On Tue, May 24, 2022 at 1:37 PM Dave Chinner <david@xxxxxxxxxxxxx> wrote:
>
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> The current blocking mechanism for pushing the inodegc queue out to
> disk can result in systems becoming unusable when there is a long
> running inodegc operation. This is because the statfs()
> implementation currently issues a blocking flush of the inodegc
> queue and a significant number of common system utilities will call
> statfs() to discover something about the underlying filesystem.
>
> This can result in userspace operations getting stuck on inodegc
> progress, and when trying to remove a heavily reflinked file on slow
> storage with a full journal, this can result in delays measuring in
> hours.
>
> Avoid this problem by adding "push" function that expedites the
> flushing of the inodegc queue, but doesn't wait for it to complete.
>
> Convert xfs_fs_statfs() to use this mechanism so it doesn't block
> but it does ensure that queued operations are expedited.
>
> Fixes: ab23a7768739 ("xfs: per-cpu deferred inode inactivation queues")
> Reported-by: Chris Dunlop <chris@xxxxxxxxxxxx>
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---
> fs/xfs/xfs_icache.c | 20 +++++++++++++++-----
> fs/xfs/xfs_icache.h | 1 +
> fs/xfs/xfs_super.c | 7 +++++--
> fs/xfs/xfs_trace.h | 1 +
> 4 files changed, 22 insertions(+), 7 deletions(-)
>
> diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> index 786702273621..2609825d53ee 100644
> --- a/fs/xfs/xfs_icache.c
> +++ b/fs/xfs/xfs_icache.c
> @@ -1862,19 +1862,29 @@ xfs_inodegc_worker(
> }
>
> /*
> - * Force all currently queued inode inactivation work to run immediately and
> - * wait for the work to finish.
> + * Expedite all pending inodegc work to run immediately. This does not wait for
> + * completion of the work.
> */
> void
> -xfs_inodegc_flush(
> +xfs_inodegc_push(
> struct xfs_mount *mp)
> {
> if (!xfs_is_inodegc_enabled(mp))
> return;
> + trace_xfs_inodegc_push(mp, __return_address);
> + xfs_inodegc_queue_all(mp);
> +}
>
> +/*
> + * Force all currently queued inode inactivation work to run immediately and
> + * wait for the work to finish.
> + */
> +void
> +xfs_inodegc_flush(
> + struct xfs_mount *mp)
> +{
> + xfs_inodegc_push(mp);
> trace_xfs_inodegc_flush(mp, __return_address);
Unintentional(?) change of behavior:
trace_xfs_inodegc_flush() will be called in
(!xfs_is_inodegc_enabled(mp)) case.
I also wonder if trace_xfs_inodegc_flush()
should not be before trace_xfs_inodegc_push() in this flow,
but this is just a matter of tracing conventions and you should
know best how it will be convenient for xfs developers to be
reading the trace events stream.
Thanks,
Amir.
