linux-kernel - [PATCH] VM: kswapd should not do blocking memory allocations

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Date:	Wed, 18 Aug 2010 15:04:01 -0400
From:	Trond Myklebust <Trond.Myklebust@...app.com>
To:	linux-mm@...ck.org
Cc:	linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org
Subject: [PATCH] VM: kswapd should not do blocking memory allocations

From: Trond Myklebust <Trond.Myklebust@...app.com>

Allowing kswapd to do GFP_KERNEL memory allocations (or any blocking memory
allocations) is wrong and can cause deadlocks in try_to_release_page(), as
the filesystem believes it is safe to allocate new memory and block,
whereas kswapd is there specifically to clear a low-memory situation...

Set the gfp_mask to GFP_IOFS instead.

Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
---

 mm/vmscan.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)


diff --git a/mm/vmscan.c b/mm/vmscan.c
index ec5ddcc..716dd16 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2095,7 +2095,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
 	unsigned long total_scanned;
 	struct reclaim_state *reclaim_state = current->reclaim_state;
 	struct scan_control sc = {
-		.gfp_mask = GFP_KERNEL,
+		.gfp_mask = GFP_IOFS,
 		.may_unmap = 1,
 		.may_swap = 1,
 		/*

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