linux-kernel - [RFC] [PATCH 2/4] dio: add page locking for direct I/O

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Date:	Thu, 12 Aug 2010 16:59:41 +0900
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	Wu Fengguang <fengguang.wu@...el.com>,
	"Jun'ichi Nomura" <j-nomura@...jp.nec.com>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [RFC] [PATCH 2/4] dio: add page locking for direct I/O

Basically it is user's responsibility to take care of race condition
related to direct I/O, but some events which are out of user's control
(such as memory failure) can happen at any time. So we need to lock and
set/clear PG_writeback flags in dierct I/O code to protect from data loss.

Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
---
 fs/direct-io.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 7600aac..0d0810d 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -439,7 +439,10 @@ static int dio_bio_complete(struct dio *dio, struct bio *bio)
 			struct page *page = bvec[page_no].bv_page;
 
 			if (dio->rw == READ && !PageCompound(page))
-				set_page_dirty_lock(page);
+				set_page_dirty(page);
+			if (dio->rw & WRITE)
+				end_page_writeback(page);
+			unlock_page(page);
 			page_cache_release(page);
 		}
 		bio_put(bio);
@@ -702,11 +705,14 @@ submit_page_section(struct dio *dio, struct page *page,
 {
 	int ret = 0;
 
+	lock_page(page);
+
 	if (dio->rw & WRITE) {
 		/*
 		 * Read accounting is performed in submit_bio()
 		 */
 		task_io_account_write(len);
+		set_page_writeback(page);
 	}
 
 	/*
-- 
1.7.2.1

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