linux-kernel - [PATCH 14/14] mm: Account for WRITEBACK_TEMP in balance_dirty

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Date:	Fri, 16 Nov 2012 21:10:45 +0400
From:	Maxim Patlasov <mpatlasov@...allels.com>
To:	miklos@...redi.hu
Cc:	dev@...allels.com, fuse-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, jbottomley@...allels.com,
	viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
	xemul@...nvz.org
Subject: [PATCH 14/14] mm: Account for WRITEBACK_TEMP in balance_dirty_pages

Make balance_dirty_pages start the throttling when the WRITEBACK_TEMP
counter is high enough. This prevents us from having too many dirty
pages on fuse, thus giving the userspace part of it a chance to write
stuff properly.

Note, that the existing balance logic is per-bdi, i.e. if the fuse
user task gets stuck in the function this means, that it either
writes to the mountpoint it serves (but it can deadlock even without
the writeback) or it is writing to some _other_ dirty bdi and in the
latter case someone else will free the memory for it.

Signed-off-by: Maxim Patlasov <MPatlasov@...allels.com>
Signed-off-by: Pavel Emelyanov <xemul@...nvz.org>
---
 mm/page-writeback.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 830893b..499a606 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1220,7 +1220,8 @@ static void balance_dirty_pages(struct address_space *mapping,
 		 */
 		nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
 					global_page_state(NR_UNSTABLE_NFS);
-		nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK);
+		nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK) +
+			global_page_state(NR_WRITEBACK_TEMP);
 
 		global_dirty_limits(&background_thresh, &dirty_thresh);
 

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