linux-kernel - [PATCH 3/8] ext4: Warn if direct reclaim tries to writeback pages

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Message-Id: <1311265730-5324-4-git-send-email-mgorman@suse.de>
Date:	Thu, 21 Jul 2011 17:28:45 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Linux-MM <linux-mm@...ck.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, XFS <xfs@....sgi.com>,
	Dave Chinner <david@...morbit.com>,
	Christoph Hellwig <hch@...radead.org>,
	Johannes Weiner <jweiner@...hat.com>,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Mel Gorman <mgorman@...e.de>
Subject: [PATCH 3/8] ext4: Warn if direct reclaim tries to writeback pages

Direct reclaim should never writeback pages. Warn if an attempt
is made.

Signed-off-by: Mel Gorman <mgorman@...e.de>
---
 fs/ext4/inode.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index e3126c0..95bb179 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2663,8 +2663,12 @@ static int ext4_writepage(struct page *page,
 		 * We don't want to do block allocation, so redirty
 		 * the page and return.  We may reach here when we do
 		 * a journal commit via journal_submit_inode_data_buffers.
-		 * We can also reach here via shrink_page_list
+		 * We can also reach here via shrink_page_list but it
+		 * should never be for direct reclaim so warn if that
+		 * happens
 		 */
+		WARN_ON_ONCE((current->flags & (PF_MEMALLOC|PF_KSWAPD)) ==
+								PF_MEMALLOC);
 		goto redirty_page;
 	}
 	if (commit_write)
-- 
1.7.3.4

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