> - * completion callbacks on it.
> - *
> - * We have to do this before we drop the icloglock to ensure we are the only one
> - * that can update it.
> - *
> - * If we are moving the last_sync_lsn forwards, we also need to ensure we kick
> - * the reservation grant head pushing. This is due to the fact that the push
> - * target is bound by the current last_sync_lsn value. Hence if we have a large
> - * amount of log space bound up in this committing transaction then the
> - * last_sync_lsn value may be the limiting factor preventing tail pushing from
> - * freeing space in the log. Hence once we've updated the last_sync_lsn we
> - * should push the AIL to ensure the push target (and hence the grant head) is
> - * no longer bound by the old log head location and can move forwards and make
> - * progress again.
> - */
> -static void
> -xlog_state_set_callback(
> - struct xlog *log,
> - struct xlog_in_core *iclog,
> - xfs_lsn_t header_lsn)
> -{
> - iclog->ic_state = XLOG_STATE_CALLBACK;
> -
> - ASSERT(XFS_LSN_CMP(atomic64_read(&log->l_last_sync_lsn),
> - header_lsn) <= 0);
> -
> - if (list_empty_careful(&iclog->ic_callbacks))
> - return;
> -
> - atomic64_set(&log->l_last_sync_lsn, header_lsn);
> - xlog_grant_push_ail(log, 0);
> -}
> -
> /*
> * Keep processing entries in the iclog callback list until we come around and
> * it is empty. We need to atomically see that the list is empty and change the
> @@ -2741,7 +2701,39 @@ xlog_state_iodone_process_iclog(
> if (lowest_lsn && XFS_LSN_CMP(lowest_lsn, header_lsn) < 0)
> return false;
>
> - xlog_state_set_callback(log, iclog, header_lsn);
> + iclog->ic_state = XLOG_STATE_CALLBACK;
> +
> + ASSERT(XFS_LSN_CMP(atomic64_read(&log->l_last_sync_lsn),
> + header_lsn) <= 0);
> +
> + /*
> + * Completion of an iclog I/O does not imply that a transaction has
> + * completed, as transactions can be large enough to span multiple
> + * iclogs. We cannot change the tail of the log half way through a
> + * transaction as this may be the only transaction in the log and moving
> + * the tail to point to the middle of it will prevent recovery from
> + * finding the start of the transaction. Hence we should only update
> + * the last_sync_lsn if this iclog contains transaction completion
> + * callbacks on it.
> + *
> + * We have to do this before we drop the icloglock to ensure we are the
> + * only one that can update it.
> + *
> + * If we are moving last_sync_lsn forwards, we also need to ensure we
> + * kick the reservation grant head pushing. This is due to the fact that
> + * the push target is bound by the current last_sync_lsn value. If we
> + * have a large amount of log space bound up in this committing
> + * transaction then the last_sync_lsn value may be the limiting factor
> + * preventing tail pushing from freeing space in the log. Hence once
> + * we've updated the last_sync_lsn we should push the AIL to ensure the
> + * push target (and hence the grant head) is no longer bound by the old
> + * log head location and can move forwards and make progress again.
> + */
> + if (!list_empty_careful(&iclog->ic_callbacks)) {
> + atomic64_set(&log->l_last_sync_lsn, header_lsn);
> + xlog_grant_push_ail(log, 0);
> + }
> +
> xlog_state_do_iclog_callbacks(log, iclog);
>
> iclog->ic_state = XLOG_STATE_DIRTY;
> --
> 2.24.1
>
