linux-kernel - [PATCH 04/12] mm, thp, tmpfs: split huge page when moving from page cache to swap

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Message-ID: <20131015001228.GE3432@hippobay.mtv.corp.google.com>
Date:	Mon, 14 Oct 2013 17:12:28 -0700
From:	Ning Qu <quning@...gle.com>
To:	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Hugh Dickins <hughd@...gle.com>
Cc:	Al Viro <viro@...iv.linux.org.uk>, Hugh Dickins <hughd@...gle.com>,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	Andi Kleen <ak@...ux.intel.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	Hillf Danton <dhillf@...il.com>, Dave Hansen <dave@...1.net>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Ning Qu <quning@...gle.com>
Subject: [PATCH 04/12] mm, thp, tmpfs: split huge page when moving from page
 cache to swap

in shmem_writepage, we have to split the huge page when moving pages
from page cache to swap because we don't support huge page in swap
yet.

Signed-off-by: Ning Qu <quning@...il.com>
---
 mm/shmem.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 8fe17dd..68a0e1d 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -898,6 +898,13 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 	swp_entry_t swap;
 	pgoff_t index;
 
+	/* TODO: we have to break the huge page at this point,
+	 * since we have no idea how to recover a huge page from
+	 * swap.
+	 */
+	if (PageTransCompound(page))
+		split_huge_page(compound_trans_head(page));
+
 	BUG_ON(!PageLocked(page));
 	mapping = page->mapping;
 	index = page->index;
@@ -946,7 +953,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 			if (shmem_falloc)
 				goto redirty;
 		}
-		clear_highpage(page);
+		clear_pagecache_page(page);
 		flush_dcache_page(page);
 		SetPageUptodate(page);
 	}
-- 
1.8.4


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