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@xxxxxxxxxx>
---
I remembered this old patch when we were discussing the more important
ecf5fc6e9654 "mm, vmscan: Do not wait for page writeback for GFP_NOFS
allocations", and now retested it against mmotm.
mm/vmscan.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
--- mmotm/mm/vmscan.c 2015-08-17 18:46:26.601521575 -0700
+++ linux/mm/vmscan.c 2015-08-17 18:53:41.335108240 -0700
@@ -991,7 +991,7 @@ static unsigned long shrink_page_list(st
* __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
@@ -1021,12 +1021,15 @@ static unsigned long shrink_page_list(st
*/
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;
}
}
--
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