Re: [PATCH] mm/vmscan: DRY cleanup for do_try_to_free_pages()

[Jacob Wen <jian.w.wen@xxxxxxxxxx>]

On 12/18/20 6:51 PM, Michal Hocko wrote:
> On Fri 18-12-20 18:22:17, Jacob Wen wrote:
> > This patch reduces repetition of set_task_reclaim_state() around
> > do_try_to_free_pages().
> The changelog really should be talking about why this is needed/useful.
>  From the above it is not really clear whether you aimed at doing
> a clean up or this is a fix for some misbehavior. I do assume the former
> but this should be clearly articulated.

How about this?

mm/vmscan: remove duplicate code around do_try_to_free_pages()

This patch moves set_task_reclaim_state() into do_try_to_free_pages()
to avoid unnecessary repetition. It doesn't introduce functional
change.

> > Signed-off-by: Jacob Wen <jian.w.wen@xxxxxxxxxx>
> > ---
> >   mm/vmscan.c | 27 ++++++++++++++++-----------
> >   1 file changed, 16 insertions(+), 11 deletions(-)
> >
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 257cba79a96d..4bc244b23686 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -3023,6 +3023,10 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
> >   	pg_data_t *last_pgdat;
> >   	struct zoneref *z;
> >   	struct zone *zone;
> > +	unsigned long ret;
> > +
> > +	set_task_reclaim_state(current, &sc->reclaim_state);
> > +
> >   retry:
> >   	delayacct_freepages_start();
> >   
> > @@ -3069,12 +3073,16 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
> >   
> >   	delayacct_freepages_end();
> >   
> > -	if (sc->nr_reclaimed)
> > -		return sc->nr_reclaimed;
> > +	if (sc->nr_reclaimed) {
> > +		ret = sc->nr_reclaimed;
> > +		goto out;
> > +	}
> >   
> >   	/* Aborted reclaim to try compaction? don't OOM, then */
> > -	if (sc->compaction_ready)
> > -		return 1;
> > +	if (sc->compaction_ready) {
> > +		ret = 1;
> > +		goto out;
> > +	}
> >   
> >   	/*
> >   	 * We make inactive:active ratio decisions based on the node's
> > @@ -3101,7 +3109,10 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
> >   		goto retry;
> >   	}
> >   
> > -	return 0;
> > +	ret = 0;
> > +out:
> > +	set_task_reclaim_state(current, NULL);
> > +	return ret;
> >   }
> >   
> >   static bool allow_direct_reclaim(pg_data_t *pgdat)
> > @@ -3269,13 +3280,11 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
> >   	if (throttle_direct_reclaim(sc.gfp_mask, zonelist, nodemask))
> >   		return 1;
> >   
> > -	set_task_reclaim_state(current, &sc.reclaim_state);
> >   	trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask);
> >   
> >   	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
> >   
> >   	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
> > -	set_task_reclaim_state(current, NULL);
> >   
> >   	return nr_reclaimed;
> >   }
> > @@ -3347,7 +3356,6 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
> >   	 */
> >   	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
> >   
> > -	set_task_reclaim_state(current, &sc.reclaim_state);
> >   	trace_mm_vmscan_memcg_reclaim_begin(0, sc.gfp_mask);
> >   	noreclaim_flag = memalloc_noreclaim_save();
> >   
> > @@ -3355,7 +3363,6 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
> >   
> >   	memalloc_noreclaim_restore(noreclaim_flag);
> >   	trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
> > -	set_task_reclaim_state(current, NULL);
> >   
> >   	return nr_reclaimed;
> >   }
> > @@ -4023,11 +4030,9 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
> >   
> >   	fs_reclaim_acquire(sc.gfp_mask);
> >   	noreclaim_flag = memalloc_noreclaim_save();
> > -	set_task_reclaim_state(current, &sc.reclaim_state);
> >   
> >   	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
> >   
> > -	set_task_reclaim_state(current, NULL);
> >   	memalloc_noreclaim_restore(noreclaim_flag);
> >   	fs_reclaim_release(sc.gfp_mask);
> >   
> > --
> > 2.25.1