linux-ext4 - [RFC PATCH 2/2] jbd: Stabilize pages during writes when in ordered mode

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Message-ID: <20121122023645.GB32182@blackbox.djwong.org>
Date:	Wed, 21 Nov 2012 18:36:45 -0800
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	NeilBrown <neilb@...e.de>
Cc:	Jan Kara <jack@...e.cz>, axboe@...nel.dk, lucho@...kov.net,
	ericvh@...il.com, tytso@....edu, rminnich@...dia.gov,
	viro@...iv.linux.org.uk, martin.petersen@...cle.com,
	david@...morbit.com, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, adilger.kernel@...ger.ca,
	bharrosh@...asas.com, jlayton@...ba.org,
	v9fs-developer@...ts.sourceforge.net, linux-ext4@...r.kernel.org
Subject: [RFC PATCH 2/2] jbd: Stabilize pages during writes when in ordered
 mode

When writing buffers out to disk ahead of committing a transaction, set the
Stable bit on the page to prevent others from wandering in and modifying the
page.

Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
---
 fs/jbd/commit.c |   18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index 86b39b1..b1f0eed 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -155,13 +155,29 @@ static int journal_write_commit_record(journal_t *journal,
 	return (ret == -EIO);
 }
 
+static void end_stable_write_sync(struct buffer_head *bh, int uptodate)
+{
+	clear_page_stable(bh->b_page);
+	end_buffer_write_sync(bh, uptodate);
+}
+
 static void journal_do_submit_data(struct buffer_head **wbuf, int bufs,
 				   int write_op)
 {
 	int i;
 
 	for (i = 0; i < bufs; i++) {
-		wbuf[i]->b_end_io = end_buffer_write_sync;
+		struct page *p = wbuf[i]->b_page;
+		if (TestSetPageStable(p))
+			wbuf[i]->b_end_io = end_buffer_write_sync;
+		else
+			wbuf[i]->b_end_io = end_stable_write_sync;
+
+		if (trylock_page(p)) {
+			clear_page_dirty_for_io(p);
+			unlock_page(p);
+		}
+
 		/* We use-up our safety reference in submit_bh() */
 		submit_bh(write_op, wbuf[i]);
 	}
--
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