linux-kernel - [PATCH AUTOSEL 4.9 16/24] dma-debug: change allocation mode from GFP_NOWAIT to GFP

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Message-Id: <20220530135211.1937674-16-sashal@kernel.org>
Date:   Mon, 30 May 2022 09:52:03 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Mikulas Patocka <mpatocka@...hat.com>,
        Christoph Hellwig <hch@....de>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.9 16/24] dma-debug: change allocation mode from GFP_NOWAIT to GFP_ATIOMIC

From: Mikulas Patocka <mpatocka@...hat.com>

[ Upstream commit 84bc4f1dbbbb5f8aa68706a96711dccb28b518e5 ]

We observed the error "cacheline tracking ENOMEM, dma-debug disabled"
during a light system load (copying some files). The reason for this error
is that the dma_active_cacheline radix tree uses GFP_NOWAIT allocation -
so it can't access the emergency memory reserves and it fails as soon as
anybody reaches the watermark.

This patch changes GFP_NOWAIT to GFP_ATOMIC, so that it can access the
emergency memory reserves.

Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
Signed-off-by: Christoph Hellwig <hch@....de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 lib/dma-debug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index 4435bec55fb5..baafebabe3ac 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -463,7 +463,7 @@ EXPORT_SYMBOL(debug_dma_dump_mappings);
  * At any time debug_dma_assert_idle() can be called to trigger a
  * warning if any cachelines in the given page are in the active set.
  */
-static RADIX_TREE(dma_active_cacheline, GFP_NOWAIT);
+static RADIX_TREE(dma_active_cacheline, GFP_ATOMIC);
 static DEFINE_SPINLOCK(radix_lock);
 #define ACTIVE_CACHELINE_MAX_OVERLAP ((1 << RADIX_TREE_MAX_TAGS) - 1)
 #define CACHELINE_PER_PAGE_SHIFT (PAGE_SHIFT - L1_CACHE_SHIFT)
-- 
2.35.1