comment adding to mlocking in try_to_unmap_one

[KOSAKI Motohiro]

Current code doesn't tell us why we don't bother to nonlinear kindly.
This patch added small adding explanation.


Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
---
 mm/rmap.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 81a168c..c631407 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1061,7 +1061,11 @@ static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
 	if (list_empty(&mapping->i_mmap_nonlinear))
 		goto out;
 
-	/* We don't bother to try to find the munlocked page in nonlinears */
+	/*
+	 * We don't bother to try to find the munlocked page in nonlinears.
+	 * It's costly. Instead, later, page reclaim logic may call
+	 * try_to_unmap(TTU_MUNLOCK) and recover PG_mlocked lazily.
+	 */
 	if (MLOCK_PAGES && TTU_ACTION(flags) == TTU_MUNLOCK)
 		goto out;
 
-- 
1.6.2.5



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