linux-kernel - [PATCH v2] MM: handle THP in swap_*page_fs()

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Date:   Mon, 02 May 2022 15:31:29 +1000
From:   "NeilBrown" <neilb@...e.de>
To:     "Andrew Morton" <akpm@...ux-foundation.org>,
        "Miaohe Lin" <linmiaohe@...wei.com>
Cc:     "Geert Uytterhoeven" <geert+renesas@...der.be>,
        "Christoph Hellwig" <hch@....de>, linux-nfs@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Matthew Wilcox <willy@...radead.org>
Subject: [PATCH v2] MM: handle THP in swap_*page_fs() - count_vm_events()


We need to use count_swpout_vm_event() for sio_write_complete() to get
correct counting.

Note that THP swap in (if it ever happens) is current accounted 1 for
each page, whether HUGE or normal.  This is different from swap-out
accounting.

This patch should be squashed into
    MM: handle THP in swap_*page_fs()

Reported-by: Miaohe Lin <linmiaohe@...wei.com>
Signed-off-by: NeilBrown <neilb@...e.de>
---
 mm/page_io.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/page_io.c b/mm/page_io.c
index d636a3531cad..1b8075ef3418 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -280,8 +280,10 @@ static void sio_write_complete(struct kiocb *iocb, long ret)
 			set_page_dirty(page);
 			ClearPageReclaim(page);
 		}
-	} else
-		count_vm_events(PSWPOUT, sio->pages);
+	} else {
+		for (p = 0; p < sio->pages; p++)
+			count_swpout_vm_event(sio->bvec[p].bv_page);
+	}
 
 	for (p = 0; p < sio->pages; p++)
 		end_page_writeback(sio->bvec[p].bv_page);
-- 
2.36.0