On Tue, May 24, 2022 at 04:38:02PM +1000, Dave Chinner 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);
> -
> - xfs_inodegc_queue_all(mp);
> flush_workqueue(mp->m_inodegc_wq);
> }
>
> diff --git a/fs/xfs/xfs_icache.h b/fs/xfs/xfs_icache.h
> index 2e4cfddf8b8e..6cd180721659 100644
> --- a/fs/xfs/xfs_icache.h
> +++ b/fs/xfs/xfs_icache.h
> @@ -76,6 +76,7 @@ void xfs_blockgc_stop(struct xfs_mount *mp);
> void xfs_blockgc_start(struct xfs_mount *mp);
>
> void xfs_inodegc_worker(struct work_struct *work);
> +void xfs_inodegc_push(struct xfs_mount *mp);
> void xfs_inodegc_flush(struct xfs_mount *mp);
> void xfs_inodegc_stop(struct xfs_mount *mp);
> void xfs_inodegc_start(struct xfs_mount *mp);
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index 62f6b97355a2..e14101813851 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -796,8 +796,11 @@ xfs_fs_statfs(
> xfs_extlen_t lsize;
> int64_t ffree;
>
> - /* Wait for whatever inactivations are in progress. */
> - xfs_inodegc_flush(mp);
> + /*
> + * Expedite background inodegc but don't wait. We do not want to block
> + * here waiting hours for a billion extent file to be truncated.
> + */
> + xfs_inodegc_push(mp);
I think the same "don't wait forever for inodegc during a stats call"
logic applies to the _inodegc_flush calls in xfs_qm_scall_getquota*,
wouldn't it?
The logic in this patch looks solid otherwise.
--D
>
> statp->f_type = XFS_SUPER_MAGIC;
> statp->f_namelen = MAXNAMELEN - 1;
> diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> index d32026585c1b..0fa1b7a2918c 100644
> --- a/fs/xfs/xfs_trace.h
> +++ b/fs/xfs/xfs_trace.h
> @@ -240,6 +240,7 @@ DEFINE_EVENT(xfs_fs_class, name, \
> TP_PROTO(struct xfs_mount *mp, void *caller_ip), \
> TP_ARGS(mp, caller_ip))
> DEFINE_FS_EVENT(xfs_inodegc_flush);
> +DEFINE_FS_EVENT(xfs_inodegc_push);
> DEFINE_FS_EVENT(xfs_inodegc_start);
> DEFINE_FS_EVENT(xfs_inodegc_stop);
> DEFINE_FS_EVENT(xfs_inodegc_queue);
> --
> 2.35.1
>
