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Wong" To: Dave Chinner Cc: linux-xfs@vger.kernel.org, chris@onthe.net.au Subject: Re: [PATCH 2/2] xfs: introduce xfs_inodegc_push() Message-ID: References: <20220524063802.1938505-1-david@fromorbit.com> <20220524063802.1938505-3-david@fromorbit.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220524063802.1938505-3-david@fromorbit.com> Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Tue, May 24, 2022 at 04:38:02PM +1000, Dave Chinner wrote: > From: Dave Chinner > > 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 > Signed-off-by: Dave Chinner > --- > 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 >