linux-kernel - [PATCH v2] dma-debug: enhance dma_debug_device

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Date:	Wed, 13 Nov 2013 13:56:08 -0700
From:	Shuah Khan <shuah.kh@...sung.com>
To:	akpm@...ux-foundation.org, alexander.h.duyck@...el.com,
	joro@...tes.org
Cc:	Shuah Khan <shuah.kh@...sung.com>, linux-kernel@...r.kernel.org,
	shuahkhan@...il.com
Subject: [PATCH v2] dma-debug: enhance dma_debug_device_change() to check for mapping errors

dma-debug checks to verify if driver validated the address returned by
dma mapping routines when driver does unmap. If a driver doesn't call
unmap, failure to check mapping errors isn't detected and reported.

Enhancing existing bus notifier_call dma_debug_device_change() to check
for mapping errors at the same time it detects leaked dma buffers for
BUS_NOTIFY_UNBOUND_DRIVER event. It scans for mapping errors and if any
found, prints one warning message that includes mapping error count.

Signed-off-by: Shuah Khan <shuah.kh@...sung.com>
---
 lib/dma-debug.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index d87a17a..e34865e 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -717,6 +717,7 @@ static int device_dma_allocations(struct device *dev, struct dma_debug_entry **o
 	struct dma_debug_entry *entry;
 	unsigned long flags;
 	int count = 0, i;
+	int map_err_cnt = 0;
 
 	local_irq_save(flags);
 
@@ -724,6 +725,8 @@ static int device_dma_allocations(struct device *dev, struct dma_debug_entry **o
 		spin_lock(&dma_entry_hash[i].lock);
 		list_for_each_entry(entry, &dma_entry_hash[i].list, list) {
 			if (entry->dev == dev) {
+				if (entry->map_err_type == MAP_ERR_NOT_CHECKED)
+					map_err_cnt += 1;
 				count += 1;
 				*out_entry = entry;
 			}
@@ -733,6 +736,10 @@ static int device_dma_allocations(struct device *dev, struct dma_debug_entry **o
 
 	local_irq_restore(flags);
 
+	if (map_err_cnt)
+		dev_warn(entry->dev,
+			"DMA-API: device driver failed to check map errors: "
+			"[count] = %d\n", map_err_cnt);
 	return count;
 }
 
-- 
1.8.3.2

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