quoted

quoted

<snip>

quoted

 			      struct scan_control *sc)
 {
+	enum bdi_queue_status ret = QUEUEWRITE_DENIED;
+
 	if (current->flags & PF_SWAPWRITE)
-		return 1;
+		return QUEUEWRITE_ALLOWED;
 	if (!bdi_write_congested(bdi))
-		return 1;
+		return QUEUEWRITE_ALLOWED;
+	else
+		ret = QUEUEWRITE_CONGESTED;
 	if (bdi == current->backing_dev_info)
-		return 1;
+		return QUEUEWRITE_ALLOWED;
 
 	/* lumpy reclaim for hugepage often need a lot of write */
 	if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
-		return 1;
-	return 0;
+		return QUEUEWRITE_ALLOWED;
+	return ret;
 }

The function can't return QUEUEXXX_DENIED.
It can affect disable_lumpy_reclaim. 

Yes, but that change was made in "vmscan: Narrow the scenarios lumpy
reclaim uses synchrounous reclaim". Maybe I am misunderstanding your
objection.

I means current may_write_to_queue never returns QUEUEWRITE_DENIED.
What's the role of it?

As of now, little point because QUEUEWRITE_CONGESTED implies denied. I was allowing
the possibility of distinguishing between these cases in the future depending
on what happened with wait_iff_congested(). I will drop it for simplicity
and reintroduce it when or if there is a distinction between
denied and congested.

In addition, we don't need disable_lumpy_reclaim_mode() in pageout.
That's because both PAGE_KEEP and PAGE_KEEP_CONGESTED go to keep_locked
and calls disable_lumpy_reclaim_mode at last. 

True, good spot.

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

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