mm, vmscan: unlock page while waiting on writeback
This is merely a politeness: I've not found that shrink_page_list()
leads to deadlock with the page it holds locked across
wait_on_page_writeback(); but nevertheless, why hold others off by
keeping the page locked there?
And while we're at it: remove the mistaken "not " from the commentary on
this Case 3 (and a distracting blank line from Case 2, if I may).
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 8276a3a..2d978b2 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -985,7 +985,7 @@
* __GFP_IO|__GFP_FS for this reason); but more thought
* would probably show more reasons.
*
- * 3) Legacy memcg encounters a page that is not already marked
+ * 3) Legacy memcg encounters a page that is already marked
* PageReclaim. memcg does not have any dirty pages
* throttling so we could easily OOM just because too many
* pages are in writeback and there is nothing else to
@@ -1015,12 +1015,15 @@
*/
SetPageReclaim(page);
nr_writeback++;
-
goto keep_locked;
/* Case 3 above */
} else {
+ unlock_page(page);
wait_on_page_writeback(page);
+ /* then go back and try same page again */
+ list_add_tail(&page->lru, page_list);
+ continue;
}
}